甜瓜Golden2-Like转录因子调节叶绿体发育的分子机理研究

Chloroplasts are the photosynthetic organelle in plants, and the product of photosynthesis is the material basis for crop yield and quality. Recent studies have revealed that Golden2-Like (GLK) transcription factors play important roles in chloroplast development, which can also improve fruit quality and flavor by regulating the development of fruit chloroplast. However, the molecular mechanism of GLK transcription factors in regulating chloroplast development and its regulatory networks are still not clear and remain elusive. Our research group has identified a yellow-green leaf accession in our melon germplasm collection, and the chlorophyll content and the number of chloroplasts were significantly decreased in this accession which resulted in the reduced photosynthetic efficiency and fruit quality. The yellow-green leaf phenotype was controlled by a single recession gene (named ygl), we have cloned this gene using a map-based cloning strategy，and it encoded a GLK transcription factor. In this project, we will explore the function of CmGLK gene in regulating chloroplast development and fruit quality by developing near iso-genic lines (NILs) and genetic transformation. In addition, we will combine RNA-Seq, ChIP-Seq and yeast two-hybrid to reveal the molecular mechanism and regulation network of CmGLK gene in regulating chloroplast development. The results will not only enrich the molecular mechanism of GLK transcription factor in regulating chloroplast development in higher plants, but also provide new insight for the genetic improvement of fruit quality in melon.

叶绿体是植物进行光合作用的关键场所，而光合作用产物是作物产量和品质形成的物质基础。研究发现Golden2-Lik（GLK）转录因子在叶绿体发育中起着非常重要的作用，它可通过调节果实叶绿体的发育来提高果实的品质和风味。然而，GLK转录因子调节叶绿体发育的作用机理与调控网络尚不清楚，仍有待深入研究。课题组前期发现一个甜瓜叶色黄绿材料，其叶绿素含量、叶绿体数目、光合效率及果实品质均显著降低。我们已经图位克隆到控制该黄绿叶色性状的基因（ygl），它编码一个GLK转录因子。本项目将通过遗传转化和构建cmglk基因的近等基因系，解析该基因在甜瓜叶绿体发育中的功能及其对果实品质的影响，同时通过RNA-Seq、ChIP-Seq和酵母双杂交等手段揭示CmGLK基因调节甜瓜叶绿体发育的分子机理与调控网络。研究结果不仅能丰富和完善GLK转录因子调节叶绿体形成的分子机制，也将为甜瓜果实品质改良提供新的思路和方向。

叶绿体是绿色植物进行光合作用的重要细胞器，相关基因的突变可能会引起叶绿体发育缺陷，导致叶绿素含量降低与光合作用减弱，从而产生各种叶色突变表型，而这个过程常伴随着作物产量和品质的下降。解析叶绿体发育的调控网络，对提高植物光合效率、提升果实品质有重要的研究意义。目前在甜瓜中已经发现了几个控制叶色的基因，但都没有被克隆，其作用机理也不清楚。课题组前期通过图位克隆技术，成功鉴定出一个控制甜瓜黄绿叶色性状的基因CmGLK。在此基础上，本研究通过亚细胞定位、表达分析、叶绿素含量测定及结构观察等研究，证实了CmGLK基因在叶绿体发育和叶绿素合成中的关键作用。通过异源转化拟南芥和番茄以及构建甜瓜近等基因系等方法，验证了CmGLK基因通过影响植物叶片叶绿体发育从而对果实品质产生影响，为甜瓜品质育种提供了新思路。转录组测序结果显示，CmGLK基因显著影响着几个叶绿体发育关键基因的表达；进一步利用RNA-seq、酵母杂交、双分子荧光互补等技术，获得了与CmGLK互作的蛋白，初步解析了CmGLK基因调节甜瓜叶绿体发育的遗传调控网络和分子机理，为进一步深入研究CmGLK基因对甜瓜果实品质影响的分子机制奠定了坚实的基础。