ABA和BR调控植物重金属耐受性的分子机制研究

The contamination of heavy metals has been becoming a severe environmental issue worldwide. The exceeded heavy metals in soils resulted directly from heavy metal pollution has been seriously threatening the health of human. With the advantages of higher feasible, environment friendly, and cost effectively, phytoremediation have been utilizing to study and remediate the soil heavy metal contamination. Currently, the key technology that limits the practical application of phytoremediation is to enhance the tolerance of plants to heavy metals and to improve the agronomic traits of heavy metal hyperaccumulators for suitable planting. Many studies have revealed the physiological and biochemical mechanisms during growth and development of plant in response to heavy metal stress. However, the molecular mechanism in which the regulation of gene function and gene expression profile specifically respond to heavy metal stress remains to be further elucidated. Therefore, in this study, the RNA-Seq and qRT-PCR technologies will be used to explore the influence of Cd exposure on the global gene expression profile of mung bean seedlings, further revealing the molecular mechanism of plant in response to heavy metal stress. Furthermore, the influence of ABA and BRs, which are two important plant growth regulators, on the global gene expression profile of mung bean seedlings will be detected to unravel the molecular mechanism in which ABA and BRs regulate the growth and development of plants. Finally, on the basis of the above two results, we will investigate the influences of ABA and BRs on the global gene expression profiles of mung bean seedlings under Cd stress, and illuminate the molecular mechanisms by which ABA and BRs regulate the tolerance of plants to heavy metal stress. The results obtaining from this study will be of significant for further highlighting the theoretical basis of plant tolerance to heavy metals, and exploring the new genes that are specifically involved in the plant tolerance to heavy metals. Consequently, this study would provide the theoretical support and new technical idea for phytoremediation of heavy metal contamination in soils.

重金属污染土壤植物修复技术的关键在于提高植物的重金属耐受性。研究表明，植物生长调节物能显著提高植物的重金属耐受性。但至今关于调控这一过程的分子机制，还缺乏系统深入地研究。本项目拟以绿豆为材料，以污染最严重的镉(Cd)为胁迫，运用RNA-Seq和qRT-PCR技术，在全基因水平研究Cd对绿豆幼苗基因功能谱和基因表达谱的影响，探讨植物响应重金属胁迫的分子机制；以脱落酸(ABA)和油菜素内酯(BRs)为代表，研究其对绿豆幼苗基因功能谱和基因表达谱的影响，揭示ABA和BRs调控植物生理过程的分子机制；在上述两项结果的基础上，研究Cd胁迫下，ABA和BRs对绿豆幼苗基因功能谱和基因表达谱的影响，阐明ABA和BRs调控植物重金属耐受性的分子机制。研究结果将丰富植物重金属耐受性理论，发掘新的植物抗重金属基因资源，为重金属污染土壤的植物修复技术提供理论支撑和技术新思路。

土壤重金属污染造成了严重的环境问题。植物能够吸收并在体内积累重金属离子，过量的重金属离子导致植物生长减缓，产量下降。植物生长调节物，如ABA和BR等能够减缓重金属离子对植物的毒害作用，提高植物的重金属耐受性，但其机制，特别是分子机制，以及重金属响应基因等，有待揭示。基于此，本项目以绿豆幼苗为研究材料，运用形态学、生理学、生物化学、转录组学和生物信息学等方法，开展了ABA和BR调控绿豆镉(Cd)耐受性的生理生化及分子机制研究。我们的研究表明，外源ABA和BR(以活性异构物eBL为例)都能缓解Cd对绿豆幼苗的胁迫和毒性。在生理生化层面上，二者能够完全或部分恢复因Cd而升高的抗氧化酶活性、抗氧化剂水平和丙二醛水平。其调控机制具有相似性，即维护细胞抗氧化系统的动态平衡，保护细胞膜脂过氧化，提高胁迫下细胞的活力，从而提高植物对Cd的耐受性。在分子层面上，外源ABA和BR都能够降低Cd胁迫显著改变的基因的表达水平，即Cd胁迫显著上调/下调的基因，在施加ABA和BR后被显著下调/上调，说明ABA和BR能够恢复Cd改变的基因的表达水平。这些基因涉及多样性的功能和代谢过程，而胁迫响应相关基因和信号转导相关基因及通路起重要作用。在理论上，我们的研究为植物生长调节物调控植物重金属耐受性的机制提供了重要的科学资料。在实践上，我们的研究提示，外源ABA和BR可用于降低植物对土壤中重金属的吸收和积累，提高植物对重金属的耐受性，可用于植物修复重金属污染土壤和安全农产品的生产。该项研究获得的绿豆ABA、BR和Cd响应基因，为今后的研究提供了重要依据。项目按计划执行，执行情况好，超额完成了计划书目标任务，取得了较好的研究成果，发表标注第一资助的中英文论文10篇，培养了博士生1名，硕士生3名。