Bioinformatic studies of the wheat glutaredoxin gene family and functional analysis of the ROXY1 orthologues

CC-type glutaredoxins comprise a large land plant-specific class of oxidoreductases. Previous research shows roles for two such proteins in developmental processes in Arabidopsis; ROXY1 mediates petal initiation and morphogenesis, and ROXY1 and ROXY2 are required for normal anther development. In the present work, the broader glutaredoxin family was investigated in hexaploid wheat with bioinformatic methods, revealing a large and multifunctional gene family. With a PCR based method, three wheat ROXY homeoalleles were isolated. Complementation analyses show that these three isoforms fully complemented the roxy1 mutation in Arabidopsis. Further, yeast two-hybrid experiments demonstrate that one such wheat ROXY protein interacts strongly with TGA3, an Arabidopsis TGA transcription factor previously shown to associate with ROXY1. Deletion analyses show that TaROXY-alpha 3 docks to a glutamine rich region of TGA3, a putative transcriptional activation domain. These results suggest a conserved molecular role of Arabidopsis and wheat ROXY proteins in inflorescence/spike development, most likely in the post-translational regulation of TGA proteins including HBP-1b (the wheat PERIANTHIA orthologue), which likely exerts also a developmental function by activating histone gene transcription in highly proliferating tissues such as the SAM and root tip