meiotin-1 gene expression in normal anthers and in anthers exhibiting prematurely condensed chromosomes

We have cloned and sequenced the promoter of a meiotin-1 gene, and have determined the precise temporal and spatial pattern of meiotin-1 gene expression. The expression of the meiotin-1 gene is controlled in two increments. The meiotin-1 gene is not expressed in any of the vegetative tissues examined. Early in microsporogenesis, low levels of meiotin-1 RNA can be detected. At the onset of meiosis, there is a dramatic increase in meiotin-1 RNA levels in both tapetal and meiotic cells. However, while meiotin-1 RNA is observed in both the nucleus and cytoplasm of meiotic cells, it is found only in the nucleus of the tapetal cells. We have also examined the expression of the meiotin-1 gene in aberrant meiotic nuclei that prematurely condense their chromosomes; these nuclei have reduced levels of the meiotin-1 protein. The aberrant nuclei have only the basal level of meiotin-1 RNA; they do not exhibit the transcriptional induction seen for normal cells at the onset of meiosis. Implications for the function of meiotin-1 in regulating chromatin condensation, and in coordinating meiotic and tapetal cell activities are discussed.