葡萄糖-6-磷酸脱氢酶在青稞抗旱中的调节作用及分子机理的研究

Apart from glycolysis, pentose phosphate pathway is the other main degradation pathway of glucose, and is the main source of NADPH in the cellular biosynthesis. Studies indicate that it is widely involved in the regulation of growth and development in plants as well as in the tolerance to environmental stresses. Glucose-6-phosphate dehydrogenase (G6PDH) is one of the key regulatory enzymes in pentose phosphate pathway. Our previous research showed that G6PDH plays a role in the tolerance to salt and heat stresses in plants, and is involved in H2O2 and NO accumulation under salt stress. .Highland barley is the irreplaceable foodstuff for Tibetan, and is also the main raw material for its feed processing and brewing industry. However, to date, studies on the functional gene, the gene-expression characteristics of G6PDH as well as its regulatory mechanism of stress adaptability in highland barley are nearly blank. In this project, we will carry out researches in this regard using different varieties of highland barley with different stress resistance. The research contents include: cloning the functional gene of G6PDH in highland barley; investigating the gene expression characteristics and the regulatory mechanism of G6PDH isoenzyme; analyzing the mechanism for how G6PDH participate in the response of highland barley to drought stress; investigating the relationship between the G6PDH activity and signaling molecules (NO, H2O2, cGMP) as well as the signal regulatory mechanism. The pioneer systematical studies on the action and regulatory mechanism of pentose phosphate pathway in highland barley will lead to elucidating the mechanism of highland barley tolerance to environmental stresses, and provides the theoretical guidance for molecular breeding programs of highland barley.

戊糖磷酸途径是除糖酵解外葡萄糖的另一主要降解途径，是细胞内生物合成所需还原力NADPH的主要来源。研究表明戊糖磷酸途径广泛参与了植物生长发育调节和环境胁迫耐受。葡萄糖-6-磷酸脱氢酶（G6PDH）是其限速酶之一。我们的研究表明G6PDH参与了植物对盐及热胁迫的耐受；介导了盐胁迫诱导的H2O2与NO累积。.青稞是藏民不可替代的主粮，也是其饲料加工和酿造业的原料。目前关于青稞G6PDH功能基因、基因表达模式及在逆境下调节机理的研究仍是空白。本项目拟以不同抗性青稞品种为材，克隆G6PDH功能基因，研究其表达模式与调控机理；解析G6PDH如何参与青稞对干旱胁迫的应答并阐述其机制；探讨G6PDH与信号分子NO、H2O2、cGMP在青稞抗旱中的关系及信号调节机制。这是首次系统地探讨戊糖磷酸途径在青稞逆境适应性中的作用与调节机理，该研究有助于阐释青稞适应高原环境的抗逆机制，可为其分子遗传育种提供理论依据

植物呼吸代谢多样性是其对多变环境的适应性表现。戊糖磷酸途径是除糖酵解外葡萄糖的另一降解途径，该途径广泛参与了植物生长发育调节和对逆境的响应；抗氰交替途径，呼吸链上的能量耗散途径，也与植物的抗逆性有关。青稞属青藏高原最具特色的农作物，是藏民不可替代的主粮。本项目以抗性不同的青稞品种为实验材料，探讨了磷酸戊糖途径、交替途径在青稞耐受环境胁迫（干旱、盐、紫外、低氮）中的作用与调节机制，并克隆了青稞磷酸戊糖途径限速酶G6PDH基因家族基因G6PDH4、G6PDH5。主要研究结果显示：a. 磷酸戊糖途径和交替途径协同参与青稞对盐、UV-B辐射的交叉适应。磷酸戊糖途径关键酶G6PDH和交替途径末端氧化酶AOX之间在蛋白表达及翻译后水平存在相互调节、相互依赖的机制；两者共同参与了稳定青稞叶片氧化还原状态，进而维持了正常的光合特性与气孔运动。b. 利用RACE技术克隆了青稞G6PDH4、G6PDH6基因，蛋白序列分析发现G6PDH4定位于质体，G6PDH6定位于胞质，且两个基因的蛋白序列在进化中具有高度的保守性，青稞和大麦中G6PDH4蛋白的同源性为95.34%，G6PDH6蛋白的同源性为99.61%。c. 交替途径参与了青稞对低氮胁迫的耐受。低氮胁迫导致叶绿体中还原力的大量积累，进而会通过梅勒反应产生活性氧，导致光抑制发生，降低光合效率。此时，苹果酸穿梭机制会被激活，其限速酶NADP-MDH活性显著增加，该途径可将叶绿体中过剩的还原力转移到线粒体中通过交替途径耗散，进而维持了青稞叶片的光合能力。这是首次系统地探讨戊糖磷酸途径、交替途径在青稞逆境适应性中的作用与调节机理，该研究有助于阐释青稞适应高原环境的抗逆机制，可为其分子遗传育种提供理论依据。