Guangdong Provincial Key Laboratory of Aquatic Product Processing and Safety, College of food science and technology, Guangdong Ocean University, Zhanjiang, 524088, China.
Institute of Applied Microbiology, Jiangxi Agricultural University, Nanchang, 330045, China.
World J Microbiol Biotechnol. 2022 Oct 25;38(12):243. doi: 10.1007/s11274-022-03435-w.
Exopolysaccharides (EPSs) can be used as effective exogenous substances to alleviate the toxic effect of cadmium (Cd) on rice and other crops, thus improving plant growth characteristics under stress conditions, and reducing the accumulation of Cd in grains, but the underlying mechanism is still unclear. In the present work, the effects of EPSs from Lactobacillus plantarum on the efficiency of Cd absorption and distribution in rice seedlings under Cd stress were investigated. The results revealed that growth of rice seedlings was severely inhibited by exposure to Cd, resulting in the decrease of plant height, leaf length and biomass. This inhibition phenomenon was alleviated by the addition of EPSs from L. plantarum LPC-1. The underlying mechanism might be that EPSs could facilitate the accumulation efficiency of Cd in rice roots and reduce the transportation rate of Cd from root to leaves, therefore decreasing the Cd content in leaves. Further research showed that Cd contents in the cell wall fraction of the rice seedling root were increased by the addition of EPSs, while the proportions of Cd in the cell organelle and cell soluble component were reduced. Application of EPSs promotes the proportion of pectate- and protein- integrated Cd in rice roots. While the content of water-soluble Cd, which is more toxic to plants, decreased continuously both in roots and leaves. Our study clearly confirmed the positive effects of EPSs on alleviating Cd toxicity and decreasing Cd translocation in rice above-ground parts. Furthermore, the subcellular distribution and chemical forms of Cd in different rice seedlings parts were also affected by the addition of EPSs, which might be an important potential mechanism for EPSs in respect of alleviating Cd toxicity for rice. These findings provided a foundation for the application of exogenous substances on improving the growth performance of crops under heavy metal stress.
胞外多糖（EPSs）可用作有效外源物质来缓解镉（Cd）对水稻等作物的毒害作用，从而改善胁迫条件下植物的生长特性，降低谷物中 Cd 的积累，但其中的作用机制尚不清楚。本研究探讨了植物乳杆菌 EPSs 对 Cd 胁迫下水稻幼苗吸收和分配 Cd 效率的影响。结果表明，暴露于 Cd 会严重抑制水稻幼苗的生长，导致株高、叶长和生物量下降。这种抑制现象通过添加植物乳杆菌 LPC-1 的 EPSs 得到缓解。其作用机制可能是 EPSs 促进了 Cd 在水稻根部的积累效率，并降低了 Cd 从根部向叶片的运输速率，从而降低了叶片中的 Cd 含量。进一步的研究表明，添加 EPSs 增加了水稻幼苗根部细胞壁部分的 Cd 含量，而细胞细胞器和细胞可溶性成分中 Cd 的比例则降低。EPSs 的应用促进了水稻根部果胶和蛋白质结合 Cd 的比例。而对植物毒性更大的水溶性 Cd 含量在根部和叶片中均持续下降。本研究明确证实了 EPSs 对缓解水稻 Cd 毒性和降低地上部 Cd 转移的积极作用。此外，添加 EPSs 还影响了不同水稻幼苗部位 Cd 的亚细胞分布和化学形态，这可能是 EPSs 缓解水稻 Cd 毒性的一个重要潜在机制。这些发现为利用外源物质提高作物在重金属胁迫下的生长性能提供了基础。
