2 NOVEL MYB HOMOLOGS WITH CHANGED EXPRESSION IN LATE EMBRYOGENESIS-DEFECTIVE ARABIDOPSIS MUTANTS

Two novel MYB genes (ATMYBR1 and ATMYBR2) were isolated from Arabidops is thaliana. Binding to a conserved MYB recognition sequence is demons trated for the ATMYBR1 protein. The expression of both genes is affect ed by the fus3, lec1 and abi3 mutations causing pleiotropic defects du ring late embryogenesis and seed maturation including the loss of dorm ancy and desiccation tolerance. The strong increase of the transcript levels of both MYB genes during very late stages of embryogenesis typi cally found in wild type is missing in the mutants. Furthermore, the e xpression of both MYB genes is developmentally regulated in vegetative tissues. The highly conserved repeats (R2 and R3) of the DNA binding MYB domain of both proteins represent chimeric structures combining fe atures typical of plant and animal derived proteins. This demonstrates the existence of a distinct subfamily of animal-like MYB factors in p lant genomes.