Verma Pratima, Singh Amrita, Purru Supriya, Bhat Kangila Venkataramana, Lakhanpaul Suman
Department of Botany, University of Delhi, New Delhi 110007, India.
Department of Botany, Gargi College, University of Delhi, New Delhi 110049, India.
Biology (Basel). 2022 Jun 23;11(7):954. doi: 10.3390/biology11070954.
Phytoplasma-associated diseases such as phyllody and little leaf are critical threats to sesame cultivation worldwide. The mechanism of the dramatic conversion of flowers to leafy structures leading to yield losses and the drastic reduction in leaf size due to Phytoplasma infection remains yet to be identified. Cytosine methylation profiles of healthy and infected sesame plants studied using Whole Genome Bisulfite Sequencing (WGBS) and Quantitative analysis of DNA methylation with the real-time PCR (qAMP) technique revealed altered DNA methylation patterns upon infection. Phyllody was associated with global cytosine hypomethylation, though predominantly in the CHH (where H = A, T or C) context. Interestingly, comparable cytosine methylation levels were observed between healthy and little leaf-affected plant samples in CG, CHG and CHH contexts. Among the different genomic fractions, the highest number of differentially methylated Cytosines was found in the intergenic regions, followed by promoter, exonic and intronic regions in decreasing order. Further, most of the differentially methylated genes were hypomethylated and were mainly associated with development and defense-related processes. Loci for STOREKEEPER protein-like, a DNA-binding protein and PP2-B15, an F-Box protein, responsible for plugging sieve plates to maintain turgor pressure within the sieve tubes were found to be hypomethylated by WGBS, which was confirmed by methylation-dependent restriction digestion and qPCR. Likewise, serine/threonine-protein phosphatase-7 homolog, a positive regulator of cryptochrome signaling involved in hypocotyl and cotyledon growth and probable O-methyltransferase 3 locus were determined to be hypermethylated. Phytoplasma infection-associated global differential methylation as well as the defense and development-related loci reported here for the first time significantly elucidate the mechanism of phytoplasma-associated disease development.
诸如变叶病和小叶病等与植原体相关的病害是全球芝麻种植面临的重大威胁。由于植原体感染导致花朵急剧转变为叶状结构从而造成产量损失以及叶片大小急剧减小的机制仍有待确定。使用全基因组亚硫酸氢盐测序（WGBS）和实时PCR（qAMP）技术对DNA甲基化进行定量分析，研究健康和受感染芝麻植株的胞嘧啶甲基化谱，结果显示感染后DNA甲基化模式发生了改变。变叶病与整体胞嘧啶低甲基化有关，不过主要是在CHH（其中H = A、T或C）背景下。有趣的是，在CG、CHG和CHH背景下，健康和受小叶病影响的植株样本之间观察到了相当的胞嘧啶甲基化水平。在不同的基因组部分中，差异甲基化胞嘧啶数量最多的是基因间区域，其次是启动子、外显子和内含子区域，顺序递减。此外，大多数差异甲基化基因是低甲基化的，主要与发育和防御相关过程有关。通过WGBS发现，负责堵塞筛板以维持筛管内膨压的类贮藏蛋白样DNA结合蛋白和F-Box蛋白PP2-B15的位点是低甲基化的，这通过甲基化依赖性限制性消化和qPCR得到证实。同样，参与下胚轴和子叶生长的隐花色素信号的正调节因子丝氨酸/苏氨酸蛋白磷酸酶-7同源物以及可能的O-甲基转移酶3位点被确定为高甲基化。本文首次报道的与植原体感染相关的整体差异甲基化以及与防御和发育相关的位点，显著阐明了与植原体相关病害的发生机制。
