Cytological Analysis of Male-Sterile MS5 Japanese Cedar (Cryptomeria japonica D. Don) and Comparison with Other Male-Sterile Mutants

Abstract

Cryptomeria japonica D. Don is a model plant for studying male sterility in conifers. To date, five male sterile loci have been identified by crossing tests. When at least one of these loci is homozygote of a recessive male sterile allele, male sterility is induced. Cytological studies have been performed for ms1 to ms4 mutants, but there have yet to be such investigations of ms5 mutants. This study newly showed that ms2 mutants lack callose and exhibit different phenotypes for each microsporangium. Furthermore, we found the leakage of cellular contents and the appearance of amorphous substances in ms3 mutants. We also detected leakage of cellular contents in ms4 mutants. On the other hand, abnormal pollen development in ms5 mutants was found to begin at the tetrad stage. This abnormality was characterized by the maintenance of abnormal tetrads and uneven spores, abnormal pollen wall formation, covered with amorphous substances, disappearance of the nucleus, and central nuclear positioning during the binuclear microspore stage. These results were clearly different from those of ms1 to ms4 mutants. Abnormal meiosis in pollen mother cells, the abnormal pollen wall, and abnormal mitosis during pollen development may be closely associated with male sterility caused by mutation of MS5.