Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2004
Publication Date: 11/19/2004
Citation: Wang, Y., Magnard, J., McCormick, S., Yang, M. 2004. Progression through Meiosis I and Meiosis II in Arabidopsis Anthers is Regulated by an A-type Cyclin Predominately Expressed in Prophase I. Plant Physiology 136:4127-4135. Interpretive Summary: We have characterized a mutant of Arabidopsis (tardy asynchronous meiosis, or tam for short) that goes through male meiosis slowly. We identified the gene and found that it encodes a cyclin. Cyclins are important for progression through the cell cycle. Because the mutant that we have is a single amino acid change and is temperature sensitive, it is only slowed, not stopped. This mutant will be useful to study meiosis, since in other organisms mutations in cyclins are often lethal.
Technical Abstract: Meiosis is often described as a special case of cell division since it differs from mitosis in having two nuclear divisions without an intervening S-phase. It will be of great interest to uncover what molecular mechanisms underlie these special features of meiosis. We previously reported that the tardy asynchronous meiosis (tam) mutant of Arabidopsis (Arabidopsis thaliana) is slower in cell cycle progression in male meiosis. Here we report that TAM encodes the A-type cyclin, CYCA1;2. The point mutation in tam replaced a conserved threonine with an isoleucine in the linker region between the 4 and 5 helices of the first cyclin fold. By studying the dynamics of a CYCA1;2-green fluorescent protein fusion protein under the control of the CYCA1;2 promoter, we found that the fusion protein was most abundant at pachytene, but was undetectable from late prophase I until telophase II. Nonetheless, cell cycle progression in tam was delayed in both pachytene and meiosis II. We conclude either that the CYCA1;2 produced in prophase I indirectly regulates meiosis II progression, or that a very low level of CYCA1;2 directly regulates meiosis II progression. Either of these scenarios is a deviation from the typical mode of action of mitotic cyclins in mitosis and meiosis I, in which each nuclear division is coupled with a peak of expression of mitotic cyclins.