DRMY1, a Myb-Like Protein, Regulates Cell Expansion and Seed Production in Arabidopsis Thaliana.

Plant organ development to a specific size and shape is controlled by cell proliferation and cell expansion. Here, we identify a novel Myb-like Arabidopsis gene, Development Related Myb-like1 (DRMY1), which controls cell expansion in both vegetative and reproductive organs. DRMY1 is strongly expressed in developing organs and its expression is reduced by ethylene while it is induced by ABA. DRMY1 has a Myb-like DNA-binding domain, which is predominantly localized in the nucleus and does not exhibit transcriptional activation activity. The loss-of-function T-DNA insertion mutant drmy1 shows reduced organ growth and cell expansion, which is associated with changes in the cell wall matrix polysaccharides. Interestingly, overexpression of DRMY1 in Arabidopsis does not lead to enhanced organ growth. Expression of genes involved in cell wall biosynthesis/remodeling, ribosome biogenesis and in ethylene and ABA signaling pathways is changed with the deficiency of DRMY1. Our results suggest that DRMY1 plays an essential role in organ development by regulating cell expansion either directly by affecting cell wall architecture and/or cytoplasmic growth or indirectly through the ethylene and/or ABA signaling pathways.