Nuclear Activity of ROXY1, a Glutaredoxin Interacting with TGA Factors, Is Required for Petal Development inArabidopsis thaliana 

Abstract

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.

Arabidopsis Basic Leucine-Zipper Transcription Factors TGA9 and TGA10 Interact with Floral Glutaredoxins ROXY1 and ROXY2 and Are Redundantly Required for Anther Development

“…One of two regulatory Cys residues in TGA1 is conserved in PAN and required for activity (Li et al, 2009). Modification of this residue is proposed to depend on the activity of ROXY1, a CC-type glutaredoxin that interacts with PAN in plant cell nuclei (Li et al, 2009).…”

“…One of two regulatory Cys residues in TGA1 is conserved in PAN and required for activity (Li et al, 2009). Modification of this residue is proposed to depend on the activity of ROXY1, a CC-type glutaredoxin that interacts with PAN in plant cell nuclei (Li et al, 2009). roxy1 mutants initiate fewer petals than the wild type and later petal morphogenesis can be aberrant, indicating that ROXY1 is a regulator of PAN (Xing et al, 2005;Li et al, 2009).…”

Interplay between the NADP-Linked Thioredoxin and Glutathione Systems in Arabidopsis Auxin Signaling

“…Two closely related CC-type glutaredoxin proteins (ROXY1 and ROXY2) were recently shown to act in flower development (Xing et al, 2005;Xing and Zachgo, 2008;Li et al, 2009). Flowers develop in these plants, but the roxy1 mutant exhibits abnormalities during petal development, while the roxy1 roxy2 double mutant shows additional anther development perturbation.…”

“…In a few reports, TRXs have been shown to be involved in pathogenic responses (Rivas et al, 2004;Sweat and Wolpert, 2007;Tada et al, 2008), hypersensitiviy to oxidants (Broin et al, 2000(Broin et al, , 2002Broin and Rey, 2003), cytochrome b(6)f biosynthesis (Lennartz et al, 2001), and plasmodesmal transport in meristems (Benitez-Alfonso et al, 2009). Recently, genetic evidence has revealed functions of GRX-like proteins in flower development (Xing et al, 2005;Xing and Zachgo, 2008;Li et al, 2009).…”

Sporisorium reilianumInfection Changes Inflorescence and Branching Architectures of Maize

“…Therefore, it is possible that the morphological changes induced by S. reilianum colonization of the inflorescence are an indirect result of the increased ROS levels in the plant cells. Possibly, this indirect effect is exerted via redox regulation of glutaredoxins, which have recently been shown to play a crucial role in floral organ development (Xing and Zachgo, 2008;Li et al, 2009aLi et al, , 2009b. On the other hand, the increased ROS levels in infected floral tissues might be a result of the down-regulation of a specific MADS box transcription factor.…”