Towards the analysis of translational regulation during male meiosis and dissection of pollen development via mutants in cell cycle control factors in Arabidopsis thaliana

Abstract

My PhD thesis can be divided in the meiosis and mitosis part. In both of them, although they were focused on different elements of the cell cycle, I was using Arabidopsis thaliana pollen as a model system. The meiosis project was following up an experiment that revealed, by quantitative expression analysis, that the transcripts of several selected meiosis specific genes do not correlate with entry into meiosis, suggesting extensive translation control. To test this hypothesis, I have adapted a previously developed system by Halstead et al. (2015) to compare, by live cell imaging of meiosis, the mRNA levels with the accumulating levels of the respective proteins. The other aim of this project was to create a live imaging system for investigating translation control in plants in general. The mitosis project was succeeding the research of Barbara Gloecke and was based on cdka;1+/- and fbl17 +/- mutants. In both of those lines a portion of pollen stops developing before the second mitotic division. My work in this project started with an intention to untangle the network of genes involved in the pre-mitotic S-phase entry. Namely it was to check if one of the D-type cyclins plays a major role in this process. In my studies I checked double mutants of D-type cyclins and cdka;1+/- or fbl17 +/- in order to understand which of the combinations would show further enhancement of mitotic defects observed in the single mutants. For the rest of the project I used pollen coming from double mutants of e2fa-/- and cdka;1+/- with fbl17 +/-. Those double mutants are showing pollen that will fail to enter the first mitotic division and remain a single cell. This new class of pollen allowed me to study the developmental potential of grains that were lacking both gametes. It made it possible to check if those cells are able to: differentiate into a vegetative cell, create a pollen tube, guide it towards the ovule and if they are able to penetrate it.