Identification of white campion (<it>Silene latifolia</it>) guaiacol <it>O</it>-methyltransferase involved in the biosynthesis of veratrole, a key volatile for pollinator attraction

• Main Authors: Gupta Alok K, Akhtar Tariq A, Widmer Alex, Pichersky Eran, Schiestl Florian P
• Format: Article
• Language: English
• Published: BMC 2012-08-01
• Series: BMC Plant Biology
• Subjects: Floral scent; VOC; 1, 2-dimethoxybenzene; Pollination; <it>Hadena bicruris</it>
• Online Access: http://www.biomedcentral.com/1471-2229/12/158

<p>Abstract</p> <p>Background</p> <p><it>Silene latifolia</it> and its pollinator, the noctuid moth <it>Hadena bicruris,</it> 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 <it>S. latifolia</it>, the molecular basis of scent biosynthesis in this species has not yet been investigated.</p> <p>Results</p> <p>We isolated two full-length cDNAs from <it>S. latifolia</it> that show similarity to rose orcinol <it>O</it>-methyltransferase. Biochemical analysis showed that both <it>S. latifolia guaiacol O-methyltransferase1</it> (<it>SlGOMT1</it>) &<it>S. latifolia guaiacol O-methyltransferase2</it> (<it>SlGOMT2</it>) encode proteins that catalyze the methylation of guaiacol to form veratrole. A large K_m 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 <it>SlGOMT</it> genes are specifically expressed in flowers and male <it>S. latifolia</it> flowers had 3- to 4-folds higher level of <it>GOMT</it> gene transcripts than female flower tissues. Two related cDNAs, <it>S. dioica O-methyltransferase1</it> (<it>SdOMT1</it>) and <it>S. dioica O-methyltransferase2</it> (<it>SdOMT2</it>), were also obtained from the sister species <it>Silene dioica</it>, 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 <it>SlGOMT1</it> and <it>SlGOMT2</it> genes evolved under positive selection, whereas <it>SdOMT1</it> and <it>SdOMT2</it> genes show no evidence for selection.</p> <p>Conclusions</p> <p>Altogether, we report the identification and functional characterization of the gene, <it>SlGOMT1</it> that efficiently catalyzes veratrole formation, whereas another copy of this gene with only one amino acid difference, <it>SlGOMT2</it> was found to be less efficient for veratrole synthesis in <it>S. latifolia</it>.</p>