Abstract
9-cis-epoxycarotenoid dioxygenase (NCED) is a key enzyme involved in the biosynthesis of abscisic acid (ABA), which is associated with drought tolerance in plants. An osmotic-inducible VaNCED1 gene was isolated from a drought-resistant cultivar of Vitis amurensis and constitutively overexpressed in a drought-sensitive cultivar of Vitis vinifera. Transgenic plants showed significantly improved drought tolerance, including a higher growth rate and better drought resistant under drought conditions, compared to those of wild-type (WT) plants. After water was withheld for 50 days, the upper leaves of transgenic plants remained green, whereas most leaves of WT plants turned yellow and fell. Besides the increase in ABA content, overexpression of VaNCED1 induced the production of jasmonic acid (JA) and accumulation of JA biosynthesis-related genes, including allene oxide cyclase (AOC) and 12-oxophytodienoate reductase (OPR3). Moreover, transgenic plants possessed advantageous physiological indices, including lower leaf stomatal density, lower photosynthesis rate, and lower accumulation of proline and superoxide dismutase (SOD), compared to those of WT plants, indicating increased resistance to drought stress. Quantitative real time polymerase chain reaction (RT-qPCR) analysis revealed that overexpression of VaNCED1 enhanced the expression of drought-responsive genes, such as ABA-responsive element 1 (ABRE1), ABRE binding factors 2 (ABF2), plasma membrane intrinsic proteins 2 (PIP2), C-repeat/DRE-Binding Factor 4 (VvCBF4) and ABA-insensitive 5 (ABI5). Although the development of transgenic plants was delayed by 4 months than WT plants, because of seed dormancy and abnormal seedlings, the surviving transgenic plants provided a solid method for protection of woody plants from drought stress.
Highlights
Water is essential for plant growth; it carries nutrients to support plant growth and serves as a medium for in vivo reactions
Wilting was not observed in ZSY subjected to 10% PEG6000 treatment, whereas Thompson Seedless’ (TS) showed wilting after 4 h, followed by superoxide dismutase (SOD) Activity Assay
The expression level of VvABI5 was drastically induced by drought stress, the increasing fold is 139.86 (WT), 473.81 (CVAN4) and 20.94 (CVAN5). These results showed that VaNCED1 gene could greatly improve drought tolerance in plants
Summary
Water is essential for plant growth; it carries nutrients to support plant growth and serves as a medium for in vivo reactions. Climate change in recent years has accelerated the expansion of drylands, threatening the growth, yield, and quality of plants because of drought stress. Faced with the challenge of climate and environmental changes, breeders need to add new traits to improve tolerance to abiotic stresses (Chapman et al, 2012). Abscisic acid (ABA) is an important plant hormone involved in various physiological processes in plants, such as the response to abiotic stresses (Seo and Koshiba, 2002; Fujita et al, 2011; Awan et al, 2017). When plants are subjected to abiotic stress, ABA rapidly accumulates, inducing stomatal closure to reduce water loss via transpiration (Zhang et al, 2008; Estrada-Melo et al, 2015)
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