丛枝菌根化田菁耐盐的生理和分子机制研究

Sesbania (Sesbania cannabina Pers.) belongs to the family leguminosae, with strong salt and barren resistance. It has been widely used as a green manure for saline soil improvement in Yellow River Delta area. Previous studies showed that salt tolerance of arbuscular mycorrhizal sesbania plant was significantly enhanced, and the host has also undergone some significant changes in physiological and biochemical characteristics. This project is planned for selecting a salt-tolerance symbiotic system formed by Sesbania cannabina Pers. plants and suitable arbuscular mycorrhizal fungus; constructing differentially expressed EST library of salt-stressed arbuscular mycorrhizal S.cannabina plants by suppression subtractive hybridization (SSH) technique, screening potential salt-tolerance symbiotic EST after sequencing and analysis; analysis temporal and spatial expression pattern of the salt-tolerance symbiotic sequences by real-time PCR; establishing salt tolerance expression profiles of arbuscular mycorrhizal S.cannabina symbiosis association, and screening and cloning genes that play important role in salt-tolerance of arbuscular mycorrhizal-S.cannabina symbiosis in full-length to elaborate the mechanism of salt tolerance on transcriptional perspective. At last, combing study on photosynthetic physiology of arbuscular mycorrhizal-S.cannabina under salt stress to provide new scientific theories for understanding the physiological and molecular mechanism of AM fungi enhancing S.cannabina’s salt-tolerance.

田菁 (Sesbania cannabina Pers.)具有较强的耐盐、耐瘠能力，在黄河三角洲地区被广泛用做降盐绿肥作物。前期研究表明，丛枝菌根（AM）化田菁的耐盐性明显增强，且宿主在生理生化特性上也发生明显改变。本项目拟选择一种AM真菌，与田菁形成耐盐共生体，采用抑制消减杂交（SSH）技术构建菌根化田菁在盐胁迫下差异表达的EST（Expressed Sequence Tag）文库，经序列测序、分析后，筛选潜在的共生抗盐EST；再结合real-time PCR分析菌根化田菁耐盐序列的时空表达, 分析后建立菌根化田菁耐盐相关基因的表达谱，从转录水平上阐述接种AM真菌后田菁耐盐性提高的分子机制，并筛选、克隆在共生体耐盐中起重要作用基因的全长序列。最后，结合对菌根化田菁在盐胁迫下光合生理表现的分析，为深入探索AM真菌提高宿主植物耐盐性的生理和分子机制提供新的科学依据。

田菁适应性强，是优良豆科绿肥作物，可用作盐土生物修复。在已经验证田菁–AM共生体具有良好耐盐能力的基础上，进一步探究菌根化田菁的内部机理。在生理机制层面，通过药理学及生化生理学手段检测发现可能参与调控菌根化田菁耐盐的信号分子，如独脚金内酯（SLs）、脱落酸（ABA）等，受盐胁迫诱导产生，在共生条件下有效缓解植株的盐胁迫症状，保护田菁植株光合机构，增加生物量。在分子机制层面，通过转录组高通量测序得到菌根化田菁的盐胁迫差异表达谱。通过对上述差异表达谱进行加权基因共表达分析以及共表达基因—性状相关性分析，发现大量涉及调控菌根化田菁耐盐过程的转录因子。通过荧光定量PCR证明，其中一些MYB基因序列在受到盐胁迫处理后的菌根化田菁幼苗中特异性表达或较非菌根植株显著增强。据此，对其中一条在共生胁迫条件下表达量最高的MYB基因序列进行全长克隆，命名为ScMYB1。这部分成果将为今后深入了解菌根化植物的获得性耐盐机制奠定基础。