亚精胺调控甜玉米淀粉代谢参与种子活力形成的分子机理研究

Poor seed quality is a serious impediment to the development of the sweet corn industry. Seed vigor is an important indicator of seed quality and is closely related with the field emergence. Seed vigor is gradually formed during seed development, and will reach the highest value when seed is physiological maturity. However, the molecular mechanism of seed vigor formation is still a scientific problem to be solved. Some studies showed that seed vigor could be influenced by starch metablism, in addition, there is relatively close relationship between spermidine and seed vigor. Our preliminary studies also confirmed that spermidine played a significant role in the regulation of seed vigor formation and involved in seed starch metabolism during seed development of sweet corn. However, up to now, there is no systematic report on the molecular mechanisms of spermidine regulating starch metablism and seed vigor formation of sweet corn. Therefore, based on the results of our preliminary extensive researches, the new RNA sequencing technology was used in present study to find the key genes involved in spermidine regulation on seed vigor especially on seed strach metablism of sweet corn. Using the genetic transformation technology to study the gene function and regulation networks. The findings will clarify the molecular mechanism of involving seed vigor formation of sweet corn through the spermidine regulation of starch metabolism during seed development, and has important theoretical significance and applied potential for seed quality improvement of sweet corn.

种子质量低下严重阻碍了甜玉米产业的发展。种子活力是种子质量的重要指标，与种子田间出苗密切相关。种子活力随着种子发育逐渐形成，至生理成熟时达到最高，但种子活力形成的分子机理尚是亟待解决的科学难题。已有研究表明种子中淀粉代谢影响种子活力，而亚精胺（Spd）与种子活力尤其种子干重的关系密切。本课题组前期研究结果也证实Spd参与调控甜玉米发育期间种子活力的形成，且参与种子淀粉的合成代谢，但至今尚未见有关Spd调控甜玉米淀粉代谢及种子活力形成分子机理的系统研究报道。因此，本研究拟采用转录组测序技术，通过对mRNA与miRNA的分析鉴定，挖掘Spd参与调控甜玉米种子发育期间淀粉合成代谢的关键基因，应用遗传转化技术，研究基因功能及调控网络。通过Spd对淀粉合成代谢的调控，揭示Spd参与甜玉米种子活力的分子机理，结果具有重要的理论意义和应用潜力，将为提高甜玉米种子质量和品质改良开拓新的方向。

种子活力是种子质量的重要指标，与种子田间出苗密切相关。但种子活力形成的分子机理尚是亟待解决的科学难题。本项目研究了外源Spd及其抑制剂CHA处理对甜玉米种子发育和种子活力的影响，表明外源Spd处理可显著提高籽粒淀粉含量，提高甜玉米种子活力，促进幼苗生长，并对种子体积增大和鲜重积累有促进作用。通过转录组和miRNA测序分析，筛选出Spd调控甜玉米种子发育的差异表达基因，并挖掘到参与Spd调控甜玉米淀粉代谢的关键候选基因ZmTPP2及被靶向调控的miR319。初步探讨了Spd 促进甜玉米种子发育早期ZmTPP2转录水平的调控机理。发现Spd可能通过提高miR319的表达量，抑制ZmTPP2的表达，显著提高种子发育期间淀粉含量尤其是支链淀粉含量，促进种子干物质的积累，提高种子活力。通过遗传转化技术研究了拟南芥同源基因tppg突变株系的种子发育情况以及对Spd的响应，发现tppg突变体植株较矮，种子活力较野生型WT明显降低，Spd可一定程度上恢复突变体相关性状，表明TPP在 Spd 调控种子发育及活力形成中起重要作用。本项目研究结果对提高种子活力具有重要的理论意义和应用潜力，将为提高甜玉米种子质量和品质改良开拓新的方向。

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