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United States Department of Agriculture

Agricultural Research Service

Title: The Arabidopsis Gene Tardy Asynchronous Meiosis Is Required for the Normal Pace and Synchrony of Cell Division During Male Meiosis

Authors
item Magnard, J - USDA/UCB PGEC
item Yang, M - USDA/UCB PGEC
item Chen, Y - USDA/UCB PGEC
item Leary, Michele - USDA/UCB PGEC
item McCormick, Sheila

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2001
Publication Date: November 1, 2001

Interpretive Summary: Pollen development occurs after synchronous cell divisions during meiosis. It is not clear how synchrony of male meiosis is achieved. We describe an Arabidopsis mutant, named tardy asynchronous meiosis (tam), that exhibits a phenotype of delayed and asynchronous cell divisions during male meiosis. Our results suggest that the TAM protein positively regulates cell cycle progression. We speculate that there is a signal that couples the normal pace of cell cycle progression with the synchrony of cell division during male meiosis.

Technical Abstract: Male meiosis in higher organisms features synchronous cell divisions in a large number of cells. It is not clear how this synchrony is achieved, nor is it known whether the synchrony is linked to the regulation of cell cycle progression. Here, we describe an Arabidopsis mutant, named tardy asynchronous meiosis (tam), that exhibits a phenotype of delayed and asynchronous cell divisions during male meiosis. In Arabidopsis, two nuclear divisions occur before simultaneous cytokinesis yields a tetrad of haploid cells. In tam, cell divisions are delayed, resulting in the formation of abnormal intermediates, most frequently dyad meiotic products, or in rare cases, dyad pollen (two gametophytes within one exine wall). Temperature-shift experiments showed that the percentage of the abnormal intermediates increased at 27°C. Analysis of tam and the tam/quartet1 double mutant showed that most of these abnormal intermediates could continue through the normal rounds of cell divisions and form functional pollen, though at a slower than normal pace. The asynchrony of cell division started at the G2/M transition, with cells entering metaphase at different time points, during both meiosis I and II. In addition, chromosome condensation defects and mis-segregation were sometimes observed in tam. These observations suggest that the TAM protein positively regulates cell cycle progression, perhaps by promoting the G2/M transition. We speculate that there is a signal, perhaps TAM, that couples the normal pace of cell cycle progression with the synchrony of cell division during male meiosis.

Last Modified: 11/28/2014
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