Plant biology

Nuclear Glutaredoxin Promotes Petals

Science Signaling  24 Feb 2009:
Vol. 2, Issue 59, pp. ec73
DOI: 10.1126/scisignal.259ec73

ROXY1 is a CC-type plant glutaredoxin, a class of glutathione-dependent oxidoreductases. In roxy1 mutant Arabidopsis plants, fewer petals than normal form. In contrast, plants with mutations in the PERIANTHIA (PAN) gene form extra petals. With this background, Li et al. found that these two proteins worked together to control petal development. A yellow fluorescent protein (YFP) fusion with ROXY1 showed both cytosolic and nuclear distribution and rescued the petal formation defect in roxy1 mutant plants. However, forced nuclear targeting of the fusion protein showed that only nuclear ROXY1 was required for rescue of the petal formation defect. In a yeast two-hybrid screen, ROXY1 interacted with several members of the TGA family of transcription factors, including PAN. These interactions were confirmed in plants using a bimolecular fluorescence assay. The domain of ROXY1 required for interaction with the TGA proteins was mapped by deletion analysis and, when expressed in roxy1 mutant plants, only those capable of interacting with TGA proteins complemented the mutant. TGA2 and PAN were coexpressed in cells of the floral organ primordia that also express ROXY1. Roxy1, pan double mutants exhibited the same phenotype of increased petals as did the pan single mutants, which suggests that ROXY1 is upstream of PAN. By examining the ability of PAN mutants in which each cysteine residue was individually mutated to serine to complement the pan mutant, the authors demonstrated that Cys340, which is in a conserved region that may function as a transactivation domain, was required for PAN activity. The authors thus propose that ROXY1 may posttranslationally modify PAN at Cys340 to inhibit its activity and thus control the number of petals formed.

S. Li, A. Lauri, M. Ziemann, A. Busch, M. Bhave, S. Zachgo, Nuclear activity of ROXY1, a glutaredoxin interacting with TGA factors, is required for petal development in Arabidopsis thaliana. Plant Cell preview, published 13 February 2009 as 10.1105/tpc.108.064477. [PubMed]