MOE Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
School of Marine Sciences, Ningbo University, Ningbo 315211, China.
Environ Int. 2020 Oct;143:105912. doi: 10.1016/j.envint.2020.105912. Epub 2020 Jul 7.
Lead (Pb) contamination presents a widespread environmental plague. Sedum alfredii is widely used for soil phytoremediation owing to its capacity to extract heavy metals, such as Pb. Although efficient Pb extraction is mediated by complex interactions between the roots and rhizospheric bacteria, the mechanism by which S. alfredii recruits microorganisms under Pb stress remains unclear. The Pb-accumulating ecotype (AE) and non-accumulating ecotype (NAE) of S. alfredii recruited different rhizobacterial communities. Under Pb stress, AE rhizosphere-enriched bacteria assembled into stable-connected clusters with higher phylogenetic and functional diversity. These microbes, e.g., Flavobacterium, could release indoleacetic acid to promote plant growth and siderophores, thereby increasing Pb availability. The NAE rhizosphere-enriched functional bacteria "desperately" assembled into highly specialized functional clusters with extremely low phylogenetic diversity. These bacteria, e.g., Pseudomonas, could enhance phosphorus solubilization and Pb precipitation, thereby reducing Pb stress and plant Pb accumulation. High niche overlap level of the rhizo-enriched species raised challenges in soil resource utilization, whereas the NAE community assembly was markedly constrained by environmental "selection effect" than that of AE rhizobacterial community. These results indicate that different ecotypes of S. alfredii recruit distinct bacterial functional assemblies to drive specific plant-soil feedbacks for different survival in Pb-contaminated soils. To cope with heavy metal stress, NAE formed a highly functional and specialized but vulnerable community and efficiently blocked heavy metal absorption by plants. However, the AE community adopted a more stable and elegant strategy to promote plant growth and the accumulation of dry matter via multiple evolutionary strategies that ensured a high yield of heavy metal phytoextraction. This for the first time provides new insights into the roles of rhizosphere microbes in plant adaptations to abiotic stresses.
铅（Pb）污染是一种广泛存在的环境问题。由于其能够提取重金属（如 Pb），垂盆草被广泛用于土壤植物修复。虽然有效的 Pb 提取是通过根和根际细菌之间的复杂相互作用介导的，但 S. alfredii 在 Pb 胁迫下招募微生物的机制尚不清楚。S. alfredii 的 Pb 积累生态型（AE）和非积累生态型（NAE）招募了不同的根际细菌群落。在 Pb 胁迫下，AE 根际富集细菌形成了稳定连接的群落，具有更高的系统发育和功能多样性。这些微生物，如黄杆菌，可以释放吲哚乙酸来促进植物生长和铁载体，从而增加 Pb 的可用性。NAE 根际富集功能细菌“拼命”组装成高度专业化的功能群，具有极低的系统发育多样性。这些细菌，如假单胞菌，可以增强磷的溶解和 Pb 的沉淀，从而降低 Pb 胁迫和植物 Pb 积累。根际富物种的高生态位重叠水平给土壤资源利用带来了挑战，而与 AE 根际细菌群落相比，NAE 群落组装明显受到环境“选择效应”的限制。这些结果表明，S. alfredii 的不同生态型招募了不同的细菌功能组装体，以驱动特定的植物-土壤反馈，从而在 Pb 污染土壤中实现不同的生存。为了应对重金属胁迫，NAE 形成了一个高度功能化和专业化但脆弱的群落，并有效地阻止了植物对重金属的吸收。然而，AE 群落通过多种进化策略采用了一种更稳定和优雅的策略来促进植物生长和干物质积累，从而确保了重金属植物提取的高产量。这首次为根际微生物在植物适应非生物胁迫中的作用提供了新的见解。
