Tan Yanxiao, Li Mingjun, Yang Yingli, Sun Xun, Wang Na, Liang Bowen, Ma Fengwang
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University Yangling, China.
Front Plant Sci. 2017 Jan 24;8:33. doi: 10.3389/fpls.2017.00033. eCollection 2017.
Phytocystatins (PhyCys) comprise a group of inhibitors for cysteine proteinases in plants. They play a wide range of important roles in regulating endogenous processes and protecting plants against various environmental stresses, but the underlying mechanisms remain largely unknown. Here, we detailed the biological functions of , a member of cystatin genes isolated from . This gene was activated under water deficit, heat (40°C), exogenous abscisic acid (ABA), or methyl viologen (MV) (Tan et al., 2014a). At cellular level, MpCYS4 protein was found to be localized in the nucleus, cytoplasm, and plasma membrane of onion epidermal cells. Recombinant MpCYS4 cystatin expressed in was purified and it exhibited cysteine protease inhibitor activity. Transgenic overexpression of in () and apple () led to ABA hypersensitivity and series of ABA-associated phenotypes, such as enhanced ABA-induced stomatal closing, altered expression of many ABA/stress-responsive genes, and enhanced drought tolerance. Taken together, our results demonstrate that is involved in ABA-mediated stress signal transduction and confers drought tolerance at least in part by enhancing stomatal closure and up-regulating the transcriptional levels of ABA- and drought-related genes. These findings provide new insights into the molecular mechanisms by which phytocystatins influence plant growth, development, and tolerance to stress.
植物半胱氨酸蛋白酶抑制剂（PhyCys）是植物中一类半胱氨酸蛋白酶抑制剂。它们在调节内源过程和保护植物免受各种环境胁迫方面发挥着广泛而重要的作用，但其潜在机制仍 largely unknown。在这里，我们详细阐述了从 中分离出的半胱氨酸蛋白酶抑制剂基因家族成员 的生物学功能。该基因在水分亏缺、高温（40°C）、外源脱落酸（ABA）或甲基紫精（MV）处理下被激活（Tan等人，2014a）。在细胞水平上，发现MpCYS4蛋白定位于洋葱表皮细胞的细胞核、细胞质和质膜。在 中表达的重组MpCYS4半胱氨酸蛋白酶抑制剂被纯化，并且它表现出半胱氨酸蛋白酶抑制剂活性。 在 （）和苹果（）中的转基因过表达导致ABA超敏反应和一系列与ABA相关的表型，例如增强的ABA诱导的气孔关闭、许多ABA/胁迫响应基因的表达改变以及耐旱性增强。综上所述，我们的结果表明 参与ABA介导的胁迫信号转导，并且至少部分地通过增强气孔关闭和上调ABA和干旱相关基因的转录水平来赋予耐旱性。这些发现为植物半胱氨酸蛋白酶抑制剂影响植物生长、发育和胁迫耐受性的分子机制提供了新的见解。
