Li Shutian, Lauri Andrea, Ziemann Mark, Busch Andrea, Bhave Mrinal, Zachgo Sabine
Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany.
Plant Cell. 2009 Feb;21(2):429-41. doi: 10.1105/tpc.108.064477. Epub 2009 Feb 13.
Glutaredoxins (GRXs) have thus far been associated mainly with redox-regulated processes participating in stress responses. However, ROXY1, encoding a GRX, has recently been shown to regulate petal primorida initiation and further petal morphogenesis in Arabidopsis thaliana. ROXY1 belongs to a land plant-specific class of GRXs that has a CC-type active site motif, which deviates from ubiquitously occurring CPYC and CGFS GRXs. Expression studies of yellow fluorescent protein-ROXY1 fusion genes driven by the cauliflower mosaic virus 35S promoter reveal a nucleocytoplasmic distribution of ROXY1. We demonstrate that nuclear localization of ROXY1 is indispensable and thus crucial for its activity in flower development. Yeast two-hybrid screens identified TGA transcription factors as interacting proteins, which was confirmed by bimolecular fluorescence complementation experiments showing their nuclear interaction in planta. Overlapping expression patterns of ROXY1 and TGA genes during flower development demonstrate that ROXY1/TGA protein interactions can occur in vivo and support their biological relevance in petal development. Deletion analysis of ROXY1 demonstrates the importance of the C terminus for its functionality and for mediating ROXY1/TGA protein interactions. Phenotypic analysis of the roxy1-2 pan double mutant and an engineered chimeric repressor mutant from PERIANTHIA (PAN), a floral TGA gene, supports a dual role of ROXY1 in petal development. Together, our results show that the ROXY1 protein functions in the nucleus, likely by modifying PAN posttranslationally and thereby regulating its activity in petal primordia initiation. Additionally, ROXY1 affects later petal morphogenesis, probably by modulating other TGA factors that might act redundantly during differentiation of second whorl organs.
到目前为止，谷氧还蛋白（GRXs）主要与参与应激反应的氧化还原调节过程相关。然而，最近研究表明，编码GRX的ROXY1在拟南芥中可调控花瓣原基起始及后续花瓣形态建成。ROXY1属于陆地植物特有的一类GRX，具有CC型活性位点基序，这与普遍存在的CPYC和CGFS型GRX不同。对由花椰菜花叶病毒35S启动子驱动的黄色荧光蛋白-ROXY1融合基因的表达研究显示，ROXY1呈核质分布。我们证明ROXY1的核定位是必不可少的，因此对其在花发育中的活性至关重要。酵母双杂交筛选鉴定出TGA转录因子为相互作用蛋白，双分子荧光互补实验证实了它们在植物体内的核相互作用。ROXY1和TGA基因在花发育过程中的重叠表达模式表明，ROXY1/TGA蛋白相互作用可在体内发生，并支持它们在花瓣发育中的生物学相关性。ROXY1的缺失分析表明C末端对其功能以及介导ROXY1/TGA蛋白相互作用的重要性。roxy1-2 pan双突变体和来自花TGA基因PERIANTHIA（PAN）的工程化嵌合阻遏物突变体的表型分析支持了ROXY1在花瓣发育中的双重作用。总之，我们的结果表明，ROXY1蛋白在细胞核中发挥作用，可能是通过对PAN进行翻译后修饰，从而调节其在花瓣原基起始中的活性。此外，ROXY1可能通过调节其他在第二轮器官分化过程中可能起冗余作用的TGA因子来影响后期花瓣形态建成。
