CDM1 is required for meiotic progression and genome integrity during male meiosis in Arabidopsis

Microsporogenesis involves the integration of meiosis with the developmental program leading to formation of microspores from meiocytes. The CALLOSE DEFICIENT MICROSPORE 1 ( CDM1 ) gene of Arabidopsis has been previously characterized as being required for callose metabolism and its loss results in defects in microspore wall development, degeneration of meiotic products, and male sterility. We report here that CDM1 is required for normal meiosis I progression, meiotic chromosome organization, and maintenance of DNA integrity. CDM1 is part of the ATM dependent DNA damage response in dividing vegetative tissues. The cdm1 mutant shows defects in meiotic chromosome condensation, arrest at metaphase I, susceptibility to chromosome breakage in rDNA regions, defects in positioning of the products of meiosis, and increased expression of recombination related genes. However, fidelity of chromosome segregation is not affected. Furthermore, the meiotic phenotype of cdm1 is independent of SPO11 induced meiotic double strand breaks. CDM1 protein displays granular localization in meiosis throughout the cytoplasm that resembles that of mRNP granules. The results show that CDM1 is required for maintenance of proper chromosome organization and DNA integrity in the course of male meiosis. The chromosomal defects in cdm1 may originate from regions of defective or incomplete replication.