BACKGROUND:HD-Zip genes encode several large and highly conserved protein families of transcription factors that play important roles in plant development and responses to environmental stress. To date, information about the involvement of HD-Zip in grape to drought response is limited. OBJECTIVE:The production of grapes is limited by a range of biotic and abiotic stresses, which cause significant losses in yield every year as well as a reduction in fruit quality. Identification and analysis of stress related genes in grapes are very important for cultivating more robust varieties with environmental stress resistance METHODS:We isolated a homeodomain-leucine zipper gene (HD-Zip), VvHDZ4, from grape, Vitis vinifera L. “Yatomi Rose”, and characterized VvHDZ4 based on analyses of its expression patterns, subcellular localization, transcription activity, and overexpression. RESULTS:We found that VvHDZ4 was highly expressed in roots and leaves, localized to nucleus, and activated the expression of reporter genes in yeast. The overexpression (OE) of VvHDZ4 led to enhanced drought stress tolerance in Solanum lycopersicum L. “Ailsa Craig” (tomato). The drought-tolerant phenotypes of the OE lines exhibited decreases in electrolyte leakage and rate of water loss, higher photosynthetic production and net photosynthesis rate, and showed up-regulation of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), all of which are key antioxidant enzymes known to be activated during drought stress. Moreover, we observed the up-regulation of four additional drought stress indicator genes, SIDREB2A, SIAREB, SIRD29 and SIERD10, in the OE lines. VvHDZ4 improved drought tolerance in tomato, and the modes of action possibly consist of reducing membrane damage, increasing photosynthetic productivity, and modulating the expression of stress defense genes. CONCLUSIONS:This work increases our understanding of the important roles HD-Zip transcription factors in the responses of plants to the environment, especially abiotic stress.

中文翻译：

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葡萄（Vitis vinifera L.）中的HD-Zip转录因子VvHDZ4赋予转基因番茄更高的抗旱性

背景：HD-Zip基因编码几个大的且高度保守的转录因子蛋白家族，这些家族在植物发育和对环境胁迫的响应中起着重要作用。迄今为止，关于HD-Zip参与葡萄抗旱的信息有限。目的：葡萄的生产受到一系列生物和非生物胁迫的限制，这会导致每年的产量大幅下降以及水果品质下降。葡萄中与胁迫相关的基因的鉴定和分析对于培育具有环境抗逆性的更强壮的品种非常重要。方法：我们从葡萄Vitis vinifera L分离了一个同源域-亮氨酸拉链基因（HD-Zip）VvHDZ4。“ Yatomi Rose”并基于其表达模式，亚细胞定位，转录活性和过度表达。结果：我们发现VvHDZ4在根和叶中高表达，定位于细胞核，并激活酵母中报道基因的表达。VvHDZ4的过表达（OE）导致茄子茄（Ailsa Craig）（番茄）的干旱胁迫耐受性增强。OE系的耐旱表型表现出电解质泄漏和水分流失率降低，光合产量和净光合速​​率提高，并表现出超氧化物歧化酶（SOD），过氧化氢酶（CAT），过氧化物酶（POD）上调，和抗坏血酸过氧化物酶（APX），所有这些都是已知的关键抗氧化酶，在干旱胁迫下会被激活。此外，我们在OE系中观察到另外四个干旱胁迫指示基因SIDREB2A，SIAREB，SIRD29和SIERD10的上调。VvHDZ4改善了番茄的耐旱性，其作用方式可能包括减少膜损伤，提高光合生产力和调节胁迫防御基因的表达。结论：这项工作增加了我们对HD-Zip转录因子在植物对环境特别是非生物胁迫的响应中的重要作用的理解。