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Logo of bmcpsBioMed Centralsearchsubmit a manuscriptregisterthis articleBMC Plant Biology
 
BMC Plant Biol. 2012; 12: 158.
Published online Aug 31, 2012. doi:  10.1186/1471-2229-12-158
PMCID: PMC3492160
Identification of white campion (Silene latifolia) guaiacol O-methyltransferase involved in the biosynthesis of veratrole, a key volatile for pollinator attraction
Alok K Gupta,corresponding author1,2 Tariq A Akhtar,3 Alex Widmer,2 Eran Pichersky,3 and Florian P Schiestl1
1Institute of Systematic Botany, University of Zurich, Zurich, CH-8008, Switzerland
2ETH Zurich, Institute of Integrative Biology, Plant Ecological Genetics, Zurich, CH-8092, Switzerland
3Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
corresponding authorCorresponding author.
Alok K Gupta: alok.gupta/at/systbot.uzh.ch; Tariq A Akhtar: taakhtar/at/umich.edu; Alex Widmer: alex.widmer/at/env.ethz.ch; Eran Pichersky: lelx/at/umich.edu; Florian P Schiestl: florian.schiestl/at/systbot.uzh.ch
Received April 24, 2012; Accepted August 27, 2012.
Abstract
Background
Silene latifolia and its pollinator, the noctuid moth Hadena bicruris, represent an open nursery pollination system wherein floral volatiles, especially veratrole (1, 2-dimethoxybenzene), lilac aldehydes, and phenylacetaldehyde are of key importance for floral signaling. Despite the important role of floral scent in ensuring reproductive success in S. latifolia, the molecular basis of scent biosynthesis in this species has not yet been investigated.
Results
We isolated two full-length cDNAs from S. latifolia that show similarity to rose orcinol O-methyltransferase. Biochemical analysis showed that both S. latifolia guaiacol O-methyltransferase1 (SlGOMT1) &S. latifolia guaiacol O-methyltransferase2 (SlGOMT2) encode proteins that catalyze the methylation of guaiacol to form veratrole. A large Km value difference between SlGOMT1 (~10 μM) and SlGOMT2 (~501 μM) resulted that SlGOMT1 is 31-fold more catalytically efficient than SlGOMT2. qRT-PCR expression analysis showed that the SlGOMT genes are specifically expressed in flowers and male S. latifolia flowers had 3- to 4-folds higher level of GOMT gene transcripts than female flower tissues. Two related cDNAs, S. dioica O-methyltransferase1 (SdOMT1) and S. dioica O-methyltransferase2 (SdOMT2), were also obtained from the sister species Silene dioica, but the proteins they encode did not methylate guaiacol, consistent with the lack of veratrole emission in the flowers of this species. Our evolutionary analysis uncovered that SlGOMT1 and SlGOMT2 genes evolved under positive selection, whereas SdOMT1 and SdOMT2 genes show no evidence for selection.
Conclusions
Altogether, we report the identification and functional characterization of the gene, SlGOMT1 that efficiently catalyzes veratrole formation, whereas another copy of this gene with only one amino acid difference, SlGOMT2 was found to be less efficient for veratrole synthesis in S. latifolia.
Keywords: Floral scent, VOC, 1, 2-dimethoxybenzene, Pollination, Hadena bicruris
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