水稻根表铁膜及其形成的形态、生理及分子机理综述

A review on iron plaque on rice( Oryza sativa) root surface and the morphology,physiology and molecular biology of its formation mechanism

介绍了水稻铁吸收的两种机理、根表铁膜组成及其对生态环境和养分吸收意义。分析了影响铁膜形成的重要因素,即根系氧化力提升背后的两大基础:通气组织形成和酶介导的活性氧增加;说明了通气组织具有促进根系泌氧和缓解磷缺乏及铁中毒的作用,并指出,在铁膜形成过程中通气组织形成是活性氧增加引起细胞程序性死亡的结果。通过讨论抗氧化酶清除活性氧的功能,认为Fenton反应可能是铁膜形成的关键反应,提出了定位在表皮及外层皮层组织细胞壁上的III型过氧化物酶很可能与铁膜形成有密切联系的猜想。随后在分子层次上探讨了铁螯合还原-氧化酶、铁转运子及过氧化物酶等对铁膜形成所起的作用,认为类机理I铁吸收途径可能是铁膜形成所需铁的主要来源。概括了铁膜形成过程及条件,最后对铁膜研究中有待解决的热点问题进行了探讨。

This paper introduced two strategies of iron uptake in rice, the components of iron plaque on root surface and its significances for ecological environment and nutrient absorption. Two bases of iron plaque formation driven by increment of root oxidative capacity, i.e. formation of aerenchyma and the enzyme-mediated radical oxygen species （ROS） were analyzed emphatically. The formation of aerenchyma contributes to oxygen secretion enhancement as well as ameliorating phosphate deficiency and iron toxicity; besides, it also results in ROS-mediated programmed cell death. By analyzing ROS scavenge by antioxidant enzymes, Fenton reaction was assumed to be the key reaction in the process of iron plaque formation, and the hypothesis that the class III peroxidase located at cell wall of epidermis and outer cortex tissue might be associated with the formation of iron plaque on rice root surface was put forward. Moreover, the functions of iron chelate reduction oxidase, iron transporter and peroxidase at molecular level were discussed, and strategy I-like iron absorption pathway was regarded as a possible main source of iron for iron plaque formation. Finally, the hot spots needed to be solved on iron plaque were discussed after conclusively analyzing the process and condition of iron plaque formation.