番茄转录因子SlbHLH061和SlbHLH152调控铁稳态的分子机制

Iron (Fe) is an indispensable micronutrient for plant growth and development. Identifying the key components of iron signaling pathway and further elucidating their functions will contribute to the increasement of crop iron content and the cultivation of iron-rich crops. In a previous study, SlbHLH068 has been characterized as an important Fe deficiency responses gene in tomato. To identify transcription factors functioning upstream of SlbHLH068, yeast one-hybrid screening was performed using the promoter of SlbHLH068 as bait. From the screening, we obtained two transcription factors with unknown functions, SlbHLH061 and SlbHLH152, which bind and activate the promoter of SlbHLH068. SlbHLH061 physically interacted with SlbHLH152, and SlbHLH061 positively regulated Fe deficiency responses in tomato. In this study, we will further clarify the functions of SlbHLH061 and SlbHLH152 in regulating Fe homeostasis. Meanwhile, we will analyze the regulation of SlbHLH061 and SlbHLH152 to SlbHLH68 by genetic complementation experiment. Moreover, we will confirm the interaction between SlbHLH061 and SlbHLH152, and investigate whether the protein complex of SlbHLH061 and SlbHLH152 affect the transcriptional function or DNA-binding activity of SlbHLH061 and SlbHLH152. Finally, we will illustrate the molecular mechanism of SlbHLH061 and SlbHLH152 regulating Fe homeostasis in tomato. These results will further enrich the iron signaling network in tomato, and contribute to the molecular breeding of iron-rich tomato.

铁是植物生长发育所必需的微量元素。挖掘铁信号途径的关键调控基因并阐明其功能对于作物铁含量的提高及富铁作物新品种的培育具有重要意义。项目前期以番茄铁稳态关键调控基因SlbHLH068的启动子为诱饵进行了酵母单杂交实验，筛选获得了两个功能未知的转录因子SlbHLH061和SlbHLH152。研究发现，SlbHLH061和SlbHLH152可以结合并激活SlbHLH068的启动子，且二者可以互作形成蛋白复合物，SlbHLH061正调控番茄铁稳态。在前期基础上，本项目拟系统研究SlbHLH061和SlbHLH152调控番茄铁稳态的生物学功能，明确二者的蛋白相互作用并分析二者及其蛋白复合物对靶基因SlbHLH068的调控效应，最终阐明SlbHLH061和SlbHLH152调控番茄铁稳态的分子机制。研究结果有望进一步丰富番茄铁信号网络，同时为富铁番茄新品种的培育提供基因资源和理论依据。

番茄是我国主要的蔬菜作物之一，铁是番茄生长发育所必需的微量元素。挖掘番茄铁信号途径的关键调控基因并阐明其功能对于番茄铁含量的提高及富铁番茄新品种的培育具有重要意义。本项目以番茄铁稳态关键调控基因SlbHLH068的启动子为诱饵进行了酵母单杂交实验，筛选获得了两个功能未知的转录因子SlbHLH061和SlbHLH152。SlbHLH152和SlbHLH061在根、茎、叶、花和果实中均表达，且二者的表达均不受缺铁诱导。slbhlh152突变体对缺铁敏感，叶绿素含量、铁还原酶活性和铁含量均显著降低，缺铁相关基因的表达均下调。相反，SlbHLH152的过表达植株对缺铁耐受，叶绿素含量和铁含量显著升高，缺铁相关基因的表达均上调。slbhlh061突变体也对缺铁敏感，SlbHLH061的过表达植株铁含量显著升高。因此SlbHLH152和SlbHLH061都是正调控番茄铁稳态的。SlbHLH152和SlbHLH061可以在酵母细胞中相互作用，且SlbHLH152和SlbHLH061均能激活SlbHLH068的启动子。以上结果说明SlbHLH152和SlbHLH061均通过介导SlbHLH068的转录来正调控番茄铁稳态。研究结果能够为阐明番茄铁稳态调控网络奠定理论基础，同时为富铁番茄新品种的培育提供新的基因资源。