Effects of methyl jasmonate and carotenogenic inhibitors on gene expression and carotenoid accumulation in coriander (Coriandrum sativum L.) foliage

Coriander (Coriandrum sativum L.), a commonly used annual herb that accumulates carotenoids upon methyl jasmonate (MeJA) treatment, provides an excellent model to investigate carotenogenesis and gene regulation. To explore key mechanisms involved in enhancing carotenoids, transcriptional expression profile of ten carotenogenic genes in the presence of MeJA and various gene specific inhibitors were investigated. Foliar application of MeJA (10 mu M) increased expression levels of CsPDS (phytoene desaturase), CsZDS (zeta-carotene desaturase), CsCHYE (carotene epsilon - hydroxylase) and CsLCYE (lycopene beta-cyclase) genes, and their transcript levels were strongly associated with carotenoid content, where, three days after treatment, 3.9 & 6.1 fold increase was observed for beta-carotene and lutein respectively. The regulatory effect of key genes, CsPDS, CsZDS, CsLCYE and LCYB were further confirmed by using gene-specific inhibitors fosmidomycin, norflurazon and amitrol. Norflurazon- the phytoene desaturation inhibitor leads to a decrease in beta-carotene and lutein content correlated with CsPDS, CsZDS gene induction. Our results clearly demonstrate that MeJA induced-signalling network evokes carotenogenic genes, leading to the accumulation of carotenoids. This knowledge may help to develop precise strategies for remodelling carotenoid pathway so that desired levels of a particular carotenoid in leafy vegetables is achievable.