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[符宏勇/施臥虎] 阿拉伯芥去泛素化酵素OTU5藉修飾組蛋白促進主要開花抑制因子FLCMAF4MAF5之表現調控開花

Radjacommare et al., 2023  Int J Mol Sci

Arabidopsis OTU5 is a novel flowering suppressor. OTU5 acts, in an associated protein complex (OTU5c), in parallel with SWR1c- and HUB1/2-mediated pathways to epigenetically activate FLC clade repressors and suppress flowering. OTU5 primarily activates FLC and, to a lesser extent, MAF5, MAF4, and MAF1, which in turn suppress major flowering initiators FT and SOC1 to repress flowering. OTU5 is involved in increasing the deposition of the activating histone mark H3K36me3 and in the downregulation of the suppressive histone marks H3K27me3 and H3K9me2 as well as ubH2B on specific loci, such as FLC, MAF4, and MAF5. OTU5-mediated flowering suppression is distinct from the SWR1c-mediated pathway, which activates FLC-related repressors through H2A.Z deposition. OTU5 also acts independently of the HUB1/2-mediated pathway, which modulates genome-wide ubH2B levels and activates a distinct set of FLC-related repressors through distinct activating/repressive histone marks. OTU5 is, however, partially required for FLC-mediated flowering suppression in autonomous pathway mutants and FRIGIDA-Col.

親緣關係與受質專一性分析結果,顯示阿拉伯芥OTU去泛素化酵素家族成員參與演化保守或植物專一性功能。otu5-1 突變株具早開花等多重性狀,與負責H2A.Z 置換之SWR1蛋白複體 (SWR1c)次單元(例如ARP6)突變株系之性狀十分類似。轉錄基因組及RT-qPCR 分析結果顯示 FLC 及MAF4-5 表現下降應係 otu5-1早開花之主要因素。qChIP 分析顯示otu5-1突變株其FLCMAF4-5基因座上之激活及抑制組蛋白修飾分別降低或增加。生化層析、GFP融合蛋白瞬時表現、以及MNase 細胞核處理分析顯示OTU5大量表現於細胞核內並與染色絲結合。qChIP 分析更顯示OTU5 可與 FLC 及 MAF4-5基因座結合。OTU5可以蛋白複體型式表現,但由於在arp6-1 突變株中 OTU5複體之分子量不變,該複體顯然不同於SWR1c。此外,otu5-1 arp6-1 雙突變株明顯具增效性狀,而且H2A.Z 含量在FLC/MAF4-5基因座僅於arp6-1突變株中下降而在otu5-1突變株中並未改變。所有結果顯示阿拉伯芥OTU5係一嶄新開花抑制因子,其作用應獨立於SWR1c-仲介之 機制,藉修飾組蛋白促進主要開花抑制因子FLCMAF4MAF5表現而抑制開花。雙突變遺傳分析也顯示OTU5其作用應獨立於HUB1-仲介之 機制。不過,雙突變遺傳分析也顯示在開花自發途徑組成因子突變(autonomous pathway mutants)以及FRIGDA所造成之FLC-仲介之晚開花機制中,卻有部分功能需要OTU5的參與。

Radjacommare et al., 2023 The Arabidopsis deubiquitylase OTU5 suppresses flowering by histone modification-mediated activation of the major flowering repressors FLC, MAF4, and MAF5Int J Mol Sci 24 (7), 6176, 2023-03-24.

Link: https://www.mdpi.com/1422-0067/24/7/6176