| 稻田落干过程砷甲基化效率变化与关键影响因素分析 |
| 摘要点击 1299 全文点击 370 投稿时间：2021-11-14 修订日期：2022-01-26 |
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| 中文关键词 孔隙水 砷甲基化效率 水稻秸秆 砷甲基化基因(arsM) 硫酸盐还原基因(dsrA) |
| 英文关键词 porewater As methylation efficiency rice straw As-methylating gene (arsM) sulfate-reducing gene (dsrA) |
| 作者 | 单位 | E-mail | | 张玥 | 中国农业科学院农业环境与可持续发展研究所, 农业农村部农业环境重点实验室, 北京 100081 | zhangyue06@caas.cn | | 李令仪 | 中国农业科学院农业环境与可持续发展研究所, 农业农村部农业环境重点实验室, 北京 100081 | | | 文炯 | 岳阳市农业科学研究院, 农业农村部岳阳农业环境科学观测实验站, 岳阳 414000 | | | 曾希柏 | 中国农业科学院农业环境与可持续发展研究所, 农业农村部农业环境重点实验室, 北京 100081 | | | 苏世鸣 | 中国农业科学院农业环境与可持续发展研究所, 农业农村部农业环境重点实验室, 北京 100081 | sushiming@caas.cn |
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| 中文摘要 |
| 研究稻田落干过程砷甲基化效率变化规律，分析关键环境和生物因素的影响，为今后水稻直穗病防控提供科学依据.开展室内培养模拟稻田落干过程，以采集自贵州兴仁（XR）和广西南丹（ND）的两种砷污染水稻土壤为供试土壤，各土壤设置添加（RS）和不添加（CK）水稻秸秆处理，分析自然落干0、24、36、48和60 h过程中Eh、pH、孔隙水总有机碳（TOC）、砷形态、砷甲基化功能基因（arsM）、硫酸盐还原菌（dsrA，砷甲基化相关微生物）、产甲烷菌（mcrA，砷去甲基化相关微生物）丰度和arsM功能微生物多样性变化.稻田落干过程土壤Eh由完全淹水状态下的-300~-200 mV向落干后的-150~-50 mV变迁，而pH值变化规律不明显；孔隙水无机砷（iAs）和二甲基砷（DMAs）浓度随落干过程变化更为显著，总体呈现增加趋势，且RS处理DMAs浓度显著高于CK，ND土壤孔隙水比XR土壤孔隙水DMAs浓度更高；随落干时间延长，XR-CK和XR-RS处理土壤砷甲基化效率有一定提升，但变化不显著，而ND-CK和ND-RS处理土壤砷甲基化效率显著增加.当培养为60 h时，ND-CK和ND-RS处理砷甲基化效率相比培养初期分别提高约61.8%和23.2%；随落干时间延长arsM和dsrA基因拷贝数明显增加，而mcrA基因拷贝数显著下降.秸秆添加后显著提高全细菌和arsM、dsrA和mcrA基因丰度；进一步基于多因素方差分析和冗余分析发现，供试土壤、秸秆添加、落干时间和其交互作用对于各砷形态、砷甲基化效率和关键基因丰度变化影响显著，TOC、Eh和砷甲基化相关基因与甲基态砷呈正向关联，而与无机砷iAs呈负向关联；基于arsM微生物测序发现，伴随落干过程还发生着砷甲基化功能微生物群落的更替.研究结果有助于提升稻田落干过程中砷甲基化变化的理论认知，为今后水稻直穗病科学防控提供指导. |
| 英文摘要 |
| The straight head disease of rice is one of the main problems limiting rice production. Arsenic (As) methylation in paddy soils is considered to be highly related to the occurrence of the straight head disease. As a typical field practice, rice fields are usually drained during the late tillering stage and the mid-late grain filling stage. Nevertheless, the key influencing factors on the As methylation efficiency during paddy soil drying remain unclear. In this study, an indoor cultivation experiment was set up to simulate the drying process of paddy soil. Two As-contaminated soils collected from Xingren (XR) in Guizhou province and Nandan (ND) in Guangxi province were used as test soils. Each soil was treated with the addition of rice straw (RS) and without rice straw (CK). With the drying of paddy soil (0, 24, 36, 48, and 60 h), the changes in soil Eh, pH, total organic carbon (TOC), and As chemical species in the porewater were determined. The abundance of the As methylation functional gene (arsM), sulfate-reducing bacteria (harboring dsrA, As methylation-related microorganism), and methanogens (harboring mcrA, As demethylation-related microorganism), as well as the diversity of arsM-harboring microorganisms, were also observed. The results showed that during the process of drying paddy soil, soil Eh changed from -300——200 mV under complete flooding to -150——50 mV after drying; however, the change in soil pH was not obvious. The concentrations of inorganic As (iAs) and dimethylarsenic (DMAs) in porewater significantly increased (P<0.05) with the drying process. Additionally, the concentration of DMAs in the RS treatment was prominently higher than that in CK. Compared with XR soil, the concentration of DMAs in ND soil was higher. As a function of soil drying time, the As methylation efficiency of XR soil (XR-CK and XR-RS) slightly increased but was not significant (P>0.05), whereas the As methylation efficiency of ND soil (ND-CK and ND-RS) increased significantly (P<0.05). After the drying time reached 60 h, the As methylation efficiency of ND-CK and ND-RS increased by 61.8% and 23.2%, respectively, compared with those at the early stage of drying (0 hours). The copy numbers of the arsM and dsrA genes greatly increased with the extension of drying time, whereas an opposite trend was observed for the copy number of the mcrA gene. Furthermore, the addition of straw obviously increased the gene abundance of whole bacteria and arsM-, dsrA-, and mcrA-harboring bacteria. Based on the multi-factor analysis of variance and the redundancy analysis, it was found that the test soil type, straw addition, drying time, and their interaction had a critical influence on the changes in As species, As methylation efficiency, and the gene abundance in soils. TOC, Eh, and the functional genes associated with As methylation were positively linked with the methylated As content in soil porewater but negatively correlated with that of iAs. According to the sequence of the arsM-harboring microbe, it was clearly demonstrated that a community shift of As-methylating microbe occurred with the soil drying. Here, the following conclusions were derived:① the drying process did not lower the As methylation efficiency in paddy soil. On the contrary, in this study, the As methylation efficiency, especially that for ND soil, remarkably improved. The addition of straw notably promoted the As methylation efficiency and the content of DMAs in porewater. ② An increasing tendency was observed for the abundance of microbes related to As methylation, whereas a reverse trend was indicated for microbes related to As demethylation. The community shift of arsM-harboring microbes might be the crucial reason for the improved As methylation efficiency during the soil drying. These observations contribute to a better understanding of the As methylation process during paddy soil drying and will shed light on the future mitigation of rice straight head disease in paddy soils. |
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