Abstract
While molecular mechanisms underlying axis formation and organ initiation have started to emerge, our knowledge on the mechanism controlling early embryogenesis is still limited. By using a root-specific activation tagging system of Arabidopsis, we have revealed that members of the RKD family of plant-specific putative transcription factors possess an ability to promote cell division and de-differentiation. Reporter analyses indicated that all five members of the Arabidopsis RKD family are transcribed at small domains in early embryos, though, only mutants of RKD4 showed abnormal cell division in early embryos. GFP-tagged RKD4 proteins localized to the nuclei and the amino-terminal region of RKD4 activated gene transcription in yeasts, supporting the notion that RKDs function as transcription factors. Induced ectopic expression of RKD4 in the seedlings activated expression of early embryo-specific genes, and some of them were down-regulated in rkd4 mutants. Taken together, these results suggest that RKD proteins regulate gene expression in early embryos, and whereby promote their correct development.
