Submitted to: Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2001
Publication Date: 4/1/2001
Interpretive Summary: This article reports the identification and characterization of a novel Arabidopsis mutant called ULTRAPETALA (ULT). ult mutant plants form more flowers than wild type plants, and the mutant flowers contain more organs than normal. I performed a series of morphological and genetic studies of ult mutant plants, the results of which indicated that the wild type function of the ULT gene is to prevent the formation of extra cells in developing shoots and flowers. These results demonstrate that the ULT gene has important functions in Arabidopsis development
Technical Abstract: The regulation of proper shoot and floral meristem size during plant development is mediated by a complex interaction of stem cell promoting and restricting factors. Here I describe the phenotypic effects of mutations in the ULTRAPETALA (ULT) gene, which is required to control shoot and floral meristem cell accumulation in Arabidopsis thaliana. ultrapetala flowers contain more floral organs and whorls than wild type plants, phenotypes which correlate with an increase in floral meristem size preceding organ initiation. ultrapetala plants also produce more floral meristems than wild type plants, correlating with an increase in inflorescence meristem size without visible fasciation. Expression analysis indicates that ULTRAPETALA controls meristem cell accumulation in part by limiting the domain of CLAVATA1 expression. Genetic studies show that ULTRAPETALA acts independently of ERA1, but has overlapping functions with PERIANTHIA and the CLAVATA signal transduction pathway in controlling shoot and floral meristem size and meristem determinacy. Thus ULTRAPETALA defines a novel locus that restricts meristem cell accumulation in Arabidopsis shoot and floral meristems.