Molecular regulation of cytokinesis during plant development

Cell division is one key parameter of plant growth and development. In general, it consists of nuclear division (karyokinesis) followed by the division of the cytoplasm (cytokinesis). In proliferating cells, cells cycle between cell division and a phase where doubling of the genome occurs (interphase). This cell cycle is regulated by the orchestrated action of rather conserved genes and their activities are indispensible in making the next phase possible. Deregulation of the cell cycle may lead to hyperproliferation, tumour formation or cell death. The cytoskeleton and in particular the dynamic microtubules play an essential role during cell cycle. In plants, they form four distinct arrays. In interphase, the cortical microtubules array is involved in the alignment of cellulose microfibrills and cell expansion. At the onset of mitosis, the preprophase band defines the plane of cell division. In mitosis, the spindle separates chromosomes and during cytokinesis the phargmoplast directs vesicles with cell wall material to the equatorial plane to form the new cell wall. Microtubule-associated proteins (MAPs) are important regulators of the structure and dynamic of these microtubule assemblies. The objective of the project is to determine the molecular mechanisms regulating cytokinesis. In preparatory investigations we identified cytokinesis mutants (hyade and pleiade; Müller et al., 2002) in the model plant Arabidopsis thaliana, which hold great promises for this goal. The proposal is divided in three main tasks focusing on the molecular, cell biological and biochemical analyses of the HYADE and PLEIADE genes and gene products. The third part concentrates on the functional characterization of the PLEIADE/MAP65 gene family. Due to the molecular basis of the mutants and their homology to proteins of other eukaryotes, the results may lead to a fundamental understanding of the last steps during cell division. And although plants are thought to have developed a specific solution in separating their daughter cells, the basic mechanism of controlling this process may be proven to be similar.

Cell division is one key parameter of plant growth and development. In general, it consists of nuclear division (karyokinesis) followed by the division of the cytoplasm (cytokinesis). In proliferating cells, cells cycle between cell division and a phase where doubling of the genome occurs (interphase). This cell cycle is regulated by the orchestrated action of rather conserved genes and their activities are indispensible in making the next phase possible. Deregulation of the cell cycle may lead to hyperproliferation, tumour formation or cell death. The cytoskeleton and in particular the dynamic microtubules play an essential role during cell cycle. In plants, they form four distinct arrays. In interphase, the cortical microtubules array is involved in the alignment of cellulose microfibrills and cell expansion. At the onset of mitosis, the preprophase band defines the plane of cell division. In mitosis, the spindle separates chromosomes and during cytokinesis the phargmoplast directs vesicles with cell wall material to the equatorial plane to form the new cell wall. Microtubule-associated proteins (MAPs) are important regulators of the structure and dynamic of these microtubule assemblies. The objective of the project is to determine the molecular mechanisms regulating cytokinesis. In preparatory investigations we identified cytokinesis mutants (hyade and pleiade; Müller et al., 2002) in the model plant Arabidopsis thaliana, which hold great promises for this goal. The proposal is divided in three main tasks focusing on the molecular, cell biological and biochemical analyses of the HYADE and PLEIADE genes and gene products. The third part concentrates on the functional characterization of the PLEIADE/MAP65 gene family. Due to the molecular basis of the mutants and their homology to proteins of other eukaryotes, the results may lead to a fundamental understanding of the last steps during cell division. And although plants are thought to have developed a specific solution in separating their daughter cells, the basic mechanism of controlling this process may be proven to be similar.