Analysis Of Microsporogenesis And Embryonic Development In Arabidopsis Mutant Tam-t

CYCA1; 2 encoding by TAM (Tardy Asynchronous Meiosis) gene is an important cell cycle regulators of the Arabidopsis microsporogenesis. The substitution of a hydrophobic Ile for a hydrophilic Thr presumably results in incorrect folding of the a4 and a5 helices, which likely leads to a loss of function of CYCA1;2. This interpretation is consistent with the temperature-sensitivity of the tam mutation. 27℃for 24 hours or more, cytokinesis in tam meiosis is superficially similar to successive cytokinesis because dyads are first formed after meiosis I. Each dyad can divide again to form spores, and each spore, when released from the callose wall. Cell cycle progression in tam was delayed in both pachytene and meiosis II, leading to pollen development desynchronized (Magnard et al, 2001; Wang et al. 2004) .In this study, we show that Arabidopsis tam-t mutants exhibits severe reduction in fertility. The length of the tam-t mutant silique is smaller than that in wild type, accordingly the seed-set of tam-t mutant is only 20% of that in wild type. When mutants grow at room temperature, we find that dyads are first formed after meiosis I. When meiosis II occurred, the asynchrony returned. In most of the dyads, cell division was more advanced in one of the cells. In embryogenesis we found abnormal embryo in the octant stage, desynchronization of cell division when embryos develop from octant stage to dermatogens stage, abnormal cell division at early globular embryo and abortion of embryos. Taken together, TAM is very important during sexual reproduction in Arabidopsis thaliana.