乙烯与NO互作调控荷花耐镉性的机制研究

Nelumbo nucifera, a famous traditional flower with high ornamental and socio-cultural values in China, has removal efficiency of heavy metal, and thus could be used for water purification. Recent studies have revealed that both ethylene and nitric oxide (NO) play an important role in enhancing heavy metal tolerance through the regulation of antioxidant system in plants, but the interaction mechanisms between them have not been clarified. In this study, N. nucifera was taken as the material to investigate the mechanisms by which ethylene and NO interacted and affected antioxidant system under cadmium stress to enhance its cadmium tolerance by morphology, transcriptomics, physiological and molecular biology methods, based on the verification of their roles in regulating cadmium-stress responses in N. nucifera. Focus on the influences of exogenous ethylene and NO on the production of the other under cadmium stress, and the relationship between ethylene and NO in the regulation of antioxidant system under cadmium stress by exogenous ethylene with or without a NO scavenger treatment as well as exogenous NO with or without ethylene inhibitors treatment, ultimately illustrating the molecular mechanisms by which they cooperated in enhancing cadmium tolerance of N. nucifera. The results of this study will not only enrich the theory of N. nucifera cadmium tolerance, but also provide a scientific basis for its large-scale utilization for cadmium phytoremediation, and a theoretical basis for creating new cultivars with excellent resistance to cadmium by molecular breeding techniques.

荷花是我国的传统名花，具有很高的观赏价值和社会文化价值；研究证实荷花还具有较强的清除重金属的能力，可用于水体的净化。最近研究表明，乙烯和NO均能通过调节抗氧化系统进而增强植物对重金属的耐性，但二者在其中的互作机制尚不明确。本研究以荷花为试材，在验证乙烯、NO调节荷花响应镉胁迫作用的基础上，通过形态学、转录组学、生理生化及分子生物学等手段探查镉胁迫下乙烯与NO互作调控荷花抗氧化系统进而增强其耐镉性的机制。重点研究镉胁迫下外源乙烯或NO处理对另一方的影响，以及通过外源乙烯与NO清除剂单独或复合处理、外源NO与乙烯抑制剂单独或复合处理对抗氧化系统的作用，明确镉胁迫下乙烯与NO在调控抗氧化系统中的相互关系，最终解析二者互作调控荷花耐镉性的分子机理。本研究的预期结果可丰富和完善荷花耐镉性理论，为将其应用于镉污染水体的植物修复提供科学依据，同时也为利用分子育种手段创造优良耐镉品种奠定理论基础。

近年来，水体镉污染面积和程度不断增加，威胁植物生长及食品安全。莲花是我国传统名花，具有很高的观赏价值和社会文化价值；研究证实莲花还具有较强的清除重金属的能力，可用于重金属污染水体的净化。最近研究表明，乙烯和一氧化氮（NO）均能通过调节抗氧化系统进而影响植物对重金属的耐性，但二者在调控抗氧化系统中的相互关系尚不明确。本研究以‘微山湖红莲’为试材，通过形态学、转录组学、生理生化及分子生物学等手段首先探索了莲幼苗对镉胁迫的响应，以及乙烯、NO在其中的重要作用机制。结果表明：1）镉胁迫影响莲幼苗的生长，导致叶片失绿。镉胁迫下莲叶片中的大量差异表达基因涉及代谢途径、次级代谢合成、膜系统、苯丙素合成、谷胱甘肽代谢、植物激素信号转导等途径，暗示这些途径可能参与莲幼苗对镉胁迫的响应；2）乙烯主要或至少能够通过影响乙烯信号元件EIN2影响乙烯合成基因ACS、ACO的表达，增强内源乙烯释放量，调控抗氧化系统CAT、APX、GR活性及AsA、GSH含量的变化，从而改变活性氧积累，参与调控镉胁迫对莲幼苗生长的抑制及伤害；3）NO主要通过调控氧化系统GR、APX的活性及AsA、GSH含量的变化，进而影响活性氧积累及膜系统受损程度，参与莲幼苗对镉胁迫的响应。在上述基础上，本研究继续探索了镉胁迫下乙烯与NO互作调控莲花抗氧化系统进而影响其耐镉性的机制，发现外源施加NO专一性清除剂PTIO，能够逆转ACC的作用，同时外源添加乙烯作用抑制剂STS也能拮抗SNP的作用，因此，认为镉胁迫下，乙烯和NO存在交互作用，二者相互促进，共同调控AsA-GSH循环系统，进而影响莲幼苗的活性氧水平等， 参与调控镉胁迫对莲幼苗生长的抑制及伤害。研究结果丰富了莲花耐镉性理论，为将莲花应用于镉污染水体的植物修复提供科学依据，同时也为未来利用分子育种手段创造优良耐镉品种奠定理论基础。