Tapetum development and meiosis play crucial roles in anther development. Here we identified a rice gene, DEFECTIVE TAPETUM AND MEIOCYTES 1 (
DTM1), which controls the early stages of that development. This gene encodes for an endoplasmic reticulum (ER)
membrane protein that is present only in cereals. Our
T-DNA insertion mutations gave rise to abnormal tapetal formation. Cellular organelles, especially the ER, were underdeveloped, which led to hampered differentiation and degeneration of the tapetum. In addition, the development of pollen mother cells was arrested at the early stages of meiotic prophase I.
RNA in-situ hybridization analyses showed that
DTM1 transcripts were most abundant in tapetal cells at stages 6 and 7, and moderately in the pollen mother cells and meiocytes. Transcripts of UDT1, which functions in tapetum development during early meiosis, were reduced in
dtm1 anthers, as were those of PAIR1, which is involved in chromosome pairing and synapsis during meiosis. However, expression of
MSP1 and MEL1, which function in anther wall specification and germ cell division, respectively, was not altered in the
dtm1 mutant. Moreover, transcripts of
DTM1 were reduced in
msp1 mutant anthers, but not in udt1 and pair1 mutants. These results, together with their mutant phenotypes, suggest that
DTM1 plays important roles in the ER membrane during early tapetum development, functioning after
MSP1 and before UDT1, and also in meiocyte development, after MEL1 and before PAIR1.