小麦籽粒特异转录因子TaMYB44对胚乳淀粉品质影响的研究

Common wheat (Triticum aestivum L.) is an important cereal crop worldwide. Starch synthesis in the endosperm is largely influencing starch quality and kernel weight. Co-expression analysis is an effective way to identify transcription factors regulating genes involved in starch synthesis pathway. A transcription factor, TaMYB44, is highly expressed in the developing seeds of thirty-three cultivars detected from transcriptome data, and its expression is highly corresponding with many enzyme genes involved in starch synthesis pathway, such as TaSUS1, TaAGP, TaGBSSI and TaSSI. This suggests TaMYB44 may be an upstream regulator of these key enzyme genes. The program aims to study the biological function of TaMYB44, and to validate its influence during seed developing and starch synthesis through transgenic experiments. This program also aims to detect favored variant alleles in wheat germplasm populations, which may provide theoretical basis for starch quality improvement and yield increase in the wheat breeding.

小麦（Triticum aestivum L.）是重要的粮食作物。小麦籽粒中的淀粉合成是影响品质及粒重的重要因素。共表达分析是解析淀粉合成通路基因调控因子的有效途径。通过大规模小麦籽粒转录组研究发现，转录因子基因TaMYB44在33个小麦籽粒转录组数据中均呈现出高水平表达，且与淀粉合成关键酶基因如TaSUS1、TaAGP、TaGBSSI、TaSSI等的表达呈高度正相关，推测可能是其中重要酶基因的上游调控基因。本项目拟通过分子生物学手段研究TaMYB44的生物学功能，通过转基因实验验证TaMYB44对籽粒发育和淀粉合成的影响，以及在小麦自然群体中挖掘其优异等位变异类型，为改良淀粉品质及提高小麦产量提供理论依据。

本研究通过小麦花后籽粒转录组共表达网络分析，筛选到影响籽粒淀粉合成的胚乳特异表达的转录因子TaMYB44和TaNAC020。TaMYB44是转录抑制因子，在水稻中超表达后千粒重降低、淀粉及直链淀粉含量降低、蛋白质含量提高；在小麦中超表达后千粒重显著降低，编辑后千粒重显著提高；TaMYB44能够抑制淀粉合成通路的TaSUS2和TaSPS启动子活性。小麦中存在MYB44-WD40-bHLH95复合体，该基因可能以复合体方式参与下游基因的调控。TaMYB44负调控过氧化物酶基因TaPOD，说明TaMYB44可能参与细胞程序化死亡。TaNAC020同样调控粒重及淀粉合成。TaNAC020在水稻中超表达后千粒重及淀粉含量提高、直链淀粉含量降低。TaMYB44-4A、TaNAC020-A和TaNAC020-B的单倍型与千粒重显著相关，优异单倍型在育种过程中均受到了正向选择。本项目的研究结果说明用共表达分析结合多组学数据进行重要农艺性状的调控研究是可行的，TaMYB44和TaNAC020开发的分子标记均可以用于小麦育种改良。