用转录组学和蛋白质组学关联解析甘蔗蔗糖积累的分子调控机制

High-sucrose content is one of the major aims in sugarcane breeding. At present, new sugarcane varieties are primarily developed through cross breeding. However, conventional sexual hybridization requires long cycles to achieve variety improvement and the efficiency is very low, generally it takes 10–12 years to develop a new variety. Molecular breeding is the trend of modern breeding, and identification of new genes is the precondition of molecular breeding. Integrative transcriptomics and proteomics analysis, better than single analysis of them, was used to mine batches of new genes on more and more crops. Ethephon is highly effective in promoting sucrose accumulation and affecting several metabolism processes related to growth and sucrose accumulation in sugarcane. The present work would analyze the differentially expressed genes in sugarcane genotypes with different sucrose levels under ethephon induction condition by intergration of transcriptome and proteome data. The candidate genes associated with sucrose accumulation would be screened, and the biological functions of some novel genes would be dissected, to construct the regulatory network of candidate genes involved in sucrose accumulation, elucidate the molecular mechanisms regulating sucrose accumulation in sugarcane, and provide references for high sugar breeding by molecular methods.

高糖是甘蔗新品种选育的重要目标，然而甘蔗常规杂交育种周期长，工作量大，通常育成一个品种需要10-12年时间。分子育种是现代育种的方向，而新基因的发掘是作物分子育种的基础。转录组学和蛋白质组学关联分析由于优于单方面分析而被越来越多应用于作物批量基因发掘。乙烯利是甘蔗增糖的有效调控物质，影响甘蔗生长和糖分积累的多个代谢过程。本项目拟选择高、中、低糖甘蔗基因型，在糖分积累期通过乙烯利诱导和非诱导处理，分析各处理的转录组和蛋白质组，并通过关联分析筛选出参与甘蔗蔗糖积累的候选基因，然后验证关键基因的功能，初步构建甘蔗蔗糖积累相关基因间的调控网络，解析甘蔗蔗糖积累的分子调控机制，为甘蔗高糖分子育种奠定理论和技术基础。

甘蔗是我国主要的糖料作物，甘蔗糖占我国食糖总产量的90%左右。高糖是甘蔗新品种选育的重要目标。由于甘蔗遗传背景复杂且遗传基础窄，通过常规育种提高甘蔗糖分的进度非常缓慢。通过分子辅助育种可能是甘蔗糖分获得突破的关键途径。解析甘蔗蔗糖积累的调控机理，挖掘调控高糖的关键基因，对甘蔗高糖分子辅助育种具有重要意义。乙烯利是蔗糖积累的重要调控物质。本项目首先分析了高、中、低糖三个甘蔗基因型乙烯利处理前后的转录组和蛋白质组。转录组测序分析鉴定出约16万个基因，其中8.6万个基因被注释为与碳水化合物代谢、信号传导、定位、转运、水解、生长、催化活性、膜和贮藏相关。在所有基因型和处理组合中约有25000个基因差异表达。基因型比乙烯处理对差异基因表达有显著影响。在低糖基因型中，蔗糖和淀粉代谢基因对乙烯处理更敏感。乙烯利引起许多应激相关转录因子、糖代谢、激素代谢和表观遗传修饰相关基因表达差异。乙烯诱导的乙烯应答转录因子、细胞质酸性转化酶和细胞壁结合转化酶、以及ATP酶在低糖基因型中的表达显著高于高糖基因型，表明乙烯利刺激库活性增加并促进低糖基因型中蔗糖的积累。通过蛋白质组学分析，也鉴定了一批受乙烯诱导并与甘蔗糖分积累相关的重要蛋白，为进一步研究甘蔗糖分积累奠定了基础。综合关联分析转录组和蛋白质组学数据表明，蔗糖积累的主要限制因子是源叶中蔗糖的合成和到库组织中蔗糖的运输，当受乙烯利诱导后，ERFs调控SPSs和SUSs的表达增加蔗糖合成，而ATP酶，转化酶 (主要为CWINV3) 和蔗糖转运蛋白SUTs促进蔗糖的运输，从而提高蔗糖的含量。本项目初步绘制出甘蔗蔗糖积累相关基因分子调控网络，部分揭示了甘蔗蔗糖积累的分子调控机制。