J. Lucas, J. Nadeau, F. Sack

Dept. Plant Biology, Ohio State University

Microtubules appear to play various roles in stomatal development. Stomata originate from highly regulated asymmetric and symmetric cell divisions. In Arabidopsis, the first asymmetric division yields two unequal cells, the smaller of which is the meristemoid. After a series of 0-3 asymmetric divisions, the meristemoid gives rise to the guard mother cell (GMC). An equal division of the GMC produces the two guard cells. The location of both types of divisions is predicted by a preprophase band of cortical microtubules. In addition, the GMC is unique in having wall thickenings that mark the division site. Guard cell morphogenesis also involves characteristic microtubular arrays such as anticlinally arranged microtubules along the developing pore wall, and radial arrays that parallel the distinct arrangement of cellulose in the kidney-shaped guard cell. Previous studies of microtubules during stomatal development have imaged fixed material, and little is known about intermediate stages of development. We are conducting an intensive study of microtubular arrangement during wild type stomatal development in living cells using a transgenic line with an alpha-tubulin::GFP fusion that is viewed by fluorescence microscopy including deconvolution. Our goal is to further define and understand the stages of development of each type of precursor cell, of the guard cell, and of asymmetric divisions responsible for patterning. These data will also provide a framework for the analysis of Arabidopsis mutants that affect stomatal patterning and morphogenesis.