Epigenetic Regulation of ABA-Induced Transcriptional Responses in Maize
Epigenetic Regulation of ABA-Induced Transcriptional Responses in Maize
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DOI：
10.1534/g3.119.400993
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发表时间：
2020-03
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影响因子：
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通讯作者：
Stefania Vendramin;Ji Huang;Peter A. Crisp;Thelma F. Madzima;K. McGinnis
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作者：
Stefania Vendramin;Ji Huang;Peter A. Crisp;Thelma F. Madzima;K. McGinnis
植物要承受极端的环境条件，必须快速适应。植物激素脱落酸 (ABA) 在非生物胁迫期间积累，发出触发生理反应的转录变化信号。表观遗传修饰通常促进转录，特别是在表现出时间、组织特异性和环境诱导表达的基因上。在玉米 (Zea mays) 中，副突变介体 1 (MOP1) 是 RNA 依赖性表观遗传途径进展所必需的，该途径调节全基因组基因座的转录沉默。 MOP1 功能先前已与邻近特定类型转座元件和基因区域的基因组区域相关，表明该调控途径的功能是维持基因组空间内不同的转录活性，并且 MOP1 的丢失可能会改变某些位点对其他调控途径的反应性。作为基因表达的关键调节因子，MOP1 和 ABA 途径各自调节特定基因。为了确定 MOP1 的缺失是否影响玉米中 ABA 响应基因的表达，对 mop1-1 和 Mop1 纯合幼苗进行了外源 ABA 和 RNA 测序。在四次配对比较中总共鉴定出 3,242 个差异表达基因 (DEG)。总体而言，在 mop1-1 纯合植物中，ABA 诱导的基因表达变化得到增强。在 ABA 诱导的 mop1-1 突变体中发现了最多数量的 DEG，包括许多转录因子；这表明组合调控方案包括对遗传破坏（mop1-1）的直接和间接转录反应和/或响应基因的分层级联网络的刺激诱导。此外，在一些基因型中观察到响应 ABA 的假定 MOP1-RdDM 位点的 CHH 甲基化适度增加，表明表观遗传变异可能影响玉米中环境诱导的转录反应。
Plants are subjected to extreme environmental conditions and must adapt rapidly. The phytohormone abscisic acid (ABA) accumulates during abiotic stress, signaling transcriptional changes that trigger physiological responses. Epigenetic modifications often facilitate transcription, particularly at genes exhibiting temporal, tissue-specific and environmentally-induced expression. In maize (Zea mays), MEDIATOR OF PARAMUTATION 1 (MOP1) is required for progression of an RNA-dependent epigenetic pathway that regulates transcriptional silencing of loci genomewide. MOP1 function has been previously correlated with genomic regions adjoining particular types of transposable elements and genic regions, suggesting that this regulatory pathway functions to maintain distinct transcriptional activities within genomic spaces, and that loss of MOP1 may modify the responsiveness of some loci to other regulatory pathways. As critical regulators of gene expression, MOP1 and ABA pathways each regulate specific genes. To determine whether loss of MOP1 impacts ABA-responsive gene expression in maize, mop1-1 and Mop1 homozygous seedlings were subjected to exogenous ABA and RNA-sequencing. A total of 3,242 differentially expressed genes (DEGs) were identified in four pairwise comparisons. Overall, ABA-induced changes in gene expression were enhanced in mop1-1 homozygous plants. The highest number of DEGs were identified in ABA-induced mop1-1 mutants, including many transcription factors; this suggests combinatorial regulatory scenarios including direct and indirect transcriptional responses to genetic disruption (mop1-1) and/or stimulus-induction of a hierarchical, cascading network of responsive genes. Additionally, a modest increase in CHH methylation at putative MOP1-RdDM loci in response to ABA was observed in some genotypes, suggesting that epigenetic variation might influence environmentally-induced transcriptional responses in maize.