阿拉伯芥組蛋白去甲基化酶JMJ28對開花調控之功能研究

Abstract

JmjC 組蛋白去甲基化酶廣泛地存在於植物、真菌和動物當中。阿拉伯芥的21種JmjC組蛋白去甲基化酶會依其序列相似性被分為5個類型。在先前報導中，阿拉伯芥中JmjC家族成員參與在DNA甲基化、siRNA產生、開花時間、brassinosteroid訊息傳遞及植物生理週期調控中。在本研究中我們發現，屬於 KDM3/JHDM2 類的 JmjC 組蛋白去甲基化酶 JMJ28具有專一性去除組蛋白H3離胺酸9上二甲基及三甲基（H3K9Me2/Me3）的活性，並且會和組蛋白去乙醯化酶 HDA6 有交互作用。jmj28突變株有晚開花的表型，透過檢測jmj28突變株與野生型植株中的基因表現，我們發現調控開花的自主途徑中的FPA與FCA以及光週期途徑中的GI與CO的基因表現，相對於野生型在突變株中皆有降低。從這些結果我們推測，JMJ28可能會藉由其本身的組蛋白去甲基化酶活性促進阿拉伯芥自發性調控路徑中的FCA基因表現，來調控阿拉伯芥的開花時間。

JmjC domain-containing demethylases are conserved evolutionarily in plants, yeast and humans. In Arabidopsis, 21 jmjC domain-containing demethylases are divided into 5 distinct groups according to sequence similarities. Previous studies indicated that JmjC domain-containing demethylases are involved in the regulation of gene expression associated with DNA methylation, siRNA regeneration, flowering-time control, brassinosteroid signaling and circadian clock regulation. In this study, we showed that JMJ28, a member of KDM3/JHDM2 group, interacts with the histone deacetylase HDA6. Furthermore, JMJ28 has demethylase activity specific to H3K9me2 and H3K9me3. In addition, the JMJ28 T-DNA insertion knockout mutants, jmj28-1 and jmj28-2, have a late flowering phenotype under both long day and short day conditions. The expression of the autonomous pathway genes FPA and FCA as well as the photoperiod pathway genes GI, CO and FT are decreased in jmj28 mutants compared to wild type. In addition, the expression of FLC, MAF4 and MAF5 are also increased in jmj28 mutants compared to wild type. Furthermore, JMJ28 may activate the autonomous genes FCA through H3K9me3 demethylation in flowering time control.