cl7.1调控水稻耐淹萌发机制的研究

In recent years, direct seeding rice has been developed continuously because of saving labor and time. However, rice germination rate is thought to be the crucial limiting factor of popularizing direct seeding rice. Water direct-seeding is favorable to control weed but adverse to seedling emergence of direct seeding rice. Coleoptile length can directly represent the ability of submergence tolerance during germination in rice. At present, our understanding of submergence tolerance during germination in rice is extremely limited. In our former research, a major gene cl7.1 responsible for coleoptile length was identified. It encodes a heat shock protein. So far, there is no report about the gene. Based on the gene, a series of objectives are planned to be achieved in this project: (1) confirming the target gene using functional complementation and over expression, and revealing its expression characteristics. (2) revealing the regulation relationship between the gene and ABA during germination under submergence. (3) uncovering the corresponding features of the target gene enhancing submergence tolerance during germination through physiological analysis. (4) illuminating its role in the expression and regulation network involving in submergence tolerance during germination through RNA-seq. It is to elucidate the regulatory pathway and mechanism of the target gene involving in submergence tolerance during germination, based on multi-aspect studies. This project will broaden our understanding about the mechanism of submergence tolerance during germination in rice. It will also offer an important reference for developing direct seeding rice.

直播稻因省工省力近年来得以不断增长，出苗率问题已严重制约直播稻的发展。水直播有利于控制杂草但不利于直播稻出苗。胚芽鞘的长度可直接反应水稻的耐淹萌发能力，目前对水稻耐淹萌发的了解十分有限。我们先期的研究发现一个控制胚芽鞘长度的主效基因cl7.1，是一个热激蛋白基因，迄今尚未见该基因的相关报道。本项目以该基因为研究目标，①通过功能互补、过表达等验证目的基因的功能，并阐明其表达特性；②阐明该基因在淹水萌发时与ABA的调控关系；③通过生理学分析，揭示其促进耐淹萌发的应对特征；④通过转录组分析明确其在耐淹萌发表达调控网路中的参与作用，探讨目的基因参与耐淹萌发的调控途径及机制。通过项目的研究，可拓宽对水稻耐淹萌发机制的认识，并为直播稻品种的培育提供重要的参考。

直播稻因省工省力近年来得以不断增长，出苗率问题已严重制约直播稻的发展。水直播有利于控制杂草但不利于直播稻出苗。胚芽鞘的长度可直接反应水稻的耐淹萌发能力，目前对水稻耐淹萌发的了解十分有限。本项目对先前发现的一个控制胚芽鞘长度的主效基因cl7.1开展功能验证与表达特征分析、在淹水萌发中与ABA的调控关系、生理及细胞学方面的分析以及转录组分析等主要研究内容。主要结果如下：通过Cas9技术在中花11中敲除目的基因CL7.1能使淹水萌发时的胚芽鞘伸长，基因CL7.1受低氧胁迫诱导表达，淹水萌发时在胚芽鞘的胚中轴明显表达，其组织特异性表达可能与其调控胚芽鞘的伸长有关。敲除系中内源ABA逐渐累积，其ABA合成相关基因大部分上调，多数ABA信号传导相关基因也上调，可解析敲除系对ABA更敏感的缘由。敲除系在淹水萌发12 h大部分淀粉酶相关基因表达量显著上调、淀粉酶活力也相对较高，基因Adh1和PDC1的表达均显著上调，CAT和SOD活力于淹水12 h后均得到提高、MDA含量随淹水时间延长不断下降，生理指标上的变化使敲除系更有利于抵抗淹水胁迫，从而促进胚芽鞘伸长。转录组分析揭示DEGs主要富集在氧化还原反应、胁迫响应、细胞扩张和分化、糖酵解/糖异生等过程，蔗糖和淀粉代谢、谷胱甘肽代谢、植物激素信号转导等途径，qPCR验证到敲除系中大部分扩展蛋白相关基因表达水平明显上升，有利于其胚芽鞘的伸长。本研究验证了目的基因cl7.1调控水稻淹水萌发的功能，初步揭示了其调控淹水萌发的生理及分子机制—淹水萌发时目的基因导致ABA的积累，应对淹水胁迫的一些关键基因上调表达、主要生理指标得以改善，有利于胚芽鞘伸长的相关基因被激活，最终导致胚芽鞘的伸长。研究结果具有一定的新颖性，在理论层面上有助于丰富我们对水稻耐淹萌发机制的科学认识，对指导水稻育种也具备一定的参考价值。