PDF(Pubmed)
Abstract：
Heterochromatin is critical for maintaining genome stability, especially in flowering plants, where it relies on a feedback loop involving the H3K9 methyltransferase, KRYPTONITE (KYP), and the DNA methyltransferase CHROMOMETHYLASE3 (CMT3). The H3K9 demethylase INCREASED IN BONSAI METHYLATION 1 (IBM1) counteracts the detrimental consequences of KYP-CMT3 activity in transcribed genes. IBM1 expression in Arabidopsis is uniquely regulated by methylation of the 7th intron, allowing it to monitor global H3K9me2 levels. We show the methylated intron is prevalent across flowering plants and its underlying sequence exhibits dynamic evolution. We also find extensive genetic and expression variations in KYP, CMT3, and IBM1 across flowering plants. We identify Arabidopsis accessions resembling weak ibm1 mutants and Brassicaceae species with reduced IBM1 expression or deletions. Evolution towards reduced IBM1 activity in some flowering plants could explain the frequent natural occurrence of diminished or lost CMT3 activity and loss of gene body DNA methylation, as cmt3 mutants in A. thaliana mitigate the deleterious effects of IBM1.
摘要：
异染色质是维持基因组稳定性的关键,尤其是在开花植物中，它依赖于涉及H3K9甲基转移酶的反馈回路，KRYPTonite(KYP),和DNA甲基转移酶氯甲基酶3(CMT3)。在BONSAI甲基化1（IBM1）中增加的H3K9脱甲基酶抵消了转录基因中KYP-CMT3活性的有害后果。拟南芥中IBM1的表达受到第7内含子甲基化的独特调控,允许它监控全球H3K9me2水平。我们表明甲基化的内含子在开花植物中普遍存在，其潜在序列表现出动态进化。我们还在KYP中发现了广泛的遗传和表达变异，CMT3和IBM1跨越开花植株。我们鉴定了类似弱ibm1突变体的拟南芥和具有减少的IBM1表达或缺失的十字花科物种。在一些开花植物中，向IBM1活性降低的进化可以解释CMT3活性降低或丢失以及基因体DNA甲基化丢失的频繁自然发生。在拟南芥中的cmt3突变体减轻了IBM1的有害作用。
