Tang Zhong, Wang Yijie, Gao Axiang, Ji Yuchen, Yang Baoyun, Wang Peng, Tang Zhu, Zhao Fang-Jie
State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China.
J Exp Bot. 2020 Sep 19;71(18):5631-5644. doi: 10.1093/jxb/eraa253.
Straighthead disease is a physiological disorder in rice with symptoms of sterile spikelets, distorted husks, and erect panicles. Methylated arsenic species have been implicated as the causal agent of the disease, but direct evidence is lacking. Here, we investigated whether dimethylarsinic acid (DMA) causes straighthead disease and its effect on the transcriptome of young panicles. DMA addition caused typical straighthead symptoms in hydroponic culture, which were alleviated by silicon addition. DMA addition to soil at the tillering to flowering stages induced straighthead disease. Transgenic rice expressing a bacterial arsenite methyltransferase gene gained the ability to methylate arsenic to mainly DMA, with the consequence of inducing straighthead disease. Field surveys showed that seed setting rate decreased with increasing DMA concentration in the husk, with an EC50 of 0.18 mg kg-1. Transcriptomic analysis showed that 364 and 856 genes were significantly up- and down-regulated, respectively, in the young panicles of DMA-treated plants compared with control, whereas Si addition markedly reduced the number of genes affected. Among the differentially expressed genes, genes related to cell wall modification and oxidative stress responses were the most prominent, suggesting that cell wall metabolism is a sensitive target of DMA toxicity and silicon protects against this toxicity.
直穗病是水稻的一种生理紊乱病害，症状表现为颖花不育、颖壳扭曲和穗直立。甲基化砷类物质被认为是该病的致病因子，但缺乏直接证据。在此，我们研究了二甲基胂酸（DMA）是否会引发直穗病及其对幼穗转录组的影响。在水培中添加DMA会导致典型的直穗症状，而添加硅可缓解这些症状。在分蘖期至开花期向土壤中添加DMA会诱发直穗病。表达细菌亚砷酸盐甲基转移酶基因的转基因水稻获得了将砷甲基化主要生成DMA的能力，结果诱发了直穗病。田间调查表明，随着颖壳中DMA浓度的增加，结实率降低，半数效应浓度（EC50）为0.18 mg kg-1。转录组分析显示，与对照相比，经DMA处理的植株幼穗中有364个基因显著上调，856个基因显著下调，而添加硅显著减少了受影响的基因数量。在差异表达基因中，与细胞壁修饰和氧化应激反应相关的基因最为突出，这表明细胞壁代谢是DMA毒性的敏感靶点，而硅可抵御这种毒性。
