Abstract

Proline is an important osmotic regulatory substance that can rapidly accumulate in plants under drought stress. A key gene in the proline biosynthesis pathway is P5CR , which responds to abiotic stresses and hormones. When the VyP5CR gene cloned from extremely drought-resistant Chinese wild grape Vitis yeshanensis accession 'Yanshan-1′ is overexpressed in Arabidopsis thaliana , drought tolerance improves. In this study, the effect of VyP5CR on drought resistance was examined in transgenic grapevine, and its upstream regulatory factors were determined. The results showed that when VyP5CR was overexpressed in V. vinifera cultivar 'Thompson Seedless', transgenic vines were more drought-tolerant than the wild type under drought stress, with much less wilting and significantly smaller stomatal apertures and lower transpiration rate. Malondialdehyde content, electrolyte leakage, and H 2 O 2 and O 2 − accumulations were lower, but the contents of chlorophyll and proline, the net photosynthetic rate and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were higher. The expression of drought stress-related genes was also significantly up-regulated in transgenic plants. Thus, VyP5CR increased drought tolerance of transgenic grapevine. Yeast one-hybrid and luciferase activity assays indicated that MADS-box transcription factors VyAGL42 and VyMADS23 directly bound to the VyP5CR gene promoter and activated its transcription. Therefore, VyAGL42 and VyMADS23 might synergistically regulate drought tolerance of grapes with VyP5CR .