MYB80, a regulator of tapetal and pollen development, is functionally conserved in crops

The Arabidopsis AtMYB80 transcription factor (formerly AtMYB103) regulate genes essential for tapetal and pollen development. One of these genes, coding for an aspartic protease (UNDEAD), may control the timing of tapetal programmed cell death (PCD). In crop plants such as rice and wheat, abiotic stresses lead to abnormal tapetal development resulting in delayed PCD. Manipulation of AtMYB80 function has been used to develop a reversible male sterility system applicable to hybrid crop production. MYB80 homologs were cloned from wheat, rice, canola and cotton. The promoters of the homologs drove temporal and spatial expression patterns of the GUS reporter gene in the tapetum and microspores of Arabidopsis anthers identical to the AtMYB80 promoter. A short region is conserved in all five MYB80 promoters. The MYB80 homolog genes, driven by the AtMYB80 or their respective promoters, rescued the atmyb80 mutant, completely restoring male fertility. The canola MYB80 was fused to the EAR (ERF-associated amphiphilic repression) repressor and canola plants transgenic for the construct exhibited premature tapetal degradation and subsequent pollen abortion. The five MYB80 homologs all shared a 44 amino acid sequence immediately adjacent to the R2R3 domain which appears to be necessary for MYB80 function.