부산대학교 도서관

Heavy-ion beams have been applied as effective mutagens to various plant materials. Pollen has been used as material for mutant induction and genetic analysis. However, our knowledge of the DNA damage response of plant male gametes remains limited. In the present study, we irradiated Cyrtanthus mackenii pollen with an argon ion beam, which induced complex DNA damage, and investigated the DNA damage response of male gametes during pollen tube growth. Male gametes derived from the irradiated pollen grains were isolated from pollen tubes after 12 and 24 h of culture and subjected to cell cycle analysis. After 12 h of culture, the irradiated generative cells were frequently arrested at metaphase during pollen mitosis II (PMII), and the proportion of metaphase cells increased with increasing absorbed dose. These results suggest that the genomic lesions induced by the argon ion beam caused spindle assembly checkpoint (SAC)-dependent arrest. After 24 h of culture, the irradiated male gametes completed PMII, albeit forming sperm cells with abnormalities in chromosome separation, and chromosomal bridges were often formed between these cells. Moreover, phosphorylated H2AX foci, an indicator of DNA double-strand breaks, were detected in the irradiated male gametes after 24 h of culture, regardless of passing through the SAC. Taken together, these results indicate that male gametes activate functions to cope with radiation-induced complex DNA damage during pollen tube growth.