腐殖酸缓解茶树铅胁迫的调控机理
2020-10-09 作者: admin 来源: 未知 已阅读次
Though the interaction between humic acid (HA) andheavy metals has been widely reported, the effects of HA on the toxicity ofheavy metals to plants are still in debate. In this study, the regulation mechanisms of HA on Pb stress in tea plant (Camellia sinensis L.) was investigated through hydroponic experiments, and the experimental results were explained by using transmission electron microscope (TEM), scanning transmission X-ray microscopes (STXM) and isobaric tags for relative and absolute quantitation (iTRAQ) differential proteomics. Significant alleviation of Pb stress was found with HA coexistence. TEM results showed that HA greatly mitigated the damage of cells caused by Pb stress. Compared with sole Pb treatment, the addition of HA increased the contents of pectin and pectic acidin the cell wall by 10.5% and 30.5%, while arabinose (Ara) and galactose (Gal) decreased by 20.5% and 15.9%, respectively, which were beneficial for increasing Pb adsorption capacity of the cell wall and promoting cell elongation. Moreover, iTRAQ differential proteomics analysis proved that HA strengthened the antioxidant system, promoted the synthesis of cell wall, and stabilized protein and sulfur-containing substance metabolism in molecular level. Notably, the concentration of calcium (Ca) in the cell wall of HA coexistence treatment was 47.4% higher than Pb treatment. STXM results also indicated that the distribution of Ca in the cell wall was restored with the presence of HA. This might promote the formation of the egg-box model, thus alleviating Pb stress in cells. Our results reveal the regulation mechanisms of HA on Pb detoxification in plants and provide useful information for improving the safety of agricultural products.
尽管腐植酸（HA）与重金属的相互作用已被广泛报道，但腐植酸对重金属对植物毒性的影响仍存在争议。本研究通过水培试验，并用透射电镜（TEM）、扫描透射电镜（STXM）和同位素标记相对和绝对定量（iTRAQ）差异蛋白质组学研究了HA对茶树铅胁迫的调控机制。HA共存对Pb胁迫有显著缓解作用。TEM结果表明，HA能显著减轻Pb胁迫对细胞的损伤。与单一Pb处理相比，HA使细胞壁中果胶和果胶酸含量分别提高了10.5%和30.5%，阿拉伯糖（Ara）和半乳糖（Gal）分别降低了20.5%和15.9%，有利于提高细胞壁对铅的吸附能力，促进细胞的伸长。此外，iTRAQ差异蛋白质组学分析表明HA在分子水平上增强了抗氧化系统，促进了细胞壁的合成，稳定了蛋白质和含硫物质的代谢。值得注意的是，HA共存处理的细胞壁钙浓度比Pb处理高47.4%。STXM结果还表明，HA的存在使Ca在细胞壁上的分布得以恢复。这可能促进卵盒模型的形成，从而减轻细胞内铅胁迫。研究结果揭示了腐植酸对植物铅解毒的调节机制，为提高农产品安全性提供了有益的信息。
责任编辑：千鹤茶苗