近日，華中農(nóng)業(yè)大學(xué)資源與環(huán)境學(xué)院劉玉榮教授課題組在水稻吸收甲基汞領(lǐng)域取得新的進(jìn)展，相關(guān)成果以“important roles of thiols in methylmercury uptake and translocation by rice plants”為題發(fā)表在Environmental Science & Technology上。

 

　　甲基汞（MeHg）具有強(qiáng)神經(jīng)毒性，可通過食物鏈在生物體內(nèi)累積和放大，從而威脅人類健康，食用大米是人類攝入MeHg的一個(gè)主要途徑。MeHg的生物有效性受環(huán)境因子，如低分子量巰基化合物（半胱氨酸Cys等）等溶解性有機(jī)質(zhì)影響。此外，稻米中的MeHg主要是以與Cys的結(jié)合態(tài)存在，從而可推測巰基化合物在水稻甲基汞積累過程中發(fā)揮著重要作用。然而，Cys等巰基化合物對水稻吸收和轉(zhuǎn)運(yùn)MeHg的影響及相關(guān)分子機(jī)制此前尚不清楚。

 

　　通過研究典型的低分子量巰基化合物對水稻MeHg吸收和轉(zhuǎn)運(yùn)的影響，課題組發(fā)現(xiàn)水稻根系能迅速吸收MeHg，這一過程受體系中巰基化合物類型和濃度的影響。Cys的存在促進(jìn)了根對MeHg的吸收和向地上部的轉(zhuǎn)運(yùn)；谷胱甘肽只能促進(jìn)MeHg的吸收而不能促進(jìn)轉(zhuǎn)運(yùn)；相反，PEN顯著抑制了MeHg的吸收和轉(zhuǎn)運(yùn)。通過分析用13C標(biāo)記的Cys，研究發(fā)現(xiàn)水稻對MeHg的吸收與Cys在根系中的積累有關(guān)。通過轉(zhuǎn)錄組學(xué)比較分析，課題組發(fā)現(xiàn)了74個(gè)基因發(fā)生顯著變化，其中3個(gè)基因在Cys的作用下進(jìn)一步上調(diào)，由此推斷金屬硫蛋白和硫轉(zhuǎn)運(yùn)蛋白相關(guān)基因可能參與水稻對MeHg的吸收。這些發(fā)現(xiàn)增加了對水稻吸收MeHg的認(rèn)知，為稻田汞污染調(diào)控提供了重要的理論依據(jù)。

 

　　資源與環(huán)境學(xué)院博士研究生郝蕓蕓為論文第一作者，劉玉榮教授為通訊作者，美國橡樹嶺國家實(shí)驗(yàn)室顧寶華教授、華中農(nóng)業(yè)大學(xué)王創(chuàng)教授，馮嬌副研究員、黃巧云教授、本科生朱玉杰、嚴(yán)若群等也參與了該項(xiàng)研究。該研究得到了國家自然科學(xué)基金和華中農(nóng)業(yè)大學(xué)人才引進(jìn)項(xiàng)目資助。

 

　　【英文摘要】

 

　　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 13Cys 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.

 

　　原文鏈接：https://pubs.acs.org/doi/10.1021/acs.est.2c00169