AUTHOR=Lim Chae Jin , Park Ki Suk , Ali Akhtar , Park Junghoon , Ryou Seung Min , Shen Mingzhe , Khan Haris Ali , Bader Zein Eddin , Zareen Shah , Bae Min Jae , Choi Jong Hyoo , Xu Zheng-Yi , Pardo Jose M. , Yun Dae-Jin 

TITLE=Negative regulation of floral transition in Arabidopsis by HOS15-PWR-HDA9 complex

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1105988

DOI=10.3389/fpls.2022.1105988

ISSN=1664-462X

ABSTRACT=<p>Arabidopsis HOS15/PWR/HDA9 repressor complex, which is similar to the TBL1/NcoR1/HDAC complex in animals, plays a well-known role in epigenetic regulation. PWR and HDA9 have been reported to interact with each other and modulate the flowering time by repressing <italic>AGL19</italic> expression, whereas HOS15 and HDA9, together with the photoperiodic evening complex, regulate flowering time through repression of GI transcription. However, the role of the HOS15/PWR/HDA9 core repressor complex as a functional unit in the regulation of flowering time is yet to be explored. In this study, we reported that the loss-of-function <italic>hos15-2/pwr/hda9</italic> triple mutant accumulates higher transcript levels of <italic>AGL19</italic> and exhibits an early flowering phenotype similar to those of <italic>hos15</italic>, <italic>pwr</italic>, and <italic>hda9</italic> single mutants. Interestingly, the accumulation of HOS15 in the nucleus was drastically reduced in <italic>pwr</italic> and <italic>hda9</italic> mutants. As a result, HOS15 could not perform its role in histone deacetylation or interaction with H3 in the nucleus. Furthermore, HOS15 is also associated with the same region of the <italic>AGL19</italic> promoter known for PWR-HDA9 binding. The acetylation level of the <italic>AGL19</italic> promoter was increased in the <italic>hos15-2</italic> mutant, similar to the <italic>pwr</italic> and <italic>hda9</italic> mutants. Therefore, our findings reveal that the HOS15/PWR/HDA9 repressor complex deacetylates the promoter region of <italic>AGL19</italic>, thereby negatively regulating <italic>AGL19</italic> transcription, which leads to early flowering in Arabidopsis.</p>