LZF1/SALT TOLERANCE HOMOLOG3, an Arabidopsis B-Box Protein Involved in Light-Dependent Development and Gene Expression, Undergoes COP1-Mediated Ubiquitination
LZF1/SALT TOLERANCE HOMOLOG3, an Arabidopsis B-Box Protein Involved in Light-Dependent Development and Gene Expression, Undergoes COP1-Mediated Ubiquitination
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DOI：
10.1105/tpc.108.061747
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发表时间：
2008-09-01
期刊：
影响因子：
11.6
通讯作者：
Holm, Magnus
中科院分区：
文献类型：
--
作者：
Datta, Sourav;Johansson, Henrik;Holm, Magnus
B-box蛋白在植物光信号传导中起着重要作用。在这里，我们鉴定了光调节锌指1/耐盐同源基因（STH3），这是一个B-box编码基因，与光信号的两个关键调节因子，伸长下胚轴l5 （HY5）和构成光形态基因1 （COP1）相互作用。在体内，STH3与HY5物理相互作用，在植物细胞中与COP1共表达时，STH3显示出依赖COP1的核斑点定位。T-DNA插入突变体sth3对高强度蓝光、红光和远红光不敏感，在短时间内下胚轴拉长。对sth3、sth2和hy5之间的双突变体的分析表明，它们具有部分重叠的功能。有趣的是，原生质体的功能分析表明，STH3可以单独激活转录，也可以通过G-box启动子元件与STH2一起激活转录。此外，sth3在黑暗条件下抑制cop1下胚轴表型以及在光照条件下抑制花青素积累。最后，COP1在体外使STH3泛素化，表明STH3受COP1调控。总之，我们已经确定STH3是光形态发生的积极调节因子，与STH2和HY5协同作用，同时也是cop1介导的泛素化的靶标。
B-box containing proteins play an important role in light signaling in plants. Here, we identify LIGHT-REGULATED ZINC FINGER1/SALT TOLERANCE HOMOLOG3 (STH3), a B-box encoding gene that genetically interacts with two key regulators of light signaling, ELONGATED HYPOCOTYL5 (HY5) and CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1). STH3 physically interacts with HY5 in vivo and shows a COP1-dependent localization to nuclear speckles when coexpressed with COP1 in plant cells. A T-DNA insertion mutant, sth3, is hyposensitive to high fluence blue, red, and far-red light and has elongated hypocotyls under short days. Analyses of double mutants between sth3, sth2, and hy5 suggest that they have partially overlapping functions. Interestingly, functional assays in protoplasts suggest that STH3 can activate transcription both independently and together with STH2 through the G-box promoter element. Furthermore, sth3 suppresses the cop1 hypocotyl phenotype in the dark as well as the anthocyanin accumulation in the light. Finally, COP1 ubiquitinates STH3 in vitro, suggesting that STH3 is regulated by COP1. In conclusion, we have identified STH3 as a positive regulator of photomorphogenesis acting in concert with STH2 and HY5, while also being a target of COP1-mediated ubiquitination.