Regulation of meristem organization and cell division by TSO1, an Arabidopsis gene with cysteine-rich repeats

In higher plants, meristem organization and cell division regulation are tw o fundamentally important and intimately related biological processes. Iden tifying and isolating regulatory genes in these processes is essential for understanding higher plant growth and development. We describe the molecula r isolation and analyses of an Arabidopsis gene, TSO1, which regulates both of these processes. We previously showed that tso1 mutants displayed defec ts in cell division of floral meristem cells including partially formed cel l walls, increased DNA content, and multinucleated cells (Liu, Z., Running, M. P, and Meyerowitz, E, M, (1997), Development 124, 665-672), Here, we ch aracterize a second defect of tso1 in inflorescence meristem development an d show that the enlarged inflorescence in tso1 mutants results from repeate d division of one inflorescence meristem into two or more inflorescence mer istems, Using a map-based approach, we isolated the TSO1 gene and found tha t TSO1 encodes a protein with cysteine-rich repeats bearing similarity to D rosophila Enhancer of zeste and its plant homologs, In situ TSO1 mRNA expre ssion pattern and the nuclear localization of TSO1-GFP are consistent with a regulatory role of TSO1 in floral meristem cell division and in infloresc ence meristem organization.