游离氨基酸在蓖麻耐抗和累积镉中的作用及代谢调控

Free amino acids represent the major compounds in the nitrogen metabolism of plants and play an important role in the regulation of growth and development, response to heavy metal stress and enrichment of heavy metals. Ricinus Communis L. is an ideal plant for the bioremediation of cadmium polluted soil, due to its tolerance for cadmium combined with a high accumulation potential. However, to date the role of free amino acids with respect to the tolerance and the accumulation of cadmium in Ricinus Communis L. is not clear. Therefore, according to the previous studies, Zibo-3 (low-Cd accumulator) and Zibo-9 (high-Cd accumulator) will been chosen for pot experiments investigating the changes of free amino acids in Ricinus Communis L. after being exposed to various gradient of cadmium stress through simulating cadmium pollution in laboratory. Combined with nitrogen isotope composition of free amino acids and nitrogen metabolism indexes, the synthesis and metabolism of amino acids will be discussed. After the identification of the key amino acids regarding the cadmium tolerance, hydroponic experiment will be carried out to explore the effect and mechanism of exogenous amino acids on the enrichment of heavy metals in Ricinus Communis L. by the analysis of subcellular distribution and chemical form of Cd. This study will analyze the role of free amino acids in the resistance and adaption of Ricinus Communis L. to heavy metal stress. The results will provide new insights into the tolerance mechanisms for heavy metals in Ricinus Communis L., and will be helpful in promoting the adaption of plants to heavy metals by means of changing the endogenous amino acids content through transgene. Consequently, the data will provide scientific support to the phytoremediation in controlling heavy metal pollution.

游离氨基酸是植物体内氮素代谢的中心物质，在调节植物生长发育、抵抗重金属胁迫和积累重金属中起重要作用。蓖麻作为理想的镉污染修复植物，目前关于游离氨基酸在蓖麻耐抗和累积镉中的作用及功能还不清楚。本项目在前期研究基础上，以2种不同镉富集能力的蓖麻品种为材料，采用盆栽试验，设置不同浓度的镉胁迫处理，研究蓖麻不同组织中游离氨基酸对镉胁迫的响应特征，并筛选敏感的氨基酸种类；结合游离氨基酸氮同位素特征和氮代谢相关指标，分析氨基酸的合成代谢途径，初步探讨游离氨基酸在蓖麻解毒和累积镉中的作用；采用水培方法，通过在镉胁迫条件下添加外源敏感氨基酸，分析蓖麻的生长生理指标及其体内镉的化学形态及亚细胞分布特征，以期进一步揭示游离氨基酸在蓖麻抵御镉毒害和调节镉吸收中的作用机理。本项目的研究将有助于深入认识植物重金属耐性机理，为将来通过转基因手段改变植物内源氨基酸代谢，增强植物的重金属耐性和富集能力提供科学依据。

重金属胁迫会干扰植物代谢过程，并危害植物的生长发育。碳氮稳定同位素和游离氨基酸的组成可以反映植物对环境胁迫的反应，可作为植物生理适应过程的指标。蓖麻作为理想的镉污染修复植物，关于蓖麻耐受和富集镉的机制已开展诸多研究，而关于游离氨基酸在蓖麻耐抗和累积镉中的作用及还不清楚，植物碳氮同位素与植物重金属胁迫的关系鲜有研究。本项目以2个蓖麻品种为研究材料，采用盆栽和水培试验，设置不同浓度的镉胁迫处理，研究蓖麻不同组织中游离氨基酸对镉胁迫的响应特征，结合碳氮同位素特征(δ13C和δ15N)，分析氨基酸的合成代谢途径，初步探讨游离氨基酸在蓖麻解毒和累积镉中的作用；采用水培方法，通过在镉胁迫条件下添加外源敏感氨基酸，分析蓖麻对镉的富集特征和生长生理指标，为利用氨基酸调控植物吸收重金属中的作用提供指导。研究结果表明：1）蓖麻中主要氨基酸包括Asp、Asn、Glu、Gln等，不同浓度及不同种类的重金属对游离氨基酸含量影响各异；2）与Zibo-3相比，Zibo-9对镉胁迫具有更强的耐受和富集能力，Zibo-9中Asp和Glu含量在总游离氨基酸含量的占比显著高于Zibo-3，且在镉胁迫时Arg的大量分泌，表明这3种氨基酸在Zibo-9解毒和富集镉中发挥重要作用；3）Gly、Glu和His的外源添加，有助于蓖麻对镉的吸收，并减缓对镉胁迫的伤害；4）蓖麻叶中的δ13C和δ15N值与镉胁迫呈正相关，δ13C和δ15N可作为植物响应重金属胁迫的生物监测指标。