The maize mutant polymitotic affects cell cycle events during microspore development

The maize (Zea mays L.) male-sterile mutant polymitotic (po) was analyzed u tilizing in-vitro cell culture and immunocytochemistry methods to better un derstand the relationship between the mutant phenotype and cell cycle event s during microspore development. Using a live meiocyte culture system, init iation and progression through abnormal post-meiotic cell cycles at the end of meiosis II was documented in the po mutant with a CCD camera and a comp uter image analysis system. Our results showed that premature chromosomal c ondensation precedes abnormal postmeiotic cell cycle progression in the go mutant at the end of meiosis II. Temporal analysis of the po mutant in-vitr o revealed that unsynchronized post-meiotic divisions occurred immediately following the end of meiosis II and did not require interaction with the su rrounding somatic tissue. Furthermore, the altered distribution of p34(cdc2 ) protein kinase from a nuclear to a cytoplasmic location was identified in tetrads during onset of the unsynchronized divisions in the po mutant. In contrast, a predominantly nuclear location of p34(cdc2) was observed during interphase of the wild-type tetrads at the same stage.