干旱和盐胁迫下硅诱导番茄可溶性糖积累的机理和作用

Silicon can increase drought and salt tolerance of plants. However, the mechanisms still remain unclear. We find that silicon can enhance the accumulation of soluble sugar in tomato plants under drought and salt stresses. Given the roles of soluble sugar in stress tolerance of plants, it is speculated that the accumulated soluble sugar play important roles in the tolerance of tomato plants to drought and salt stresses. However, the mechanisms and roles of silicon-induced soluble sugar accumulation are still unclear. In this project, the following research will be conducted: (a) clarifying the mechanisms for silicon-induced soluble sugar accumulation in tomato plants under drought and salt stress by analyzing the soluble sugar components, and activity changes of rate-limiting enzymes and their gene expressions in soluble sugar metabolism and transport; and determining the key enzyme and its gene responsible for silicon-induced soluble sugar accumulation; (b) verifying the function of the key gene responsible for soluble sugar accumulation and the regulative role of silicon in soluble sugar accumulation by using over-expression and RNA interference transgenic plants of the key gene; (c) using the above transgenic plants and the wild type as materials, analyzing the contribution of soluble sugar in silicon-induced changes in osmotic potential of plants, clarifying the relationship between soluble sugar accumulation and stress hormone ABA and ethylene, and clarifying the role of soluble sugar in oxidative stress tolerance. Through implementing this project, the mechanisms and roles of silicon-induced soluble sugar accumulation in tomato plants under drought and salt stress will be clarified, which will help to elucidate the mechanisms for silicon-induced drought and salt tolerance in tomato plants. This research will also provide a theoretical basis for silicon application in tomato production.

硅可提高植物的抗旱抗盐性，但其作用机制仍不清楚。我们发现，硅可促进干旱和盐胁迫下番茄可溶性糖的积累。鉴于可溶性糖在植物抗逆中的作用，推测它的积累在硅诱导番茄抗旱抗盐中起着重要的作用。但目前对硅诱导可溶性糖积累的机理和作用还不清楚。本项目拟分析干旱和盐胁迫下番茄可溶性糖组分及其代谢与转运中关键节点酶活性和基因表达的变化，阐明硅诱导番茄可溶性糖积累的机制、确定可溶性糖积累的关键酶及相关基因；克隆可溶性糖积累的关键酶基因，构建其过表达和RNA干扰转化体系、获得转基因植株，验证其在可溶性糖积累中的作用与硅的调控；以转基因植株及野生型为试材，分析可溶性糖在硅对渗透势调控中的贡献、阐明可溶性糖积累与逆境激素ABA和乙烯之间的关系、明确可溶性糖在抗氧化中的作用。通过该研究，阐明干旱和盐胁迫下硅诱导番茄可溶性糖积累的机理和作用，从而阐明硅提高番茄抗旱抗盐性的机制，为硅肥在番茄生产中的应用提供理论根据。

营养学途径是改善番茄等蔬菜作物抗旱抗盐性的重要方法。施硅能提高植物的抗旱抗盐性，但机理仍不清楚。本项目探讨了可溶性糖积累在硅诱导植物抗旱抗盐性中的作用及调控。结果表明，在模拟干旱和盐胁迫下，加硅可促进番茄的光合速率、促进根系水分吸收、降低植株的氧化损伤，从而有利于光合产物的积累、促进植株生长。加硅提高了干旱下番茄叶片果糖和葡萄糖含量。对可溶性糖的代谢分析表明，硅处理可促进干旱下糖的运转，从而增强对胁迫植株的能量供应、提高其抗旱性。盐胁迫也显著增加了植株中葡萄糖、果糖和蔗糖的含量。硅对盐胁迫下可溶性糖积累的调控与基因型有关。硅处理抑制了光合反馈抑制、提高了盐胁迫下蔗糖的利用率、有利于蔗糖向淀粉的转换。加硅促进了光合产物向根内的运输，从而提高植物抗逆性。在番茄中，SUS3和SUT4在其各自家族中表达量较高，暗示其在蔗糖运输中起着重要作用。通过农杆菌侵染子叶法进行遗传转化，获得了SUS3的RNAi植株和SUT4过表达植株。番茄SUS3表达被抑制后果糖和葡萄糖含量均升高。与野生型相比，番茄SUS3沉默株系果实中与种子发育相关的基因SlMAC、SlFUS3和SlABI3表达明显下调，表明SUS3可能参与了种子的发育。在正常供水条件下，过表达SUT4促进了番茄植株地上部的生长、改变了根型；过表达植株根系构型的变化可能与葡萄糖介导的糖信号和激素水平变化有关。过表达SUT4降低了番茄植株的抗旱性，可能通过影响番茄不同部位的葡萄糖含量而促进己糖激酶的表达，进而促进ABA合成，参与干旱胁迫响应。结果表明，SUT4可能在调控番茄生长和干旱胁迫响应中起着重要的作用。加硅促进的可溶性糖的积累可能起着渗透调节剂的作用、对保证水分胁迫下根系的水分吸收起着重要的作用、从而提高植物的抗逆性。本研究将为今后进一步阐明硅抗逆的分子机制、抗逆相关基因的克隆和功能研究奠定了基础。