FATTY ACID METABOLISM IN LEAVES AND ROOTS ASSOCIATED WITH IMPROVED DROUGHT TOLERANCE IN AGROSTIS STOLONIFERA EXPRESSING SAG12-IPT GENE CONTROLLING CYTOKININ SYNTHESIS

摘要

Creeping bentgrass over-expressing the SAG12-ipt gene encoding adenine isopentenyl phosphotransferase controlling cytokinin synthesis exhibited improved drought tolerance.This study was designed to elucidate whether changes in membrane fatty acid composition and saturation levels in leaves and roots are associated with improved growth of creeping bentgrass (Agrostis stolonifera) under drought stress.SAG12-ipt transgenic and wild-type (WT) plants were exposed to well-watered conditions or drought stress for 15 d.Leaves and roots were sampled at 8 d and 15 d of drought and the following morphological and metabolic parameters were compared between the transgenic and WT plants,including visual evaluation of turf quality (TQ),relative water content of leaves (RWC),photochemical efficiency of leaves (Fv/Fm),leaf and root membrane stability via electrolyte leakage (EL),leaf and root lipid peroxidation by quantifying malondialdehyde production (MDA),leaf and root membrane fatty acid content and saturation level.Compared to WT plants,transgenic plants maintained significantly higher TQ,higher leaf RWC and Fv/Fm,as well as lower EL and MDA in leaves and roots under drought stress.Transgenic plants maintained higher levels of long-chain unsaturated fatty acids such as linoleic (C18:2) and linolenic (C18:3) acid during drought compared to WT plants.Increased unsaturated fatty acids could help maintain membrane fluidity,contributing to continued leaf and root growth during drought stress in the transgenic plants as demonstrated by enhanced turf quality and physiological activities.