Defective Microspore Development 1 is required for microspore cell integrity and pollen wall formation in rice

Highly coordinated pollen wall patterning is essential for male reproductive development. Here, we report the identification ofDefective Microspore Development 1(DMD1), which encodes a nuclear-localized protein possessing transactivation activity.DMD1is preferentially expressed in the tapetum and microspores during post-meiotic development. Mutations inDMD1cause a male-sterile phenotype with impaired microspore cell integrity. The mutants display abnormal callose degradation, accompanied by inhibited primexine thickening in the newly released microspores. Several genes associated with callose degradation and primexine formation are downregulated indmd1anthers. In addition, irregular Ubisch body morphology and discontinuous endexine occur, and the baculum is completely absent indmd1. DMD1 interacts with Tapetum Degeneration Retardation (TDR), a basic helix-loop-helix transcription factor required for exine formation. Taken together, our results suggest thatDMD1is responsible for microspore cell integrity, primexine formation and exine pattern formation duringOryza sativa(rice) microspore development.