Hg-Responsive Proteins Identified in Wheat Seedlings Using iTRAQ Analysis and the Role of ABA in Hg Stress

Wheat
seedlings exposed to 100 μM HgCl2 for 3
days exhibited high-level mercury (Hg) accumulation, which led to
inhibited growth, increased lipid peroxidation, and disrupted cellular
ultrastructures. And root growth and ultrastructural changes of wheat
seedlings were inhibited more severely than those of leaves. To identify
the wheat protein response to Hg stress, the iTRAQ method was used
to determine the proteome profiles of the roots and leaves of wheat
seedlings exposed to high-Hg conditions. 249 proteins were identified
with significantly altered abundance. 117 were found in roots and
132 in leaves. These proteins were classified into signal transduction,
stress defense, carbohydrate metabolism, protein metabolism, energy
production, and transport functional groups. The majority of proteins
identified in Hg-stressed roots and leaves displayed differently altered
abundance, revealing organ-specific differences in adaption to Hg
stress. Pathway Studio software was used to identify the Hg-responsive
protein interaction network that included 49 putative key proteins,
and they were potentially regulated by abscisic acid (ABA). Exogenous
ABA application conferred protection against Hg stress and increased
activities of peroxidase enzyme, suggesting that it may be an important
factor in the Hg signaling pathway. These findings can provide useful
insights into the molecular mechanisms of Hg responses in higher plants.

小麦幼苗经100 μM氯化汞（HgCl₂）处理3天后，会积累高水平的汞（Hg），进而出现生长受抑制、脂质过氧化水平升高以及细胞超微结构紊乱等现象。相较于叶片，小麦幼苗根部的生长与超微结构变化受抑制程度更为严重。为鉴定小麦响应汞胁迫的蛋白表达模式，本研究采用iTRAQ技术，对高汞胁迫下小麦幼苗根部与叶片的蛋白质组谱进行分析。共鉴定出249个丰度发生显著变化的蛋白，其中根部鉴定到117个，叶片鉴定到132个。这些蛋白可分为信号转导、胁迫防御、碳水化合物代谢、蛋白质代谢、能量产生以及转运等功能类群。汞胁迫下根部与叶片中鉴定出的多数蛋白的丰度变化模式存在差异，揭示了二者响应汞胁迫的器官特异性适应机制差异。通过Pathway Studio软件，本研究构建了包含49个潜在关键蛋白的汞响应蛋白互作网络，这些蛋白可能受脱落酸（abscisic acid，ABA）调控。外源施加脱落酸可缓解小麦幼苗遭受的汞胁迫，并提升过氧化物酶活性，提示脱落酸可能是汞信号通路中的重要调控因子。本研究结果可为解析高等植物响应汞胁迫的分子机制提供有价值的参考依据。