壳聚糖诱导菜用大豆耐盐性的生理和分子机制研究

It is known that chitosan plays an important role in protecting biotic and abiotic stressed plants. Our previous work found that chitosan can reduce salt injury index of vegetable soybean seedlings, increase their net photosynthetic rate and dry weight. Accordingly, we believe that chitosan can improve photosynthetic efficiency of vegetable soybean, and then alleviate the injury caused by salt stress. But how the chitosan increases salinity tolerance of vegetable soybean through regulating its photosynthetic metabolism is unclear so far. By foliar application of chitosan, we will study the effects of chitosan on photosynthetic characteristics, xanthophyll cycle and heat dissipation, chloroplast antioxidant system, chlorophyll metabolism of two vegetable soybean cultivars with diferent salt tolerance under salt stress in order to make clear physiological mechanism of chitosan in protecting photosynthetic organ, promoting pigment metebolism, increasing photosynthetic efficiency, and then improving salt tolerance of vegetable soybean. Meanwhile, we will study the effects of chitosan on protein expression of vegetable soybean chloroplast and corresponding mRNA levels under salt stress, and then clarify physiological function of differential proteins and the correlation between the differential protein and mRNA levels so as to reveal molecular mechanism of vegetable soybean salt tolerance induced by chitosan. This study will provide theoretical basis for vegetable soybean adverse resistance cultivation depending application of chitosan, and for vegetable soybean genetic improvement and resistance breeding too. The differential proteins may also lay the foundation for molecular breeding for resistance.

壳聚糖对逆境胁迫植物有重要的保护作用。我们的前期工作发现，壳聚糖可降低菜用大豆幼苗的盐害指数、提高其净光合速率及干质量。据此，认为壳聚糖可提高菜用大豆的光合效率，缓解盐胁迫对其造成的伤害。但壳聚糖如何调控菜用大豆光合代谢，进而缓解盐胁迫危害目前尚不清楚。我们将通过叶面喷施壳聚糖溶液的方法，研究盐胁迫下壳聚糖对2个耐性不同的菜用大豆品种的光合特性，叶黄素循环及热耗散，叶绿体抗氧化系统，叶绿素代谢等的影响，明确盐胁迫下壳聚糖保护光合器官，促进色素代谢，提高光合效率，进而提高其耐盐性的生理机制；研究盐胁迫下壳聚糖对菜用大豆叶绿体蛋白质表达及差异蛋白mRNA丰度的影响，阐明差异表达蛋白的生理功能、差异蛋白表达与其mRNA丰度的相关性，揭示壳聚糖诱导菜用大豆耐盐性的分子机制。为外源增施壳聚糖进行菜用大豆抗逆栽培及菜用大豆的遗传改良和抗性育种提供理论依据，获得的差异蛋白质也可为抗性分子育种奠定基础。

摘要：采用蛭石栽培，以耐盐性不同的2个菜用大豆品种为试材，研究盐胁迫下壳聚糖对菜用大豆光合作用的生理和分子调节机制。结果表明：盐胁迫下，壳聚糖可调节气孔运动以提高胞间CO2浓度；通过抑制叶绿素酶活性从而缓解叶绿素含量的下降；通过促进电子传递，加速过剩光能耗散，通过促使AsA-GSH循环持久快速、有效运转，及时清除过量H2O2，以缓解光抑制及活性氧对光合器官的损伤，进而促进光合作用。iTRAQ叶绿体蛋白质组分析表明，盐胁迫下壳聚糖可诱导光能捕获、光电子传递、CO2同化、糖代谢、基因表达、蛋白质代谢、解毒、细胞壁修复等相关功能蛋白质差异表达。qRT-PCR分析发现，盐胁迫诱导上调蛋白“酸性磷酸酶样蛋白”与其基因表达水平一致，其余测试基因水平均与相应蛋白质表达水平不一致。说明蛋白质水平与mRNA丰度的相关性极小，壳聚糖对蛋白质表达的影响很可能是通过对转录后翻译过程的调节，或调节翻译后水平等实现的。本研究阐明了盐胁迫下壳聚糖促进菜用大豆光合作用的生理和分子调节机制，对增施外源物质提高植物抗盐性具有重要的理论价值，同时，获得的差异蛋白也可为抗性分子育种奠定基础。