Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou, 310058, China; National Demonstration Center for Experimental Environment and Resources Education, Zhejiang University, Hangzhou, 310058, China.
Environ Pollut. 2021 Jan 1;268(Pt A):115665. doi: 10.1016/j.envpol.2020.115665. Epub 2020 Sep 18.
Root cell wall (RCW) modification is a widespread important defense strategy of plant to cope with trace metals. However, mechanisms underlying its remolding in cadmium (Cd) accumulation are still lacking in hyperaccumulators. In this study, changes of RCW structures and components between nonhyperaccumulating ecotype (NHE) and hyperaccumulating ecotype (HE) of Sedum alfredii were investigated simultaneously. Under 25 μM Cd treatment, RCW thickness of NHE is nearly 2 folds than that of HE and the thickened cell wall of NHE was enriched in low-methylated pectin, leading to more Cd trapped in roots tightly. In the opposite, large amounts of high-methylated pectin were assembled around RCW of HE with Cd supply, in this way, HE S. alfredii decreased its root fixation of Cd and enhanced Cd migration into xylem. TEM and AFM results further confirmed that thickened cell wall was caused by the increased amounts of cellulose and lignin while root tip lignification was resulted from variations of sinapyl (S) and guaiacyl (G) monomers. Overall, thickened cell wall and methylated pectin have synchronicity in spatial location of roots, and their coordination contributed to Cd accumulation in S. alfredii.
根细胞壁（RCW）的修饰是植物应对痕量金属的一种广泛而重要的防御策略。然而，在超积累植物中，其在镉（Cd）积累过程中的重塑机制仍然缺乏。在本研究中，我们同时研究了非超积累生态型（NHE）和超积累生态型（HE）的垂盆草之间 RCW 结构和成分的变化。在 25 μM Cd 处理下，NHE 的 RCW 厚度是 HE 的近 2 倍，并且 NHE 中细胞壁的增厚富含低甲基化果胶，从而将更多的 Cd 紧紧地固定在根部。相反，随着 Cd 的供应，大量的高甲基化果胶在 HE 的 RCW 周围组装，从而降低了 HE S.alfredii 对 Cd 的根固定，并增强了 Cd 向木质部的迁移。TEM 和 AFM 结果进一步证实，细胞壁的增厚是由于纤维素和木质素含量的增加所致，而根尖木质化则是由于松柏醇（S）和愈创木酚（G）单体的变化所致。总的来说，增厚的细胞壁和甲基化果胶在根部的空间位置上具有同步性，它们的协调作用有助于 Cd 在垂盆草中的积累。
