State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, Center of Agricultural Health, Academy for Advanced Interdisciplinary, Jiangsu Provincial Key Laboratory for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, NO. 1 Weigang, Xuanwu district, Nanjing 210095, China.
School of Ecological and Environmental Sciences, East China Normal University, NO. 500 Dongchuan Street, Minghang, Shanghai 200241, China.
ISME J. 2024 Jan 8;18(1). doi: 10.1093/ismejo/wrae057.
Microbial arsenic (As) methylation in paddy soil produces mainly dimethylarsenate (DMA), which can cause physiological straighthead disease in rice. The disease is often highly patchy in the field, but the reasons remain unknown. We investigated within-field spatial variations in straighthead disease severity, As species in rice husks and in soil porewater, microbial composition and abundance of arsM gene encoding arsenite S-adenosylmethionine methyltransferase in two paddy fields. The spatial pattern of disease severity matched those of soil redox potential, arsM gene abundance, porewater DMA concentration, and husk DMA concentration in both fields. Structural equation modelling identified soil redox potential as the key factor affecting arsM gene abundance, consequently impacting porewater DMA and husk DMA concentrations. Core amplicon variants that correlated positively with husk DMA concentration belonged mainly to the phyla of Chloroflexi, Bacillota, Acidobacteriota, Actinobacteriota, and Myxococcota. Meta-omics analyses of soil samples from the disease and non-disease patches identified 5129 arsM gene sequences, with 71% being transcribed. The arsM-carrying hosts were diverse and dominated by anaerobic bacteria. Between 96 and 115 arsM sequences were significantly more expressed in the soil samples from the disease than from the non-disease patch, which were distributed across 18 phyla, especially Acidobacteriota, Bacteroidota, Verrucomicrobiota, Chloroflexota, Pseudomonadota, and Actinomycetota. This study demonstrates that even a small variation in soil redox potential within the anoxic range can cause a large variation in the abundance of As-methylating microorganisms, thus resulting in within-field variation in rice straighthead disease. Raising soil redox potential could be an effective way to prevent straighthead disease.
稻田土壤中的微生物砷（As）甲基化主要产生二甲砷酸（DMA），这可能导致水稻发生生理直头病。该疾病在田间通常呈高度斑块状分布，但原因尚不清楚。我们调查了两个稻田中直头病严重程度、稻壳和土壤孔隙水中砷形态、微生物组成以及编码亚砷酸盐 S-腺苷甲硫氨酸甲基转移酶的 arsM 基因丰度的田间空间变化。在两个田间，疾病严重程度的空间模式与土壤氧化还原电位、arsM 基因丰度、孔隙水中 DMA 浓度和稻壳 DMA 浓度的空间模式相匹配。结构方程模型确定土壤氧化还原电位是影响 arsM 基因丰度的关键因素，进而影响孔隙水中 DMA 和稻壳 DMA 浓度。与稻壳 DMA 浓度呈正相关的核心扩增子变体主要属于绿弯菌门、芽孢杆菌门、酸杆菌门、放线菌门和粘球菌门。来自疾病和非疾病斑块的土壤样本的宏基因组学分析鉴定了 5129 个 arsM 基因序列，其中 71%是转录的。arsM 携带宿主多种多样，主要是厌氧菌。在疾病土壤样本中，有 96-115 个 arsM 序列的表达显著高于非疾病土壤样本，这些序列分布在 18 个门中，特别是酸杆菌门、拟杆菌门、疣微菌门、绿弯菌门、假单胞菌门和放线菌门。本研究表明，即使在缺氧范围内土壤氧化还原电位的微小变化也会导致砷甲基化微生物丰度的大幅变化，从而导致水稻直头病的田间变化。提高土壤氧化还原电位可能是预防直头病的有效方法。
