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1.  Environmental regulation of sex determination in oil palm: current knowledge and insights from other species 
Annals of Botany  2011;108(8):1529-1537.
The African oil palm (Elaeis guineensis) is a monoecious species of the palm subfamily Arecoideae. It may be qualified as ‘temporally dioecious’ in that it produces functionally unisexual male and female inflorescences in an alternating cycle on the same plant, resulting in an allogamous mode of reproduction. The ‘sex ratio’ of an oil palm stand is influenced by both genetic and environmental factors. In particular, the enhancement of male inflorescence production in response to water stress has been well documented.
This paper presents a review of our current understanding of the sex determination process in oil palm and discusses possible insights that can be gained from other species. Although some informative phenological studies have been carried out, nothing is as yet known about the genetic basis of sex determination in oil palm, nor the mechanisms by which this process is regulated. Nevertheless new genomics-based techniques, when combined with field studies and biochemical and molecular cytological-based approaches, should provide a new understanding of the complex processes governing oil palm sex determination in the foreseeable future. Current hypotheses and strategies for future research are discussed.
PMCID: PMC3219494  PMID: 21712294
Sex determination; oil palm; Elaeis guineensis; inflorescence; monoecious; temporal dioecy; flowering
2.  Phylogenetic utility of the nuclear genes AGAMOUS 1 and PHYTOCHROME B in palms (Arecaceae): an example within Bactridinae 
Annals of Botany  2011;108(8):1433-1444.
Background and Aims
Molecular phylogenetic studies of palms (Arecaceae) have not yet provided a fully resolved phylogeny of the family. There is a need to increase the current set of markers to resolve difficult groups such as the Neotropical subtribe Bactridinae (Arecoideae: Cocoseae). We propose the use of two single-copy nuclear genes as valuable tools for palm phylogenetics.
New primers were developed for the amplification of the AGAMOUS 1 (AG1) and PHYTOCHROME B (PHYB) genes. For the AGAMOUS gene, the paralogue 1 of Elaeis guineensis (EgAG1) was targeted. The region amplified contained coding sequences between the MIKC K and C MADS-box domains. For the PHYB gene, exon 1 (partial sequence) was first amplified in palm species using published degenerate primers for Poaceae, and then specific palm primers were designed. The two gene portions were sequenced in 22 species of palms representing all genera of Bactridinae, with emphasis on Astrocaryum and Hexopetion, the status of the latter genus still being debated.
Key Results
The new primers designed allow consistent amplification and high-quality sequencing within the palm family. The two loci studied produced more variability than chloroplast loci and equally or less variability than PRK, RPBII and ITS nuclear markers. The phylogenetic structure obtained with AG1 and PHYB genes provides new insights into intergeneric relationships within the Bactridinae and the intrageneric structure of Astrocaryum. The Hexopetion clade was recovered as monophyletic with both markers and was weakly supported as sister to Astrocaryum sensu stricto in the combined analysis. The rare Astrocaryum minus formed a species complex with Astrocaryum gynacanthum. Moreover, both AG1 and PHYB contain a microsatellite that could have further uses in species delimitation and population genetics.
AG1 and PHYB provide additional phylogenetic information within the palm family, and should prove useful in combination with other genes to improve the resolution of palm phylogenies.
PMCID: PMC3219496  PMID: 21828068
AGAMOUS 1; PHYTOCHROME B; phylogenetic markers; microsatellite; palms; Arecaceae; Bactridinae; Acrocomia; Aiphanes; Astrocaryum; Bactris; Desmoncus; Hexopetion
3.  Insights from ANA-grade angiosperms into the early evolution of CUP-SHAPED COTYLEDON genes 
Annals of Botany  2011;107(9):1511-1519.
Background and Aims
The closely related NAC family genes NO APICAL MERISTEM (NAM) and CUP-SHAPED COTYLEDON3 (CUC3) regulate the formation of boundaries within and between plant organs. NAM is post-transcriptionally regulated by miR164, whereas CUC3 is not. To gain insight into the evolution of NAM and CUC3 in the angiosperms, we analysed orthologous genes in early-diverging ANA-grade angiosperms and gymnosperms.
We obtained NAM- and CUC3-like sequences from diverse angiosperms and gymnosperms by a combination of reverse transcriptase PCR, cDNA library screening and database searching, and then investigated their phylogenetic relationships by performing maximum-likelihood reconstructions. We also studied the spatial expression patterns of NAM, CUC3 and MIR164 orthologues in female reproductive tissues of Amborella trichopoda, the probable sister to all other flowering plants.
Key Results
Separate NAM and CUC3 orthologues were found in early-diverging angiosperms, but not in gymnosperms, which contained putative orthologues of the entire NAM + CUC3 clade that possessed sites of regulation by miR164. Multiple paralogues of NAM or CUC3 genes were noted in certain taxa, including Brassicaceae. Expression of NAM, CUC3 and MIR164 orthologues from Am. trichopoda was found to co-localize in ovules at the developmental boundary between the chalaza and nucellus.
The NAM and CUC3 lineages were generated by duplication, and CUC3 was subsequently lost regulation by miR164, prior to the last common ancestor of the extant angiosperms. However, the paralogous NAM clade genes CUC1 and CUC2 were generated by a more recent duplication, near the base of Brassicaceae. The function of NAM and CUC3 in defining a developmental boundary in the ovule appears to have been conserved since the last common ancestor of the flowering plants, as does the post-transcriptional regulation in ovule tissues of NAM by miR164.
PMCID: PMC3108802  PMID: 21320879
CUP-SHAPED COTYLEDON; CUC; NO APICAL MERISTEM; NAM; NAC; MIR164; Amborella trichopoda; Cabomba aquatica; Ginkgo biloba; angiosperm; gymnosperm
4.  Cell cycle arrest characterizes the transition from a bisexual floral bud to a unisexual flower in Phoenix dactylifera 
Annals of Botany  2010;106(2):255-266.
Background and Aims
Phoenix dactylifera (date palm) is a dioecious species displaying strong dimorphism between pistillate and staminate flowers. The mechanisms involved in the development of unisexual flowers are as yet unknown.
This paper describes the results of inflorescence and flower development studies using different histological and molecular cytological approaches. Nuclear integrity and cell division patterns in reproductive organs were investigated through DAPI staining and in situ hybridization using a histone H4 gene probe.
Key Results
The earliest sex-related difference in flower buds is observed at an otherwise ‘bisexual’ stage, at which the number of cells in the gynoecium of pistillate flowers is higher than in their staminate counterparts. In the pistillate flower, staminodes (sterile stamens) display precocious arrest of development followed by cell differentiation. In the staminate flower, pistillodes (sterile gynoecium) undergo some degree of differentiation and their development ceases shortly after the ovule has been initiated. Staminode and pistillode cells exhibit nuclear integrity although they did not show any accumulation of histone H4 gene transcripts.
These results strongly suggest that the developmental arrest of sterile sex organs and the subsequent unisexuality of date palm flowers result from a cessation of cell division and precocious cell differentiation rather than from cell death.
PMCID: PMC2908162  PMID: 20534596
Date palm; reproductive development; cell division patterns; sex determination

Results 1-4 (4)