THE REVOLUTA GENE IS NECESSARY FOR APICAL MERISTEM DEVELOPMENT AND FOR LIMITING CELL DIVISIONS IN THE LEAVES AND STEMS OF ARABIDOPSIS-THALIANA

The form of seed plants is determined by the growth of a number of mer istems including apical meristems, leaf meristems and cambium layers, We investigated five recessive mutant alleles of a gene REVOLUTA that is required to promote the growth of apical meristems and to limit cel l division in leaves and stems of Arabidopsis thaliana. REVOLUTA maps to the bottom of the fifth chromosome, Apical meristems of both paracl ades (axillary shoots) and flowers of revoluta mutants frequently fail tocomplete normal development and form incomplete or abortive structur es. The primary shoot apical meristem sometimes also arrests developme nt early, Leaves, stems and floral organs, in contrast, grow abnormall y large, We show that in the leaf epidermis this extra growth is due t o extra cell divisions in the leaf basal meristem, The extent of leaf growth is negatively correlated with the development of a paraclade in the leaf axil. The thickened stems contain extra cell layers, arrange d in rings, indicating that they may result from a cambium-like merist em, These results suggest that the REVOLUTA gene has a role in regulat ing the relative growth of apical and non-apical meristems in Arabidop sis.