State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
Environ Sci Technol. 2022 May 17;56(10):6765-6773. doi: 10.1021/acs.est.2c00169. Epub 2022 Apr 28.
The bioaccumulation of the neurotoxin methylmercury (MeHg) in rice is a significant concern due to its potential risk to humans. Thiols have been known to affect MeHg bioavailability in microorganisms, but how thiols influence MeHg accumulation in rice plants remains unknown. Here, we investigated effects of common low-molecular-weight thiols, including cysteine (Cys), glutathione (GSH), and penicillamine (PEN), on MeHg uptake and translocation by rice plants. Results show that rice roots can rapidly take up MeHg, and this process is influenced by the types and concentrations of thiols in the system. The presence of Cys facilitated MeHg uptake by roots and translocation to shoots, while GSH could only promote MeHg uptake, but not translocation, by roots. Conversely, PEN significantly inhibited MeHg uptake and translocation to shoots. Using labeled Cys assays, we also found that MeHg uptake was coupled with Cys accumulation in rice roots. Moreover, analyses of comparative transcriptomics revealed that key genes associated with metallothionein and SULTR transporter families may be involved in MeHg uptake. These findings provide new insights into the uptake and translocation of MeHg in rice plants and suggest potential roles of thiol attributes in affecting MeHg bioavailability and bioaccumulation in rice.
甲基汞（MeHg）作为一种神经毒素，在水稻中的生物累积对人类健康存在潜在风险，这引起了人们的广泛关注。众所周知，巯基化合物会影响微生物中 MeHg 的生物利用度，但它们如何影响水稻植株中 MeHg 的积累尚不清楚。本研究调查了常见的低分子量巯基化合物，包括半胱氨酸（Cys）、谷胱甘肽（GSH）和青霉胺（PEN），对水稻吸收和转运 MeHg 的影响。结果表明，水稻根能够快速吸收 MeHg，而这一过程受到体系中巯基类型和浓度的影响。Cys 的存在促进了 MeHg 被根吸收和向地上部的转运，而 GSH 只能促进 MeHg 被根吸收，却不能促进其向地上部转运。相反，PEN 显著抑制了 MeHg 向地上部的吸收和转运。利用标记 Cys 实验，我们还发现 MeHg 的吸收与水稻根中 Cys 的积累有关。此外，比较转录组学分析表明，与金属硫蛋白和 SULTR 转运蛋白家族相关的关键基因可能参与 MeHg 的吸收。这些发现为水稻植株中 MeHg 的吸收和转运提供了新的见解，并提示巯基特性在影响 MeHg 生物利用度和生物累积方面的潜在作用。
