Comparative proteomics of mitosis and meiosis in Saccharomyces cerevisiae

Precise and timely segregation of genetic material and conservation of ploidy are the two foremost requirements for survival of a eukaryotic organism. Two highly regulated cell division processes, namely mitosis and meiosis are central to achieve this objective. The modes of chromosome segregation are distinct in these two processes that generate progeny cells of equal ploidy and half the ploidy in mitosis and meiosis, respectively. Additionally, the nutritional requirement and intracellular processing of biological cue also differ in these two processes. From this, it can be envisaged that proteome of mitotic and meiotic cells will differ significantly. Therefore, identification of proteins that differ in their level of expression between mitosis and meiosis would further reveal the mechanistic detail of these processes. In the present study, we have investigated the protein expression profile of mitosis and meiosis by comparing proteome of budding yeast cultures arrested at mitotic metaphase and metaphase-I of meiosis using proteomic approach. Approximately 1000 and 2000 protein spots were visualized on 2-DE and 2D-DIGE gels respectively, out of which 14 protein spots were significant in 2-DE and 22 in 2D-DIGE (p<0.05). All the significant spots were reproducible in all biological replicates and followed the same trend. Identification of the proteins from these spots revealed that nine proteins were common in both 2-DE and 2D-DIGE. These proteins are found to be involved in various cellular processes and pathways such as cytoskeleton function and cytokinesis, carbon, nitrogen, lipid metabolism, general translation and protein folding. Among these, our further study with the cytoskeletal proteins reveals that, compared to mitosis, an up-regulation of actin cytoskeleton and its negative regulator occurs in meiosis.Mitosis and meiosis are two different types of cell division cycles with entirely different outcomes with definite biological implication for almost all eukaryotic species. In this work, we investigated, for the first time, the differential proteomic profile of Saccharomyces cerevisiae culture arrested at mitotic metaphase (M) and metaphase-I (MI) of meiosis using 2-DE and 2D-DIGE. Our findings of up-regulation of actin and its negative regulator cofilin during meiosis suggest that the rate of actin cytoskeleton turnover is more in meiosis and actin cytoskeleton may play more crucial role during meiosis compared to mitosis. Present study also suggests that actin cytoskeleton and its regulators accumulated during meiosis by forming stable protein structure even though the corresponding mRNAs are degraded as cells enter into meiosis. This is in accordance with recent studies in higher eukaryotes where actin cytoskeleton is found to play vital role during meiotic chromosome segregation. Information generated by this study is significant to reveal that even though a cell that, unlike mitosis, is metabolically inactive with no isotropic bulging of membranes as buds (in meiosis) can require more actin cytoskeleton presumably to support nuclear movements.