The Stomata of the Katanin Mutants, fra2, lue1 and bot1

Abstract

Katanin, is a microtubule severing protein that orchestrates microtubule organization throughout the plant cell cycle. Taking into consideration the role of the microtubule cytoskeleton in the stomatal development, the Arabidopsis thaliana katanin mutants, fra2, lue1 and bot1 were studied to observe how the absence of function of/malfunction of katanin affects stomatal development. Katanin mutants are characterised by less mature stomata and more young stomata and meristemoids forming clusters. The size of the mature stomata differed from col-0, with the katanin mutants having shorter guard cells and pores as well as smaller pore aperture. In addition, a unique type of cell was observed in the fra2 mutant, the persistent guard mother cells (GMC’s), where the GMC persisted and did not divide symmetrically to form a stoma. Another rather significant observation was that the cell walls of some epidermal cells in the mutants appeared to be incomplete. As far as the cell wall matrix components distribution is concerned, callose did not display significant differences compared to col-0 while pectins and hemicelluloses were differentially dispersed. Microtubules in cytokinetic GMCs were long, bended and connected to the nuclei, while microtubule arrays in katanin mutant leaf epidermis were aberrant and stomatal complexes had astral microtubule arrays as it was observed in the wild type. In conclusion, the malfunction of katanin appears to affect the development of stomata in the epidermis of young leaves in Arabidopsis thaliana, affecting not only stomatal patterning, since the one-cell spacing rule was compromised, but also the morphology of the stomatal complexes. The cell wall-matrix appears altered in the katanin mutants, possibly affecting the function of the stomata since katanin mutant stomata had a reduced pore aperture.