UDP-glucuronosyltransferases (Ugts) are a supergene family of phase II drug-metabolizing enzymes that catalyze the conjugation of numerous hydrophobic small molecules with the UDP-glucuronic acid, converting them into hydrophilic molecules. Here, we report the identification and cloning of the complete zebrafish Ugt gene repertoire. We found that the zebrafish genome contains 45 Ugt genes that can be divided into three families: Ugt1, Ugt2, and Ugt5. Both Ugt1 and Ugt2 have two unlinked clusters: a and b. The Ugt1a, Ugt1b, Ugt2a, and Ugt2b clusters each contain variable and constant regions, similar to that of the protocadherin (Pcdh), immunoglobulin (Ig), and T-cell receptor (Tcr) clusters. Cloning the full-length coding sequences confirmed that each of the variable exons is separately spliced to the set of constant exons within each zebrafish Ugt cluster. Comparative analyses showed that both a and b clusters of the zebrafish Ugt1 and Ugt2 genes have orthologs in other teleosts, suggesting that they may be resulted from the “fish-specific” whole-genome duplication event. The Ugt5 genes are a novel family of Ugt genes that exist in teleosts and amphibians. Their entire open reading frames are encoded by single large exons. The zebrafish Ugt1, Ugt2, and Ugt5 genes can generate additional transcript diversity through alternative splicing. Based on phylogenetic analyses, we propose that the ancestral tetrapod and teleost Ugt1 clusters contained multiple Ugt1 paralogs. After speciation, these ancestral Ugt1 clusters underwent lineage-specific gene loss and duplication. The ancestral vertebrate Ugt2 cluster also underwent lineage-specific duplication. The intronless Ugt5 open reading frames may be derived from retrotransposition followed by gene duplication. They have been expanded dramatically in teleosts and have become the most abundant Ugt family in these lineages. These findings have interesting implications regarding the molecular evolution of genes with diversified variable exons in vertebrates.
Genome sequencing of basidiomycetes, a group of fungi capable of degrading/mineralizing plant material, revealed the presence of numerous cytochrome P450 monooxygenases (P450s) in their genomes, with some exceptions. Considering the large repertoire of P450s found in fungi, it is difficult to identify P450s that play an important role in fungal metabolism and the adaptation of fungi to diverse ecological niches. In this study, we followed Sir Charles Darwin’s theory of natural selection to identify such P450s in model basidiomycete fungi showing a preference for different types of plant components degradation. Any P450 family comprising a large number of member P450s compared to other P450 families indicates its natural selection over other P450 families by its important role in fungal physiology. Genome-wide comparative P450 analysis in the basidiomycete species, Phanerochaete chrysosporium, Phanerochaete carnosa, Agaricus bisporus, Postia placenta, Ganoderma sp. and Serpula lacrymans, revealed enrichment of 11 P450 families (out of 68 P450 families), CYP63, CYP512, CYP5035, CYP5037, CYP5136, CYP5141, CYP5144, CYP5146, CYP5150, CYP5348 and CYP5359. Phylogenetic analysis of the P450 family showed species-specific alignment of P450s across the P450 families with the exception of P450s of Phanerochaete chrysosporium and Phanerochaete carnosa, suggesting paralogous evolution of P450s in model basidiomycetes. P450 gene-structure analysis revealed high conservation in the size of exons and the location of introns. P450s with the same gene structure were found tandemly arranged in the genomes of selected fungi. This clearly suggests that extensive gene duplications, particularly tandem gene duplications, led to the enrichment of selective P450 families in basidiomycetes. Functional analysis and gene expression profiling data suggest that members of the P450 families are catalytically versatile and possibly involved in fungal colonization of plant material. To our knowledge, this is the first report on the identification and comparative-evolutionary analysis of P450 families enriched in model basidiomycetes.
Lignans are a class of diphenolic nonsteroidal phytoestrogens often found glycosylated in planta. Flax seeds are a rich source of secoisolariciresinol diglucoside (SDG) lignans. Glycosylation is a process by which a glycosyl group is covalently attached to an aglycone substrate and is catalyzed by uridine diphosphate glycosyltransferases (UGTs). Until now, very little information was available on UGT genes that may play a role in flax SDG biosynthesis. Here we report on the identification, structural and functional characterization of 5 putative UGTs potentially involved in secoisolariciresinol (SECO) glucosylation in flax.
Five UGT genes belonging to the glycosyltransferases’ family 1 (EC 2.4.x.y) were cloned and characterized. They fall under four UGT families corresponding to five sub-families referred to as UGT74S1, UGT74T1, UGT89B3, UGT94H1, UGT712B1 that all display the characteristic plant secondary product glycosyltransferase (PSPG) conserved motif. However, diversity was observed within this 44 amino acid sequence, especially in the two peptide sequences WAPQV and HCGWNS known to play a key role in the recognition and binding of diverse aglycone substrates and in the sugar donor specificity. In developing flax seeds, UGT74S1 and UGT94H1 showed a coordinated gene expression with that of pinoresinol-lariciresinol reductase (PLR) and their gene expression patterns correlated with SDG biosynthesis. Enzyme assays of the five heterologously expressed UGTs identified UGT74S1 as the only one using SECO as substrate, forming SECO monoglucoside (SMG) and then SDG in a sequential manner.
We have cloned and characterized five flax UGTs and provided evidence that UGT74S1 uses SECO as substrate to form SDG in vitro. This study allowed us to propose a model for the missing step in SDG lignan biosynthesis.
Flax; Lignan; UGTs; SDG; Secoisolariciresinol; Glucosylation; Glycosyltranferases
The domestic cat (Felis catus) shows remarkable sensitivity to
the adverse effects of phenolic drugs, including acetaminophen and aspirin, as
well as structurally-related toxicants found in the diet and environment. This
idiosyncrasy results from pseudogenization of the gene encoding
UDP-glucuronosyltransferase (UGT) 1A6, the major species-conserved phenol
detoxification enzyme. Here, we established the phylogenetic timing of
disruptive UGT1A6 mutations and explored the hypothesis that
gene inactivation in cats was enabled by minimal exposure to plant-derived
toxicants. Fixation of the UGT1A6 pseudogene was estimated to
have occurred between 35 and 11 million years ago with all extant Felidae having
dysfunctional UGT1A6. Out of 22 additional taxa sampled,
representative of most Carnivora families, only brown hyena (Parahyaena
brunnea) and northern elephant seal (Mirounga
angustirostris) showed inactivating UGT1A6
mutations. A comprehensive literature review of the natural diet of the sampled
taxa indicated that all species with defective UGT1A6 were
hypercarnivores (>70% dietary animal matter). Furthermore those
species with UGT1A6 defects showed evidence for reduced amino
acid constraint (increased dN/dS ratios approaching the neutral
selection value of 1.0) as compared with species with intact
UGT1A6. In contrast, there was no evidence for reduced
amino acid constraint for these same species within UGT1A1, the
gene encoding the enzyme responsible for detoxification of endogenously
generated bilirubin. Our results provide the first evidence suggesting that diet
may have played a permissive role in the devolution of a mammalian drug
metabolizing enzyme. Further work is needed to establish whether these
preliminary findings can be generalized to all Carnivora.
Cytochrome P450 monooxygenases (CYPs/P450s) are heme-thiolate proteins whose role as a drug target against pathogenic microbes has been explored because of their stereo- and regio-specific oxidation activity. We aimed to assess the CYP53 family's role as a common alternative drug target against animal (including human) and plant pathogenic fungi and its role in fungal-mediated wood degradation. Genome-wide analysis of fungal species revealed the presence of CYP53 members in ascomycetes and basidiomycetes. Basidiomycetes had a higher number of CYP53 members in their genomes than ascomycetes. Only two CYP53 subfamilies were found in ascomycetes and six subfamilies in basidiomycetes, suggesting that during the divergence of phyla ascomycetes lost CYP53 P450s. According to phylogenetic and gene-structure analysis, enrichment of CYP53 P450s in basidiomycetes occurred due to the extensive duplication of CYP53 P450s in their genomes. Numerous amino acids (103) were found to be conserved in the ascomycetes CYP53 P450s, against only seven in basidiomycetes CYP53 P450s. 3D-modelling and active-site cavity mapping data revealed that the ascomycetes CYP53 P450s have a highly conserved protein structure whereby 78% amino acids in the active-site cavity were found to be conserved. Because of this rigid nature of ascomycetes CYP53 P450s' active site cavity, any inhibitor directed against this P450 family can serve as a common anti-fungal drug target, particularly toward pathogenic ascomycetes. The dynamic nature of basidiomycetes CYP53 P450s at a gene and protein level indicates that these P450s are destined to acquire novel functions. Functional analysis of CYP53 P450s strongly supported our hypothesis that the ascomycetes CYP53 P450s ability is limited for detoxification of toxic molecules, whereas basidiomycetes CYP53 P450s play an additional role, i.e. involvement in degradation of wood and its derived components. This study is the first report on genome-wide comparative structural (gene and protein structure-level) and evolutionary analysis of a fungal P450 family.
The glycosylation process, catalyzed by ubiquitous glycosyltransferase (GT) family enzymes, is a prevalent modification of plant secondary metabolites that regulates various functions such as hormone homeostasis, detoxification of xenobiotics and biosynthesis and storage of secondary metabolites. Flax (Linum usitatissimum L.) is a commercially grown oilseed crop, important because of its essential fatty acids and health promoting lignans. Identification and characterization of UDP glycosyltransferase (UGT) genes from flax could provide valuable basic information about this important gene family and help to explain the seed specific glycosylated metabolite accumulation and other processes in plants. Plant genome sequencing projects are useful to discover complexity within this gene family and also pave way for the development of functional genomics approaches.
Taking advantage of the newly assembled draft genome sequence of flax, we identified 137 UDP glycosyltransferase (UGT) genes from flax using a conserved signature motif. Phylogenetic analysis of these protein sequences clustered them into 14 major groups (A-N). Expression patterns of these genes were investigated using publicly available expressed sequence tag (EST), microarray data and reverse transcription quantitative real time PCR (RT-qPCR). Seventy-three per cent of these genes (100 out of 137) showed expression evidence in 15 tissues examined and indicated varied expression profiles. The RT-qPCR results of 10 selected genes were also coherent with the digital expression analysis. Interestingly, five duplicated UGT genes were identified, which showed differential expression in various tissues. Of the seven intron loss/gain positions detected, two intron positions were conserved among most of the UGTs, although a clear relationship about the evolution of these genes could not be established. Comparison of the flax UGTs with orthologs from four other sequenced dicot genomes indicated that seven UGTs were flax diverged.
Flax has a large number of UGT genes including few flax diverged ones. Phylogenetic analysis and expression profiles of these genes identified tissue and condition specific repertoire of UGT genes from this crop. This study would facilitate precise selection of candidate genes and their further characterization of substrate specificities and in planta functions.
We have developed a new primer design strategy for PCR amplification of distantly related gene sequences based on consensus-degenerate hybrid oligonucleotide primers (CODEHOPs). An interactive program has been written to design CODEHOP PCR primers from conserved blocks of amino acids within multiply-aligned protein sequences. Each CODEHOP consists of a pool of related primers containing all possible nucleotide sequences encoding 3–4 highly conserved amino acids within a 3′ degenerate core. A longer 5′ non-degenerate clamp region contains the most probable nucleotide predicted for each flanking codon. CODEHOPs are used in PCR amplification to isolate distantly related sequences encoding the conserved amino acid sequence. The primer design software and the CODEHOP PCR strategy have been utilized for the identification and characterization of new gene orthologs and paralogs in different plant, animal and bacterial species. In addition, this approach has been successful in identifying new pathogen species. The CODEHOP designer (http://blocks.fhcrc.org/codehop.html) is linked to BlockMaker and the Multiple Alignment Processor within the Blocks Database World Wide Web (http://blocks.fhcrc.org).
The human genome contains a large number of gene clusters with multiple-variable-first exons, including the drug-metabolizing UDP glucuronosyltransferase (UGT1) and I-branching β-1,6-N-acetylglucosaminyltransferase (GCNT2, also known as IGNT) clusters, organized in a tandem array, similar to that of the protocadherin (PCDH), immunoglobulin (IG), and T-cell receptor (TCR) clusters. To gain insight into the evolutionary processes that may have shaped their diversity, we performed comprehensive comparative analyses for vertebrate multiple-variable-first-exon clusters.
We found that there are species-specific variable-exon duplications and mutations in the vertebrate Ugt1, Gcnt2, and Ugt2a clusters and that their variable and constant genomic organizations are conserved and vertebrate-specific. In addition, analyzing the complete repertoires of closely-related Ugt2 clusters in humans, mice, and rats revealed extensive lineage-specific duplications. In contrast to the Pcdh gene clusters, gene conversion does not play a predominant role in the evolution of the vertebrate Ugt1, Gcnt2 and Ugt2 gene clusters. Thus, their tremendous diversity is achieved through "birth-and-death" evolution. Comparative analyses and homologous modeling demonstrated that vertebrate UGT proteins have similar three-dimensional structures each with N-terminal and C-terminal Rossmann-fold domains binding acceptor and donor substrates, respectively. Molecular docking experiments identified key residues in donor and acceptor recognition and provided insight into the catalytic mechanism of UGT glucuronidation, suggesting the human UGT1A1 residue histidine 39 (H39) as a general base and the residue aspartic acid 151 (D151) as an important electron-transfer helper. In addition, we identified four hypervariable regions in the N-terminal Rossmann domain that form an acceptor-binding pocket. Finally, analyzing patterns of nonsynonymous and synonymous nucleotide substitutions identified codon sites that are subject to positive Darwinian selection at the molecular level. These diversified residues likely play an important role in recognition of myriad xenobiotics and endobiotics.
Our results suggest that enormous diversity of vertebrate multiple variable first exons is achieved through birth-and-death evolution and that adaptive evolution of specific codon sites enhances vertebrate UGT diversity for defense against environmental agents. Our results also have interesting implications regarding the staggering molecular diversity required for chemical detoxification and drug clearance.
As a major component of plant cell wall, lignin plays important roles in mechanical support, water transport, and stress responses. As the main cause for the recalcitrance of plant cell wall, lignin modification has been a major task for bioenergy feedstock improvement. The study of the evolution and function of lignin biosynthesis genes thus has two-fold implications. First, the lignin biosynthesis pathway provides an excellent model to study the coordinative evolution of a biochemical pathway in plants. Second, understanding the function and evolution of lignin biosynthesis genes will guide us to develop better strategies for bioenergy feedstock improvement.
We analyzed lignin biosynthesis genes from fourteen plant species and one symbiotic fungal species. Comprehensive comparative genome analysis was carried out to study the distribution, relatedness, and family expansion of the lignin biosynthesis genes across the plant kingdom. In addition, we also analyzed the comparative synteny map between rice and sorghum to study the evolution of lignin biosynthesis genes within the Poaceae family and the chromosome evolution between the two species. Comprehensive lignin biosynthesis gene expression analysis was performed in rice, poplar and Arabidopsis. The representative data from rice indicates that different fates of gene duplications exist for lignin biosynthesis genes. In addition, we also carried out the biomass composition analysis of nine Arabidopsis mutants with both MBMS analysis and traditional wet chemistry methods. The results were analyzed together with the genomics analysis.
The research revealed that, among the species analyzed, the complete lignin biosynthesis pathway first appeared in moss; the pathway is absent in green algae. The expansion of lignin biosynthesis gene families correlates with substrate diversity. In addition, we found that the expansion of the gene families mostly occurred after the divergence of monocots and dicots, with the exception of the C4H gene family. Gene expression analysis revealed different fates of gene duplications, largely confirming plants are tolerant to gene dosage effects. The rapid expansion of lignin biosynthesis genes indicated that the translation of transgenic lignin modification strategies from model species to bioenergy feedstock might only be successful between the closely relevant species within the same family.
Brassinosteroids (BRs) are growth-promoting steroid hormones that regulate diverse physiological processes in plants. Most BR biosynthetic enzymes belong to the cytochrome P450 (CYP) family. The gene encoding the ultimate step of BR biosynthesis in Arabidopsis likely evolved by gene duplication followed by functional specialization in a dicotyledonous plant-specific manner. To gain insight into the evolution of BRs, we performed a genomic reconstitution of Arabidopsis BR biosynthetic genes in an ancestral vascular plant, the lycophyte Selaginella moellendorffii. Selaginella contains four members of the CYP90 family that cluster together in the CYP85 clan. Similar to known BR biosynthetic genes, the Selaginella CYP90s exhibit eight or ten exons and Selaginella produces a putative BR biosynthetic intermediate. Therefore, we hypothesized that Selaginella CYP90 genes encode BR biosynthetic enzymes. In contrast to typical CYPs in Arabidopsis, Selaginella CYP90E2 and CYP90F1 do not possess amino-terminal signal peptides, suggesting that they do not localize to the endoplasmic reticulum. In addition, one of the three putative CYP reductases (CPRs) that is required for CYP enzyme function co-localized with CYP90E2 and CYP90F1. Treatments with a BR biosynthetic inhibitor, propiconazole, and epi-brassinolide resulted in greatly retarded and increased growth, respectively. This suggests that BRs promote growth in Selaginella, as they do in Arabidopsis. However, BR signaling occurs through different pathways than in Arabidopsis. A sequence homologous to the Arabidopsis BR receptor BRI1 was absent in Selaginella, but downstream components, including BIN2, BSU1, and BZR1, were present. Thus, the mechanism that initiates BR signaling in Selaginella seems to differ from that in Arabidopsis. Our findings suggest that the basic physiological roles of BRs as growth-promoting hormones are conserved in both lycophytes and Arabidopsis; however, different BR molecules and BRI1-based membrane receptor complexes evolved in these plants.
Increasing use of zebrafish in drug discovery and mechanistic toxicology demands knowledge of cytochrome P450 (CYP) gene regulation and function. CYP enzymes catalyze oxidative transformation leading to activation or inactivation of many endogenous and exogenous chemicals, with consequences for normal physiology and disease processes. Many CYPs potentially have roles in developmental specification, and many chemicals that cause developmental abnormalities are substrates for CYPs. Here we identify and annotate the full suite of CYP genes in zebrafish, compare these to the human CYP gene complement, and determine the expression of CYP genes during normal development.
Zebrafish have a total of 94 CYP genes, distributed among 18 gene families found also in mammals. There are 32 genes in CYP families 5 to 51, most of which are direct orthologs of human CYPs that are involved in endogenous functions including synthesis or inactivation of regulatory molecules. The high degree of sequence similarity suggests conservation of enzyme activities for these CYPs, confirmed in reports for some steroidogenic enzymes (e.g. CYP19, aromatase; CYP11A, P450scc; CYP17, steroid 17a-hydroxylase), and the CYP26 retinoic acid hydroxylases. Complexity is much greater in gene families 1, 2, and 3, which include CYPs prominent in metabolism of drugs and pollutants, as well as of endogenous substrates. There are orthologous relationships for some CYP1 s and some CYP3 s between zebrafish and human. In contrast, zebrafish have 47 CYP2 genes, compared to 16 in human, with only two (CYP2R1 and CYP2U1) recognized as orthologous based on sequence. Analysis of shared synteny identified CYP2 gene clusters evolutionarily related to mammalian CYP2 s, as well as unique clusters.
Transcript profiling by microarray and quantitative PCR revealed that the majority of zebrafish CYP genes are expressed in embryos, with waves of expression of different sets of genes over the course of development. Transcripts of some CYP occur also in oocytes. The results provide a foundation for the use of zebrafish as a model in toxicological, pharmacological and chemical disease research.
Brassinosteroids (BRs) are signaling molecules that play essential roles in the spatial regulation of plant growth and development. In contrast to other plant hormones BRs act locally, close to the sites of their synthesis, and thus homeostatic mechanisms must operate at the cellular level to equilibrate BR concentrations. Whilst it is recognized that levels of bioactive BRs are likely adjusted by controlling the relative rates of biosynthesis and by catabolism, few factors, which participate in these regulatory events, have as yet been identified. Previously we have shown that the UDP-glycosyltransferase UGT73C5 of Arabidopsis thaliana catalyzes 23-O-glucosylation of BRs and that glucosylation renders BRs inactive. This study identifies the closest homologue of UGT73C5, UGT73C6, as an enzyme that is also able to glucosylate BRs in planta.
In a candidate gene approach, in which homologues of UGT73C5 were screened for their potential to induce BR deficiency when over-expressed in plants, UGT73C6 was identified as an enzyme that can glucosylate the BRs CS and BL at their 23-O-positions in planta. GUS reporter analysis indicates that UGT73C6 shows over-lapping, but also distinct expression patterns with UGT73C5 and YFP reporter data suggests that at the cellular level, both UGTs localize to the cytoplasm and to the nucleus. A liquid chromatography high-resolution mass spectrometry method for BR metabolite analysis was developed and applied to determine the kinetics of formation and the catabolic fate of BR-23-O-glucosides in wild type and UGT73C5 and UGT73C6 over-expression lines. This approach identified novel BR catabolites, which are considered to be BR-malonylglucosides, and provided first evidence indicating that glucosylation protects BRs from cellular removal. The physiological significance of BR glucosylation, and the possible role of UGT73C6 as a regulatory factor in this process are discussed in light of the results presented.
The present study generates essential knowledge and molecular and biochemical tools, that will allow for the verification of a potential physiological role of UGT73C6 in BR glucosylation and will facilitate the investigation of the functional significance of BR glucoside formation in plants.
arabidopsis; brassinosteroids; glycosylation; homeostasis; malonylation; steroids
Consensus-degenerate hybrid oligonucleotide primers (CODEHOPs) have proven to be a powerful tool for the identification of novel genes. CODEHOPs are designed from highly conserved regions of multiply-aligned protein sequences from members of a gene family and are used in PCR amplification to identify distantly-related genes. The CODEHOP approach has been used to identify novel pathogens by targeting amino acid motifs conserved in specific pathogen families. We initiated a program utilizing the CODEHOP approach to develop PCR-based assays targeting a variety of viral families that are pathogens in non-human primates. We have also developed and further improved a computer program and website to facilitate the design of CODEHOP PCR primers. Here, we detail the method for the development of pathogen-specific CODEHOP PCR assays using the papillomavirus family as a target. Papillomaviruses constitute a diverse virus family infecting a wide variety of mammalian species, including humans and non-human primates. We demonstrate that our pan-papillomavirus CODEHOP assay is broadly reactive with all major branches of the virus family and show its utility in identifying a novel non-human primate papillomavirus in cynomolgus macaques.
polymerase chain reaction; consensus; degenerate; oligonucleotide; primers; pathogens; virus; non-human primate; papillomavirus
Cytochrome P450 (CYP) monooxygenase superfamily contributes a broad array of biological functions in living organisms. In fungi, CYPs play diverse and pivotal roles in versatile metabolism and fungal adaptation to specific ecological niches. In this report, CYPomes in the 47 genomes of fungi belong to the phyla Ascomycota, Basidiomycota, Chytridiomycota, and Zygomycota have been studied. The comparison of fungal CYPomes suggests that generally fungi possess abundant CYPs belonging to a variety of families with the two global families CYP51 and CYP61, indicating individuation of CYPomes during the evolution of fungi. Fungal CYPs show highly conserved characteristic motifs, but very low overall sequence similarities. The characteristic motifs of fungal CYPs are distinguishable from those of CYPs in animals, plants, and especially archaea and bacteria. The four representative motifs contribute to the general function of CYPs. Fungal CYP51s and CYP61s can be used as the models for the substrate recognition sites analysis. The CYP proteins are clustered into 15 clades and the phylogenetic analyses suggest that the wide variety of fungal CYPs has mainly arisen from gene duplication. Two large duplication events might have been associated with the booming of Ascomycota and Basidiomycota. In addition, horizontal gene transfer also contributes to the diversification of fungal CYPs. Finally, a possible evolutionary scenario for fungal CYPs along with fungal divergences is proposed. Our results provide the fundamental information for a better understanding of CYP distribution, structure and function, and new insights into the evolutionary events of fungal CYPs along with the evolution of fungi.
cytochrome P450; characteristic motif; fungi; evolution; duplication
Xanthophylls, oxygenated derivatives of carotenes, play critical roles in photosynthetic apparatus of cyanobacteria, algae, and higher plants. Although the xanthophylls biosynthetic pathway of algae is largely unknown, it is of particular interest because they have a very complicated evolutionary history. Carotenoid hydroxylase (CHY) is an important protein that plays essential roles in xanthophylls biosynthesis. With the availability of 18 sequenced algal genomes, we performed a comprehensive comparative analysis of chy genes and explored their distribution, structure, evolution, origins, and expression.
Overall 60 putative chy genes were identified and classified into two major subfamilies (bch and cyp97) according to their domain structures. Genes in the bch subfamily were found in 10 green algae and 1 red alga, but absent in other algae. In the phylogenetic tree, bch genes of green algae and higher plants share a common ancestor and are of non-cyanobacterial origin, whereas that of red algae is of cyanobacteria. The homologs of cyp97a/c genes were widespread only in green algae, while cyp97b paralogs were seen in most of algae. Phylogenetic analysis on cyp97 genes supported the hypothesis that cyp97b is an ancient gene originated before the formation of extant algal groups. The cyp97a gene is more closely related to cyp97c in evolution than to cyp97b. The two cyp97 genes were isolated from the green alga Haematococcus pluvialis, and transcriptional expression profiles of chy genes were observed under high light stress of different wavelength.
Green algae received a β-xanthophylls biosynthetic pathway from host organisms. Although red algae inherited the pathway from cyanobacteria during primary endosymbiosis, it remains unclear in Chromalveolates. The α-xanthophylls biosynthetic pathway is a common feature in green algae and higher plants. The origination of cyp97a/c is most likely due to gene duplication before divergence of green algae and higher plants. Protein domain structures and expression analyses in green alga H. pluvialis indicate that various chy genes are in different manners response to light. The knowledge of evolution of chy genes in photosynthetic eukaryotes provided information of gene cloning and functional investigation of chy genes in algae in the future.
Carotenoid hydroxylase; Xanthophylls biosynthesis; Structure and evolution; Molecular cloning; Expression profiles; Algae
Phanerochaete chrysosporium, the model white rot basidiomycetous fungus, has the extraordinary ability to mineralize (to CO2) lignin and detoxify a variety of chemical pollutants. Its cytochrome P450 monooxygenases have recently been implied in several of these biotransformations. Our initial P450 cloning efforts in P. chrysosporium and its subsequent whole genome sequencing have revealed an extraordinary P450 repertoire ("P450ome") containing at least 150 P450 genes with yet unknown function. In order to understand the functional diversity and the evolutionary mechanisms and significance of these hemeproteins, here we report a genome-wide structural and evolutionary analysis of the P450ome of this fungus.
Our analysis showed that P. chrysosporium P450ome could be classified into 12 families and 23 sub-families and is characterized by the presence of multigene families. A genome-level structural analysis revealed 16 organizationally homogeneous and heterogeneous clusters of tandem P450 genes. Analysis of our cloned cDNAs revealed structurally conserved characteristics (intron numbers and locations, and functional domains) among members of the two representative multigene P450 families CYP63 and CYP505 (P450foxy). Considering the unusually complex structural features of the P450 genes in this genome, including microexons (2–10 aa) and frequent small introns (45–55 bp), alternative splicing, as experimentally observed for CYP63, may be a more widespread event in the P450ome of this fungus. Clan-level phylogenetic comparison revealed that P. chrysosporium P450 families fall under 11 fungal clans and the majority of these multigene families appear to have evolved locally in this genome from their respective progenitor genes, as a result of extensive gene duplications and rearrangements.
P. chrysosporium P450ome, the largest known todate among fungi, is characterized by tandem gene clusters and multigene families. This enormous P450 gene diversity has evolved by extensive gene duplications and intragenomic recombinations of the progenitor genes presumably to meet the exceptionally high metabolic demand of this biodegradative group of basidiomycetous fungi in ecological niches. In this context, alternative splicing appears to further contribute to the evolution of functional diversity of the P450ome in this fungus. The evolved P450 diversity is consistent with the known vast biotransformation potential of P. chrysosporium. The presented analysis will help design future P450 functional studies to understand the underlying mechanisms of secondary metabolism and oxidative biotransformation pathways in this model white rot fungus.
The cytochrome P450 (CYP) superfamily is a multifunctional hemethiolate enzyme that is widely distributed from Bacteria to Eukarya. The CYP3 family contains mainly the four subfamilies CYP3A, CYP3B, CYP3C and CYP3D in vertebrates; however, only the Actinopterygii (ray-finned fish) have all four subfamilies and detailed understanding of the evolutionary relationship of Actinopterygii CYP3 family members would be valuable.
Methods and Findings
Phylogenetic relationships were constructed to trace the evolutionary history of the Actinopterygii CYP3 family genes. Selection analysis, relative rate tests and functional divergence analysis were combined to interpret the relationship of the site-specific evolution and functional divergence in the Actinopterygii CYP3 family. The results showed that the four CYP3 subfamilies in Actinopterygii might be formed by gene duplication. The first gene duplication event was responsible for divergence of the CYP3B/C clusters from ancient CYP3 before the origin of the Actinopterygii, which corresponded to the fish-specific whole genome duplication (WGD). Tandem repeat duplication in each of the homologue clusters produced stable CYP3B, CYP3C, CYP3A and CYP3D subfamilies. Acceleration of asymmetric evolutionary rates and purifying selection together were the main force for the production of new subfamilies and functional divergence in the new subset after gene duplication, whereas positive selection was detected only in the retained CYP3A subfamily. Furthermore, nearly half of the functional divergence sites appear to be related to substrate recognition, which suggests that site-specific evolution is closely related with functional divergence in the Actinopterygii CYP3 family.
The split of fish-specific CYP3 subfamilies was related to the fish-specific WGD, and site-specific acceleration of asymmetric evolutionary rates and purifying selection was the main force for the origin of the new subfamilies and functional divergence in the new subset after gene duplication. Site-specific evolution in substrate recognition was related to functional divergence in the Actinopterygii CYP3 family.
The neighbourhoods of cytochrome P450 (CYP) genes in deuterostome genomes, as well as those of the cnidarians Nematostella vectensis and Acropora digitifera and the placozoan Trichoplax adhaerens were examined to find clues concerning the evolution of CYP genes in animals. CYP genes created by the 2R whole genome duplications in chordates have been identified. Both microsynteny and macrosynteny were used to identify genes that coexisted near CYP genes in the animal ancestor. We show that all 11 CYP clans began in a common gene environment. The evidence implies the existence of a single locus, which we term the ‘cytochrome P450 genesis locus’, where one progenitor CYP gene duplicated to create a tandem set of genes that were precursors of the 11 animal CYP clans: CYP Clans 2, 3, 4, 7, 19, 20, 26, 46, 51, 74 and mitochondrial. These early CYP genes existed side by side before the origin of cnidarians, possibly with a few additional genes interspersed. The Hox gene cluster, WNT genes, an NK gene cluster and at least one ARF gene were close neighbours to this original CYP locus. According to this evolutionary scenario, the CYP74 clan originated from animals and not from land plants nor from a common ancestor of plants and animals. The CYP7 and CYP19 families that are chordate-specific belong to CYP clans that seem to have originated in the CYP genesis locus as well, even though this requires many gene losses to explain their current distribution. The approach to uncovering the CYP genesis locus overcomes confounding effects because of gene conversion, sequence divergence, gene birth and death, and opens the way to understanding the biodiversity of CYP genes, families and subfamilies, which in animals has been obscured by more than 600 Myr of evolution.
cytochrome P450; ohnologues; evolution; animal P450s; synteny; CYP clans
Sucrose phosphate synthase (SPS) is an important component of the plant sucrose biosynthesis pathway. In the monocotyledonous Poaceae, five SPS genes have been identified. Here we present a detailed analysis of the wheat SPSII family in wheat. A set of homoeologue-specific primers was developed in order to permit both the detection of sequence variation, and the dissection of the individual contribution of each homoeologue to the global expression of SPSII.
The expression in bread wheat over the course of development of various sucrose biosynthesis genes monitored on an Affymetrix array showed that the SPS genes were regulated over time and space. SPSII homoeologue-specific assays were used to show that the three homoeologues contributed differentially to the global expression of SPSII. Genetic mapping placed the set of homoeoloci on the short arms of the homoeologous group 3 chromosomes. A resequencing of the A and B genome copies allowed the detection of four haplotypes at each locus. The 3B copy includes an unspliced intron. A comparison of the sequences of the wheat SPSII orthologues present in the diploid progenitors einkorn, goatgrass and Triticum speltoides, as well as in the more distantly related species barley, rice, sorghum and purple false brome demonstrated that intronic sequence was less well conserved than exonic. Comparative sequence and phylogenetic analysis of SPSII gene showed that false purple brome was more similar to Triticeae than to rice. Wheat - rice synteny was found to be perturbed at the SPS region.
The homoeologue-specific assays will be suitable to derive associations between SPS functionality and key phenotypic traits. The amplicon sequences derived from the homoeologue-specific primers are informative regarding the evolution of SPSII in a polyploid context.
Background and Aims
Abscisic acid (ABA) plays crucial roles in plants' responses to abiotic stresses. ABA 8′-hydroxylation controlled by CYP707A genes has been well studied in Arabidopsis and rice, but not in legumes. The aims of the present study were to identify and functionally analyse the soybean CYP707A gene family, and to explore their expression patterns under dehydration and salt stresses.
A complementation experiment was employed to verify the function of soybean CYP707A1a in ABA catabolism. Genomic and cDNA sequences of other soybean CYP707A genes were isolated from the Phytozome database based on soybean CYP707A1a. The structure and phylogenetic relationship of this gene family was further analysed. The expression patterns of soybean CYP707A genes under dehydration and salt stress were analysed via quantitative real-time PCR.
Over-expression of GmCYP707A1a in the atcyp707a2 T-DNA insertion mutant decreased its sensitivity to ABA, indicating that GmCYP707A1a indeed functions as an ABA 8′-hydroxylase in higher plants. The soybean genome contains ten CYP707A genes. Gene structure and phylogenetic analysis showed high conservation of ten GmCYP707A genes to the other CYP707A genes from monocots and dicots. Seed imbibition induced expression of A1a, A1b, A2a, A2b, A2c, A3a and A5 in embryo, and expression of A1a, A1b, A2a and A2b in cotyledon. Dehydration induced expression of A1a, A1b, A2b, A2c, A3a, A3b, A4a, A4b and A5 both in roots and in leaves, whereas rehydration stimulated transcription of A2a, A2b, A3b, A4a and A5 in roots, and only A3b and A5 in leaves. Expression of all soybean CYP707A genes was induced either by short- or by long-term salt stress.
The first biological evidence is provided that GmCYP7071a encodes an ABA 8′-hydroxylase through transgenic studies. Ten soybean GmCYP707A genes were identified, most of them expressed in multiple soybean tissues, and were induced by imbibition, dehydration and salinity.
Abscisic acid; ABA catabolism; Glycine max; CYP707A gene family; drought; salt stress
A complete assembled genome sequence of wheat is not yet available. Therefore, model plant systems for wheat are very valuable. Brachypodium distachyon (Brachypodium) is such a system. The WRKY family of transcription factors is one of the most important families of plant transcriptional regulators with members regulating important agronomic traits. Studies of WRKY transcription factors in Brachypodium and wheat therefore promise to lead to new strategies for wheat improvement.
We have identified and manually curated the WRKY transcription factor family from Brachypodium using a pipeline designed to identify all potential WRKY genes. 86 WRKY transcription factors were found, a total higher than all other current databases. We therefore propose that our numbering system (BdWRKY1-BdWRKY86) becomes the standard nomenclature. In the JGI v1.0 assembly of Brachypodium with the MIPS/JGI v1.0 annotation, nine of the transcription factors have no gene model and eleven gene models are probably incorrectly predicted. In total, twenty WRKY transcription factors (23.3%) do not appear to have accurate gene models. To facilitate use of our data, we have produced The Database of Brachypodium distachyon WRKY Transcription Factors. Each WRKY transcription factor has a gene page that includes predicted protein domains from MEME analyses. These conserved protein domains reflect possible input and output domains in signaling. The database also contains a BLAST search function where a large dataset of WRKY transcription factors, published genes, and an extensive set of wheat ESTs can be searched. We also produced a phylogram containing the WRKY transcription factor families from Brachypodium, rice, Arabidopsis, soybean, and Physcomitrella patens, together with published WRKY transcription factors from wheat. This phylogenetic tree provides evidence for orthologues, co-orthologues, and paralogues of Brachypodium WRKY transcription factors.
The description of the WRKY transcription factor family in Brachypodium that we report here provides a framework for functional genomics studies in an important model system. Our database is a resource for both Brachypodium and wheat studies and ultimately projects aimed at improving wheat through manipulation of WRKY transcription factors.
WRKY transcription factor; Brachypodium distachyon; Wheat; Comparative genomics; Database
The P450 enzymes maintain a conserved P450 fold despite a considerable variation in sequence. The P450 family even includes proteins that lack the single conserved cysteine and are therefore no longer haem-thiolate proteins. The mechanisms of successive gene duplications leading to large families in plants and animals are well established. Comparisons of P450 CYP gene clusters in related species illustrate the rapid changes in CYPome sizes. Examples of CYP copy number variation with effects on fitness are emerging, and these provide an opportunity to study the proximal causes of duplication or pseudogenization. Birth and death models can explain the proliferation of CYP genes that is amply illustrated by the sequence of every new genome. Thus, the distribution of P450 diversity within the CYPome of plants and animals, a few families with many genes (P450 blooms) and many families with few genes, follows similar power laws in both groups. A closer look at some families with few genes shows that these, often single member families, are not stable during evolution. The enzymatic prowess of P450 may predispose them to switch back and forth between metabolism of critical structural or signal molecules and metabolism dedicated to environmental response.
P450 sequence diversity; copy number variation; duplication; gene clusters
Abscisic acid (ABA) catabolism is one of the determinants of endogenous ABA levels affecting numerous aspects of plant growth and abiotic-stress responses. The major ABA catabolic pathway is triggered by ABA 8'-hydroxylation catalysed by ABA 8'-hydroxylase, the cytochrome P450 CYP707A family. In this study, the full-length cDNAs of AhCYP707A1 and AhCYP707A2 were cloned and characterized from peanut. Expression analyses showed that AhCYP707A1 and AhCYP707A2 were expressed ubiquitously in peanut roots, stems, and leaves with different transcript accumulation levels, including the higher expression of AhCYP707A1 in roots. The expression of AhCYP707A2 was significantly up-regulated by 20% PEG6000 or 250 mmol/L NaCl in peanut roots, stems, and leaves, whereas the up-regulation of AhCYP707A1 transcript level by PEG6000 or NaCl was observed only in roots instead of leaves and stems. Due to the osmotic and ionic stresses of high concentration of NaCl to plants simultaneously, low concentration of LiCl (30 mmol/L, at which concentration osmotic status of cells is not seriously affected, the toxicity of Li+ being higher than that of Na+) was used to examine whether the effect of NaCl might be related to osmotic or ionic stress. The results revealed visually the susceptibility to osmotic stress and the resistance to salt ions in peanut seedlings. The significant up-regulation of AhCYP707A1, AhCYP707A2 and AhNCED1 transcripts and endogenous ABA levels by PEG6000 or NaCl instead of LiCl, showed that the osmotic stress instead of ionic stress affected the expression of those genes and the biosynthesis of ABA in peanut. The functional expression of AhCYP707A1 cDNA in yeast showed that the microsomal fractions prepared from yeast cell expressing recombinant AhCYP707A1 protein exhibited the catalytic activity of ABA 8'-hydroxylase. These results demonstrate that the expressions of AhCYP707A1 and AhCYP707A2 play an important role in ABA catabolism in peanut, particularly in response to osmotic stress.
An allele of the cytochrome P450 gene, CYP6AE14, named CYP6AE25 (GenBank accession no. EU807990) was isolated from the Asian com borer, Ostrinia fumacalis (Guenée) (Lepidoptera: Pyralidae) by RT-PCR. The cDNA sequence of CYP6AE25 is 2315 bp in length and contains a 1569 nucleotides open reading frame encoding a putative protein with 523 amino acid residues and a predicted molecular weight of 59.95 kDa and a theoretical pI of 8.31. The putative protein contains the classic heme-binding sequence motif F××G×××C×G (residues 451–460) conserved among all P450 enzymes as well as other characteristic motifs of all cytochrome P450s. It shares 52% identity with the previously published sequence of CYP6AE14 (GenBank accession no. DQ986461) from Helicoverpa armigera. Phylogenetic analysis of amino acid sequences from members of various P450 families indicated that CYP6AE25 has a closer phylogenetic relationship with CYP6AE14 and CYP6B1 that are related to metabolism of plant allelochemicals, CYP6D1 which is related to pyrethroid resistance and has a more distant relationship to CYP302A1 and CYP307A1 which are related to synthesis of the insect molting hormones. The expression level of the gene in the adults and immature stages of O. furnacalis by quantitative real-time PCR revealed that CYP6AE25 was expressed in all life stages investigated. The mRNA expression level in 3rd instar larvae was 12.8- and 2.97-fold higher than those in pupae and adults, respectively. The tissue specific expression level of CYP6AE25 was in the order of midgut, malpighian tube and fatty body from high to low but was absent in ovary and brain. The analysis of the CYP6AB25 gene using bioinformatic software is discussed.
cytochrome P450; real-time PCR; bioinformatics
As a step toward exploring a targeted metabolomics approach to personalized warfarin (Coumadin) therapy, we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method capable of quantifying specific enantiomeric (R and S) contributions of warfarin (WAR) and the corresponding hydroxywarfarins (OH-WAR) and glucuronides (-GLUC) generated by cytochrome P450s (CYP) and UDP-glucuronosyltransferases (UGTs), respectively. Evaluation of quality control samples and three commercially available human samples showed that our analytical approach has the ability to measure 24 unique WAR metabolites in human urine. Evaluation of the human data also provides new insights for evaluating WAR toxicity and begins characterizing important UGT metabolic pathways responsible for WAR detoxification. Data revealed the significance of specific metabolites among patients and the corresponding enzymatic capacity to generate these compounds, including the first report of direct WAR glucuronidation. On the basis of total OH-WAR levels, (S)-7-OH-WAR was the predominant metabolite indicating the significance of CYP2C9 in WAR metabolism, although other CYP2C enzymes also contributed to clearance of this isomer. (R)-WAR hydroxylation to OH-WARs was more diverse among the patients as reflected in varying contributions of CYP1A2 and multiple CYP2C enzymes. There was wide variation in the glucuronidation of WAR and the OH-WARs with respect to the compounds and patients. 6- and 7-OH-WAR were primarily (>70%) excreted as glucuronides unlike 4′-OH-WAR and 8-OH-WAR. For all patients, UGT1A1 is likely responsible for 6-O-GLUC production, although UGT1A10 may also contribute in one patient. 7-O-GLUC levels reflected contributions from potentially five different UGT1A enzymes. In all cases, WAR, 4′-OH-WAR, 8-OH-WAR, and the corresponding glucuronides were minor metabolites with respect to the others. Taken together, these data suggest that both P450 and UGT reactions contribute to the generation of excretable products in human urine, thereby generating complex metabolic networks.