Nup96 and HOS1 are Mutually Stabilized and Gate CONSTANS Protein Level,Conferring Long-day Photoperiodic Flowering Regulation in Arabidopsis

　　作者：Zhiyuan Cheng, Xiaomei Zhang, Penghui Huang, Guowen Huang, Jinglong Zhu, Fulu Chen,Yuchen Miao, Liangyu Liu*, Yong-Fu Fu*, and Xu Wang*

　　影响因子：8.631

　　刊物名称： The Plant Cell

　　出版年份：December 2019

　　doi:10.1105/tpc.19.00661

　　Abstract

　　The nuclear pore complex profoundly affects the timing of flowering; however, the underlying mechanisms are poorly understood. Here, we report that Nucleoporin 96 ( Nup96 ) acts as a negative regulator of long-day photoperiodic flowering in Arabidopsis thaliana . Through multiple approaches, we identified the E3 ubiquitin ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE 1 (HOS1) and demonstrated its interaction in vivo with Nup96. Nup96 and HOS1 mainly localize and interact on the nuclear membrane. Loss of-function of Nup96 leads to destruction of HOS1 proteins without a change in their mRNA abundance, which results in over-accumulation of the key activator of long-day photoperiodic flowering, CONSTANS (CO) proteins, as previously reported in hos1 mutants. Unexpectedly, mutation of HOS1 strikingly diminishes Nup96 protein level, suggesting that Nup96 and HOS1 are mutually stabilized and thus form a novel repressive module that regulates CO protein turnover. Therefore, the nup96 and hos1 single and nup96 hos1 double mutants have highly similar early-flowering phenotypes and overlapping transcriptome changes. Together, this study reveals a repression mechanism in which the Nup96-HOS1 repressive module gates the level of CO proteins and thereby prevents precocious flowering in long-day conditions.