植物响应镉胁迫的生理与分子机制研究进展

Advances in physiological and molecular mechanism of plant response to cadmium stress

重金属污染日益严峻,以镉(Cd)最为严重。镉是植物非必需元素,能够导致植物营养缺陷、光合作用强度降低、氧化应激等;轻则抑制植物生长,重则导致植物死亡。植物体内没有专一的镉转运蛋白,镉通常竞争性地借助锌、铁、钙等二价金属离子的转运体进入植物的各器官和组织。植物经过长期的演化,形成了一套应对镉胁迫的复杂机制:土壤中的镉进入植物根系后,根系细胞壁果胶的羧基自由基(-COO-)能够与Cd2+发生静电结合,阻碍部分镉进入原生质;部分进入原生质的镉一方面在植物螯合肽的作用下被转化为不具生物活性的无毒螯合物,另一方面在转运蛋白的作用下被转运至其他组织细胞或代谢活性较低的液泡内,减轻镉对原生质的集中性毒害,防止其破坏正常的生理生化反应;过量的镉则会引起植物体内的代谢紊乱,以及植物组织中活性氧增加,造成氧化胁迫。由超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)等组成的抗氧化系统可有效清除过量的活性氧,防止活性氧对细胞造成不可逆破坏。本文重点就植物应对镉胁迫的生理和分子机制及其调控网络进行综述,并对今后相关的研究和应用方向进行讨论,以期为植物响应镉胁迫的相关研究提供参考。

Heavy metal pollution,especially cadmium,is becoming increasingly serious.Cadmium is a non-essential element in plants,which can reduce photosynthetic capacity,leads to plant nutritional defects and oxidative stress,and subsequently results in growth retardation and even plant death.There is no specific transporter for cadmium in plants,and cadmium is generally transferred to the organs and tissues of plants by competing for the transporters of divalent metal ions such as zinc,iron,and calcium.After long-term evolution,plants have formed a set of complex mechanisms to deal with cadmium stress.The-COO-of pectin in the root cell wall can electrostatically combine with Cd2+,preventing cadmium from entering the protoplasm.After entering the protoplast,cadmium is transformed into non-bioactive or non-toxic chelates under the activity of phytochelatin.On the other hand,it is transported to other tissues or vacuoles with low metabolic activity under the action of transporters,thus reducing the concentrated toxicity of cadmium to protoplasts and preventing the destruction of physiological and biochemical reactions.Excessive cadmium will cause metabolic disorders,and the reactive oxygen species content in plant tissues increases to generate oxidative stress.The antioxidant system composed of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),and ascorbate peroxidase(APX)can effectively eliminate excess reactive oxygen species and prevent them from causing irreversible damage to cells.In this paper,the physiological and molecular mechanisms and regulatory networks of plant response to cadmium stress are reviewed.The related research and application perspectives in the future are discussed,providing a reference for studies on plant response to cadmium stress.