Subcellular distribution, chemical forms of cadmium and rhizosphere microbial community in the process of cadmium hyperaccumulation in duckweed
Subcellular distribution, chemical forms of cadmium and rhizosphere microbial community in the process of cadmium hyperaccumulation in duckweed
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DOI：
10.1016/j.scitotenv.2022.160389
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发表时间：
2022-11-23
影响因子：
9.8
通讯作者：
Yang，Gui-Li
中科院分区：
文献类型：
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作者：
Zheng，Meng-Meng;Feng，Dan;Yang，Gui-Li
浮萍是一种新发现的镉超积累植物，生长迅速，但其耐性和解毒机制尚不清楚。本研究通过对浮萍体内Cd的组织、亚细胞和化学形态分布的研究，探讨了Cd对浮萍生长、超微结构和根际微生物群落的影响。结果表明，镉对浮萍的生长有一定的抑制作用，使根长缩短。Cd在根中的积累量大于在叶中的积累量，且随着时间的推移，Cd从根向叶转移。在12-24 h内，Cd主要存在于细胞壁组分（2.05%~ 95.52%）和细胞器组分（5.03%~ 97.80%）中，其次是可溶性组分（0.14%~ 16.98%）。随着时间的推移，Cd在细胞器中的比例增加（46.64%-92.83%），超过了在细胞壁中的比例（6.79%-66.23%），表明浮萍解毒机制可能与细胞壁和液泡的滞留有关。Cd的主要化学形态为NaCl浸提态（30.15%~ 88.66%），与果胶和蛋白质结合在一起。随着胁迫浓度和胁迫时间的增加，盐酸提取态和醋酸提取态镉所占比例增加，分别为低毒的草酸镉和磷酸镉。镉损伤了浮萍根际叶绿体、线粒体等细胞的超微结构，抑制了根际微生物群落的多样性，但能耐受重金属的优势种群有所增加。据推测，浮萍分布在一个较小的活性位置，主要是通过在根细胞壁和隔离在叶液泡中的毒性较小的化学形式的镉，并动态调整。根际微生物群落对重金属的耐受性也可能是浮萍对镉耐受的机制之一。本研究从分子水平揭示了浮萍对镉的耐受和解毒机制，为浮萍的进一步开发利用提供了理论依据。
Duckweed is a newly reported Cd hyperaccumulator that grow rapidly; however, little is known about its tolerance and detoxification mechanisms. In this study, we investigated the tissue, subcellular, and chemical form distribution of the Cd in duckweed and studied the influences of Cd on duckweed growth, ultrastructure, and rhizosphere microbial community. The results showed that Cd could negatively affect the growth of duckweed and shorten the root length. More Cd accumulated in the roots than in the leaves, and Cd was transferred from the roots to the leaves with time. During 12–24 h, Cd mainly existed in the cell wall fraction (2.05 %–95.52 %) and the organelle fraction (5.03 %–97.80 %), followed the soluble fraction (0.14 %–16.98 %). Over time, the proportion of Cd in the organelles increased (46.64 %–92.83 %), exceeding that in the cell wall (6.79 %–66.23 %), which indicated that duckweed detoxification mechanism may be related to the retention of cell wall and vacuole. The main chemical form of Cd was the NaCl-extracted state (30.15 %–88.66 %), which was integrated with pectate and protein. With increasing stress concentration and time, the proportion of the HCl-extracted state and HAc-extracted state increased, and they were low-toxic Cd oxalate and Cd phosphate, respectively. Cd damaged the ultrastructure of cells such as chloroplasts and mitochondria and inhibited the diversity of microbial communities in the duckweed rhizosphere; however, the dominant populations that could tolerate heavy metals increased. It was speculated that duckweed distributed Cd in a less toxic chemical form in a less active location, mainly through retention in the root cell wall and sequestration in the leaf vacuoles, and is dynamically adjusted. The rhizosphere microbial communities tolerate heavy metals may also be one of the mechanisms by which duckweed can tolerate Cd. This study revealed the mechanism of duckweed tolerance and detoxification of Cd at the molecular level and provides a theoretical basis for further development of duckweed.