Ecophysiological response to water stress and regulation of gene expression for a 9-cis-epoxycarotenoid dioxygenase in Vitis vinifera L. 'Italia'

Abscisic acid (ABA) is associated with regulating plant adaptive responses to various environmental stresses. In particular, drought stress signals are transmitted through at least two pathways: one is abscisic acid (ABA)-dependent, and the other is ABA-independent. In the first case, drought stress increases the cellular ABA levels, which induces the expression of drought stress-responsive genes, such as 9-cis-epoxycarotenoid dioxygenase (NCED) and zeaxanthin epoxidase (ZEP). These genes belong to the carotenoid biosynthesis scenario. To date, most research of grapevines has focused on the physiological mechanisms of ABA during fruit ripening. Our interest is on studying the role of NCED and ZEP genes as candidate genes exhibiting up-regulation upon drought-stressed conditions. At the same time, several plant physiological parameters, such as leaf water status (Ψ1), net assimilation rate (A), stomatal conductance (gs), transpiration rate (E), and soil water potential (Ψs), were monitored. To explain the complex molecular pattern undergoing these physiological changes, we investigated the levels of expression of one candidate gene encoding for VvNCED1. The results provided evidence of a different transcriptional pattern of the gene between the control and stressed plants, leading to a major accumulation of NCED1 transcripts in the stressed plants.