无机砷在植物体内的吸收和代谢机制

砷污染已成为全球非常突出且急需解决的环境问题,严重威胁人类健康和环境安全.在自然环境和土壤系统中,砷的存在形态相当复杂,但植物砷毒害主要源于As(Ⅴ)和As(Ⅲ)暴露.As(Ⅴ)通过Pi的吸收通道被植物根系吸收,并在还原酶(AR)作用下被快速还原为As(Ⅲ).As(Ⅲ)通过NIP蛋白通道进入植物体内,在砷甲基转移酶(ArsM)的作用下转化为甲基化砷或与谷胱甘肽(GSH)、植物螯合肽(PC)等多肽的巯基螯合封存在根部液泡或转运到地上部分,从而起到砷解毒的作用.同时,植物吸收的一部分砷也可外排到外部介质.本文以农作物尤其是水稻为主线,详述了As(Ⅴ)和As(Ⅲ)吸收、外排及As(Ⅴ)还原、As(Ⅲ)甲基化、螯合作用的最新研究进展,并提出了今后的研究重点.

Absorption and metabolism mechanisms of inorganic arsenic in plants: a review

Arsenic pollution seriously threatens human health and environment safety, being a very prominent environmental issue to be urgently solved in the world. In natural environment and soil systems, arsenic exists in complicated forms, but the plant arsenic poisoning is mainly from As(V) and As (III) exposure. As(V) can be absorbed by plant roots through Pi channel, and reduced rapidly to As(III) by arsenate reductase. As( III) can be transported into plants through NIP channel, and subsequently either transformed into methylated arsenic by arsenic methyltransferase or chelated with the thiol of GSH and PCs. These arsenic compounds can be sequestrated in root cell vacuoles or transported to plant aerial parts. Meanwhile, a part of absorbed arsenic can be discharged to external media. All of these can help to detoxify the arsenic in plants. This paper reviewed the latest research progress on the arsenic- resistance of crops, especially rice, with the focus on the mechanisms of As(V) and As(Ill) absorption and excretion, As(V) reduction, and As (II) methylation and chelation. The major topics of future research on arsenic toxicity were proposed.