Impacts of KATANIN loss-of-function on growth and development in Arabidopsis thaliana

Microtubules are one of key structures in the plant cell. They are involved in the process of cell division as well in as guiding the cellulose synthase complex, which is responsible for cellulose deposition in the new cell wall layer. Microtubules are dynamic; their orientations can be quickly changed and are important in guiding cell growth direction. KATANIN is an important player in regulating microtubule dynamics, and its loss-of-function mutants have been used widely to study the roles of microtubules in plants. For instances, they have been used to study how microtubule dynamics contribute to the development of various organs, such as the shoot apical meristem, the flower and the root. However, a quantitative and comprehensive analysis of how KATANIN contributes to different aspects of organ development such as cell division and cell growth over many days is still lacking. In this study, I characterized the impacts of KATANIN loss-of-function on the development of the sepal, an organ frequently used in recent years as a model for organogenesis. The impacts on cell division rates and dynamics, on cell growth rates and growth arrest dynamics, on directions of growth were investigated. The results show that loss of KATANIN leads to reduced cell division rates, reduced growth anisotropy and more diverged cell growth angles, which collectively contribute to the wider shape of the mutant mature sepal. In contrast, KATANIN is not required for several other developmental aspects, such as average cell growth rate, and the dynamics of growth front and cell division front.