INVESTIGATING EARLY SIGNS OF ENDOREDUPLICATION IN ARABIDOPSIS SHOOT: AN UNKNOWN FACT

Abstract

Endoreduplication is alternative form of cell cycle that involves the replication of DNA without mitosis. It commonly occurs in various tissues of plants like pavement cells of leaf, trichomes and sepals of flower and led to increase in size of the cell. Shoot apical meristem (SAM) is a region from where the aboveground organs of the plant arise. The cells in the meristem remain in meristematic state (mitotic) and get displaced from there to form the differentiated tissues. But how the nuclear DNA synthesis vary from the meristematic cells to the differentiated tissues is not very well studied. It has been observed through the present study that the cells in shoot tip of Arabidopsis are diploid in nature and starts to endoreduplicate at 1cm away from the shoot, down the stem which was justified by the flow cytometer-based DNA analysis of different Arabidopsis tissues. Petal is known to be the most variable part of the flower with different color, shape, size and fragrance but little is known about its characterization. The cell identities in petal are diverse with different cell types. One is small sized distal cells and the other is large sized proximal cells. The present study has addressed that the large size of proximal cells of petal is not merely a cell expansion but is something related to endoreduplication. This was evidenced by the DNA estimation of FACS (Florescent activated cell sorter) sorted petal cells of Arabidopsis. This is the first study in which SAM, stem, leaf and petal cells are taken into account for ploidy analysis by flow cytometry. In shoot apex we did not see endoreduplication however as the cells descend towards the stem or leaf they enter into differentiation pathways and undergo endoreduplication. On the other hand, different ploidies in petal cells shows the signs of endoreduplication which can be a way towards differentiation.