拟南芥D53-like SMXLs调控植物盐耐受性的机制研究

Soil salinization is a major limiting factor in agricultural production. It is a significant research subject to explore salt-tolerant genes, analyze the molecular mechanism and improve the tolerance of plant to stress. A new phytohormone, stirgolactone, plays an important role in plant response to stress by MAX2 protein. Recently, our studies showed that SMXL6/7/8 mutants were sensitive to salt stress as a MAX2 repressor in SLs signal transduction, and no relevant reports on SMXLs family members involved in salt tolerance in plant have been seen. In the present project, the salt stress sensitivity of Arabidopsis D53-like SMXLs family mutants such as smxl6/7/8 will be analyzed, the temporal and spatial expression patterns of SMXL6/7/8 under salt stress, the treatment of SLs and ABA conditions will be studied using physio-biochemical, cellular and molecular techniques, and the functional redundancy of SMXLs family genes in salt stress response also will be explored; the function of SMXL6/7/8 in salt and SLs signals cross-taking will be revealed, the functional relationship and signal network of SMXL6/7/8 with SLs, ion homeostasis and ABA, and the salt-tolerant function of D53-like SMXLs family genes and its molecular mechanism will be uncovered finally, which will provide a new way and idea for molecular mechanism of plant salt tolerance. This project has not only the important scientific significance, but also the potential application in improving the salt tolerance of plants.

土壤盐渍化是影响农业生产的重要限制因素，因而发掘高效耐盐基因并解析其分子机制是当前植物抗逆研究的重点。新型激素独脚金内酯（SLs）通过MAX2在植物抗逆中发挥重要功能。最近我们发现：SMXL6/7/8作为SLs信号转导中MAX2的抑制子，其突变体对盐胁迫非常敏感，但目前尚无SMXL6/7/8参与植物耐盐的报道。本项目拟以拟南芥D53-like SMXLs突变体为材料，通过生理生化、细胞及分子生物学等方法，阐明SMXL6/7/8在盐胁迫、SLs和ABA处理后的时空表达模式；探索SMXLs家族基因在盐胁迫应答中的功能冗余性；揭示SMXL6/7/8在盐信号与SLs信号交联中的功能；解析SMXL6/7/8与SLs、离子稳态及ABA之间的功能关系及信号网络，旨在揭示D53-like SMXLs家族基因的耐盐功能及分子机理，为揭示植物耐盐分子机制提供新途径和新思路，具有重要的理论意义和潜在的应用价值。

盐旱胁迫作为重要的非生物胁迫严重影响着农业生产的各个方面。发掘植物新的抗盐旱胁迫基因并解析其功能对推动植物耐盐旱分子机制的研究具有重要的科学意义和应用价值。独脚金内酯（strigolactones，SLs）作为一种新型的植物激素，参与调节植物发育的各个方面。最近的研究表明，独脚金内酯在植物抗病和盐旱胁迫中也发挥重要的作用。本项目通过形态学比较、遗传杂交、生理生化、转录组学以及分子生物学等方法，研究了拟南芥独脚金内酯信号通路的抑制子SUPPRESSOR OF MORE ALLIARY GROWTH2-LIKE6（SMXL6）、SMXL7和SMXL8在盐旱胁迫应答中的功能，为揭示独脚金内酯信号转导与盐旱胁迫之间的信号交联提供了重要信息。项目主要研究成果如下：1）smxl6/7/8三突变体叶表皮细胞的长宽比增大、细胞面积减小且单位面积的细胞数目增多，表明D53-like SMXLs 参与调控叶片形态的发育；2）D53-like SMXLs参与调节盐胁迫条件下的种子萌发、幼苗生长和盐诱导的成熟植株叶片的衰老，而外源独脚金内酯加剧了smxl6/7/8三突变体盐胁迫敏感的衰老表型；3）转录组分析揭示SMXL6、7、8介导的独脚金内酯信号通过调控激素介导的生长发育、糖代谢以及叶片衰老等过程参与盐胁迫响应；4）SMXL6、7、8蛋白通过直接抑制衰老相关基因NAP和SAG113的转录活性参与调控盐胁迫诱导的衰老过程；5）D53-like SMXLs通过调节ABA诱导的气孔关闭、花青素的积累、角质层的厚度以及胁迫相关基因的表达负向调节植物的干旱耐受性。综上，D53-like SMXLs 通过多种方式负向调控植物盐胁迫诱导的衰老和植物的干旱耐受性。本研究不仅具有重要的学术价值，同时还为未来提高农作物盐旱胁迫耐受能力提供了新的思路。