OsMYB103 is required for rice anther development by regulating tapetum development and exine formation

The Arabidopsis AtMYB103 gene is required for anther development, but whether the homologous gene in rice has the same role is unclear. Sequence analysis indicated that the rice OsMYB103 gene shares a high sequence similarity with AtMYB103. Therefore, we investigated the functional role of OsMYB103 in anther development using an RNAi approach. The OsMYB103 RNA transcript was expressed most abundantly in flowers, specifically in the tapetum, premeiotic pollen mother cells, and meiotic PMCs. OsMYB103-RNAi transgenic lines grew normally during their vegetative phase but displayed reduced male fertility, a phenotype that was associated with downregulated OsMYB103 transcript levels. Expression of OsMS2, an ortholog of the Arabidopsis AtMS2 gene, was also dramatically reduced in the transgenic plants. Knockdown of OsMYB103 led to defects in tapetum development, and most of the microspores in mature anthers lacked exines. Moreover, OsMYB103 could partially rescue the male sterility phenotype of an AtMYB103 knockout mutant ms188. Taken together, these results indicate that OsMYB103 does have an important role in rice tapetum and microspore development.