LAUSR

Polyacetylene (PA) compounds from Bidens pilosa are known to have several pharmacological activities. In this study, we aimed to elucidate the major genes encoding enzymes involved in the biosynthesis of PA in B. pilosa. Seven PA metabolites present in B. pilosa leaves were found to be induced by methyl jasmonate (MeJA) treatment and physical wounding. The transcriptomes of control, wounded and MeJA-treated leaves were obtained by high-throughput sequencing which resulted in 39,202 annotated gene fragment sequences. Comparative functional genomics using a DNA microarray established by the 39,202 annotated genes was used to profile the gene expression in B. pilosa leaf and root tissues. As no PA compounds were found in roots, the gene expression pattern in root tissue was used as a negative control. By subtracting MeJA-induced genes in roots, we obtained 1,216 genes annotated by a Gene Ontology search which showed an approximate 3-fold increase in leaves at days 1, 3 and 7 post-MeJA treatment. The expression levels of nine gene encoding enzymes with desaturation function were selected for confirmation by qRT-PCR. Among them, two genes, BPTC030748 and BPTC012564, were predicted to encode Δ12-oleate desaturase (OD) and Δ12-fatty acid acetylenase (FAA), respectively, based on protein primary sequence alignment. In B. pilosa leaf, RNAi knockdown of either gene concomitantly and significantly decreased PA content, while virus-mediated transient overexpression of either gene elevated the PA levels in comparison with the control-infected leaves. In summary, both OD and FAA likely play a role in the PA biosynthesis in B. pilosa plants.