Characterization of the OFP Gene Family and its Putative Involvement of Tuberous Root Shape in Radish.

The shape of the tuberous root, a very important quality trait, varies dramatically among radish cultivars. Ovate family proteins (OFPs) are plant-specific proteins that regulate multiple aspects of plant growth and development. To investigate the possible role of OFPs in radish tuberous root formation, 35 putative RsOFPs were identified from radish, and their expression patterns were detected during tuberous root development in six different radish cultivars. Phylogenetically, RsOFP2.3 clustered together with AtOFP1 and other members of this family that are known to regulate organ shape. Moreover, RsOFP2.3 expression was negatively correlated with tuberous root elongation after the cortex splitting stage, which made this gene the top candidate for the involvement of tuberous root shape. To further characterize the function of RsOFP2.3, it was ectopically expressed in Arabidopsis. RsOFP2.3 overexpression in Arabidopsis led to multiple phenotypical changes, especially the decreased length and increased width of the hypocotyl. Furthermore, RsOFP2.3 expression was induced by all the five classic plant hormones except ethylene, and it was most sensitive to exogenous gibberellic acid treatment. We also found that RsOFP2.3 was localized in the cytoplasm. Taken together, our results suggested the possible involvement for RsOFP2.3 in suppressing radish tuberous root elongation and that it encodes a functional protein which mainly inhibits the elongation of Arabidopsis aerial organs.