Regulation of terpene production in methyl jasmonate treated cell-cultures

Abstract

Terpenes are responsible for flavors and aromas of grapes, however, they also protect from radiation, participate in biotic stress and antioxidant mechanisms. The phytohormone methyl jasmonate (MeJA) mediates many of these stress responses and has been associated with increased terpene content in berries. Here, we generated transcriptomic data of Vitis vinifera cv. ‘Gamay’ cells treated with MeJA (100 μM) and cyclodextrins (50 μM) to understand these responses. Ontology analysis revealed that up-regulated genes (URGs) were enriched in jasmonic acid biosynthesis and signaling terms, as expected. Inspection of transcription factors (TFs) among URGs allowed us to study uncharacterized TFs.  MapMan enrichment analysis on their TOP420 co-expressed genes (CEGs) allowed us to delimit some TFs highly enriched in jasmonate-related terms. This was the case of VviMYC2, the only grape member of the bHLH IIIe subgroup, and the best candidate for studying the regulation of jasmonate signaling. We confirmed the binding potential of MYC2 by DAP-seq, and combining it to the list of MeJA-URGs and MYC2-CEGs, we generated a list of high-confidence targets that included jasmonate-related genes and TFs such as MYB24, previously found to interact with MYC2 and required for the activation of terpenoid genes. In concordance, our MeJA data showed 13 significantly induced TPS genes, 9 of which are bound by MYB24, MYC2 or both. A few terpenoid compounds associated with the induced TPSs were significantly accumulated by MeJA. Our data suggests MYC2 regulates the jasmonate pathway and mediates terpene production cooperating with MYB24 in response to MeJA.