A Rosa canina WUSCHEL-related homeobox gene, RcWOX1, is involved in auxin-induced rhizoid formation.

Homeobox (HB) proteins are important transcription factors that regulate the developmental decisions of eukaryotes. WUSCHEL-related homeobox (WOX) transcription factors, known as a plant-specific HB family, play a key role in plant developmental processes. Our previous work has indicated that rhizoids are induced by auxin in rose (Rosa spp.), which acts as critical part of an efficient plant regeneration system. However, the function of WOX genes in auxin-induced rhizoid formation remains unclear. Here, we isolated and characterized a WUSCHEL-related homeobox gene from Rosa canina, RcWOX1, containing a typical homeodomain with 65 amino acid residues. Real-time reverse transcription PCR (qRT-PCR) analysis revealed that RcWOX1 was expressed in the whole process of callus formation and in the early stage of rhizoid formation. Moreover, its expression was induced by auxin treatment. In Arabidopsis transgenic lines expressing the RcWOX1pro::GUS and 35S::GFP-RcWOX1, RcWOX1 was specifically expressed in roots and localized to the nucleus. Overexpression of RcWOX1 in Arabidopsis increased lateral root density and induced upregulation of PIN1 and PIN7 genes. Therefore, we postulated that RcWOX1 is a functional transcription factor that plays an essential role in auxin-induced rhizoid formation.