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Microtubule Arrays and Cell Divisions of Stomatal Development in Arabidopsis

出版	Ohio State University, 2007
URL	http://books.google.com.hk/books?id=UsCyuAAACAAJ&hl=&source=gbs_api

註釋Abstract: Little is known about how preprophase bands (PPBs) of microtubules mark division sites, or how phragmoplasts later grow towards these sites. To more clearly define these aspects of cell division, PPBs and phragmoplasts were characterized in three dimensions in living Arabidopsis leaf epidermal cells that expressed a constitutively active alpha-tubulin-GFP construct. Contrary to classical models of cell division, both PPBs and phragmoplasts were found to form asymmetrically in that the arrays appear first in the cell cortex adjacent to the mesophyll. Cell division was also examined in tonneau2 (ton2). Despite the absence of PPBs in ton2, preprophase nuclei are properly positioned in the inner cell cortex. However, cytokinesis is incomplete and phragmoplasts are visibly disrupted, showing that TON2 is also needed for cytokinesis, not just for PPB formation. In wild-type plants, PPBs and phragmoplasts are oriented away from three different types of stomatal precursor cells, supporting the idea that intercellular signaling patterns stomata. The interphase microtubule arrays of guard mother cells and guard cells were characterized by stage. Abnormal stomatal clusters form in the too many mouths (tmm) mutant due to misplaced asymmetric divisions. PPBs and phragmoplasts in tmm are also misplaced, but otherwise normal in development and structure. This suggests that TMM helps laterally orient asymmetric divisions, but that it is not required for the asymmetric inner-to-outer development of the PPB or phragmoplast. Finally, the predictable polarity of cytokinesis was used to help define the stages of cortical microtubule re-population at the cytokinesis-interphase transition in wild-type plants. Although previous reports using cultured cells suggested that the first interphase microtubules form at the nuclear surface, I found that microtubules initiate directly in the cell cortex. These results suggest that the interphase array can arise from direct seeding of microtubules in the cell cortex. Overall this work provides an analysis of the spatial and temporal features of microtubule array development in the Arabidopsis leaf epidermis, with special attention to critical cell types and cell division. This analysis provides a framework for analyzing the cell biological features of genes that affect division, the cytoskeleton, cell wall formation, differentiation, and morphogenesis.