AMEIOTIC, A GENE THAT CONTROLS MEIOTIC CHROMOSOME AND CYTOSKELETAL BEHAVIOR IN MAIZE

Microtubule organization during the novel cell division of ameiotic microsporocytes was examined using indirect immunofluorescence microscopy. A recessive mutation of the maize gene Ameiotic causes the replacement of meiosis I with a synchronized mitotic division (Palmer, R. G. (1971). Chromosoma 35, 233-246). All identifiable cytological features of this division, including chromosome behavior and microtubule organization, were typical of somatic cell division. Significantly, a cortical microtubule band was observed during prophase in ameiotic cells. In most somatic plant cells, a preprophase band of microtubules (PPB) predicts the cortical site where the future cell plate will join the sidewall. Similar structures, however, are absent in all meiotic and postmeiotic reproductive cells examined to date. These disruptions are consistent with a model where the wild-type Ameiotic gene encodes a product which acts during or before G2 and is necessary for initiating several independent meiotic processes, including both meiotic chromosome behavior and microtubule organization. The ameiotic mutation provides additional evidence that aspects of cytoskeletal organization unique to meiosis are genetically controlled. Finally, the presence of a PPB during the ameiotic division supports a model whereby multiple mechanisms are used to determine and maintain division plane polarity during normal meiosis. © 1992.