调控SlGH3.4响应菌根共生信号的转录因子筛选和功能鉴定

菌根是自然界普遍存在的一种的互惠共生关系，可促进宿主对土壤中养分的吸收。研究表明，菌根共生的建立受到生长素信号调控，但目前生长素信号和菌根信号互作的分子机制并不清楚。前期我们从番茄菌根中鉴定到一个同时响应生长素信号和菌根共生信号的GH3家族基因，SlGH3.4。SlGH3.4在菌根中被特异性诱导，且表达受到启动子中两个顺式作用元件MYCS1和MYCS2调控。为了研究SlGH3.4响应菌根共生的调控机制，本项目将利用酵母单杂交系统从番茄菌根cDNA文库中筛选与MYCS1和MYCS2元件互作的转录因子，同时构建候选转录因子的超表达和突变体转基因材料对其进行功能验证。此外，本研究还将通过转录组测序，分析野生型、超表达以及突变体植株菌根中与生长素信号和菌根共生信号相关基因的表达变化。通过开展这些研究，本项目将阐明SlGH3.4响应和调控菌根共生的分子机理。

Arbuscular mycorrhizal (AM) symbiosis, formed by soil fungi belonging to Glomeromycotina and the roots of most land plants, is the most widespread mutualistic association in nature, and can faciltate plants to take up nutrients from soil. It has been documented that auxin signaling is involved in the regulation of AM symbiosis, however, the mechanisms underlying the interaction between auxin and mycorrhizal signalings have not been well deciphered. In our previous study, we found that an auxin-responsive GH3 gene, SlGH3.4, was strongly induced upon the formation of AM symbiosis. In mycorrhizal roots, SlGH3.4 was specifically expressed in the arbuscule-containing cortical cells, and its mycorrhiza-induced expression nature was regulated by two cis-acting elements, MYCS1 and MYCS2, in its promoter. In this study, to dissect the mechanisms underlying the auxin-mediated AM symbiosis, the yeast one hybirdization system will be employed to screen the transcription factors that can bind to the two cis-elements and regulate the AM-incued expression of SlGH3.4. We will also generate the mutants and overexpression lines for the candidate transcrition factor to dissect its potential roles in regulating AM symbiosis and auxin signaling. Additionally, we will perform RNA-seq transcriptom analysis to detect the transcription alterations of the genes involved in both auxin and mycorrhizal signalings between WT and transgenic plants. Accomplishing these studies, it will allow us to elucidate the molecular mechanisms underlying the response regulation and physiological roles of SlGH3.4 during the establishment of AM symbiosis.