561 / 2019-03-17 16:24:13

Mitosis and DNA replication events define the boundaries of transition zone in Arabidopsis thaliana root tip

root,Arabidopsis thaliana,root model,root zonation,transition zone,mitosis,DNA replication,image analysis

Growth and Development > Growth and Development

In the root tip along the central axis there are several zones with principally different cell growth dynamics: root apical meristem (RAM), transition zone and elongation zone. We have used iRoCS toolbox to annotate the root tip organization in three dimensions and created the 3D map of mitosis distribution [Lavrekha et al., Plant Journal, 2017]. We showed that cessation of cell divisions was not a random process with the protophloem, epidermis and cortex stopped dividing the first and procambium the last. On the next step, we used iRocs toolbox to analyze another cell cycle marker – DNA replication event. We observed that DNA replication domains in endodermis and cambium were larger then in epidermis and cortex. We show that cells undergo endoreduplication not only in epidermis and cortex (as presented in [Hayashi et al., Scientific reports, 2013]), but in all root tissues. In all tissues the final DNA replication event was observed about 150 mkm far from the final mitosis. With these observations we are able to define the transition zone as the distance between the final mitosis in the RAM till the final DNA replication event in the root tip. We developed a 3D model to study the root tip zonation with cell dynamics and simplast cell growth. The model supported the idea that root cells start growing fast together only after all of them endoreduplicated. The work was supported by the Russian Foundation for Basic Research (19-54-12013).