植物螯合肽及其在重金属耐性中的作用

Phytochelatin and its function in heavy metal tolerance of higer plants

综述植物螯合肽的生物合成及其在重金属耐性中的作用 .有毒重金属在土壤中的积累不仅影响作物的生长和产量形成 ,而且严重威胁农产品的安全性 .植物对重金属的耐性和积累在种间和基因型之间存在着很大的差异 ,在重金属胁迫条件下植物螯合肽 (PC)的合成是植物对胁迫的一种适应性反应 ,耐性基因型合成较多的PC .谷胱甘肽是合成PC的前体 ,PC可与重金属螯合 ,并进一步转运至液泡贮存 ,使细胞质的重金属浓度降低 ,从而达到解毒效果 .重金属诱导植物合成PC的遗传机理和生化途径有赖于分子生物学的深入研究 ,Cd 敏感型拟南芥突变体Cad1 1(缺失GSH)和Cad2 1(缺失PC合成诱导酶 )的分离及相关研究 ,佐证了PC在Cd 解毒中起关键作用 .对PC在重金属污染土壤或水体的植物修复和农作物安全生产中的意义进行了讨论 .

The biosynthesis pathway of phytochelatins (PC) and its function in heavy metal tolerance of higher plants were summarized in this paper. The toxic heavy metal accumulation in soil would deteriorates crop growth and yield components, and threaten the agro-products security. There were significantly differences in the accumulation and tolerance to heavy metals among plant species and genotypes. The formation of PC in response to the stress caused by heavy metals was one of the truly adaptive responses occurred commonly in higher plants. In the heavy metal tolerant genotypes, there was a much higher accumulation of PC than the non-tolerant lines. Glutathione (GSH) was the substrate for the synthesis of PC, which chelated the metals. The inactive toxic metal ions of metal-PC chelatins were subsequently transported from cytosol to vacuole before they could poison the enzymes of life-supporting metabolic routes, and transiently stored in vacuole to reduce the heavy metal concentration in cytosol, thus, heavy metal detoxification was attained. The break through of genetic mechanism and bio-chemical pathway of PC synthesis induced by heavy metals would depend on the further study on molecular biology in this field. The isolation of Cd-sensitive cad1 and cad2 mutants of Arabidopsis thaliana, that was deficient in PC, demonstrted the importance of PC for heavy metal tolerance. The effect of PC on food security and on phytoremediation of soil and water contaminated by heavy metals was also discussed in this paper.