Showing papers by "Detlef Weigel published in 1993"

Control of flower development in Arabidopsis thaliana by APETALA1 and interacting genes

Abstract: Mutations in the APETALA1 gene disturb two phases of flower development, flower meristem specification and floral organ specification. These effects become manifest as a partial conversion of flowers into inflorescence shoots and a disruption of sepal and petal development. We describe the changes in an allelic series of nine apetala1 mutants and show that the two functions of APETALA1 are separable. We have also studied the interaction between APETALA1 and other floral genes by examining the phenotypes of multiply mutant plants and by in situ hybridization using probes for several floral control genes. The results suggest that the products of APETALA1 and another gene, LEAFY, are required to ensure that primordia arising on the flanks of the inflorescence apex adopt a floral fate, as opposed to becoming an inflorescence shoot. APETALA1 and LEAFY have distinct as well as overlapping functions and they appear to reinforce each other's action. CAULIFLOWER is a newly discovered gene which positively regulates both APETALA1 and LEAFY expression. All functions of CAULIFLOWER are redundant with those of APETALA1. APETALA2 also has an early function in reinforcing the action of APETALA1 and LEAFY, especially if the activity of either is compromised by mutation. After the identity of a flower primordium is specified, APETALA1 interacts with APETALA2 in controlling the development of the outer two whorls of floral organs.

Activation of floral homeotic genes in Arabidopsis.

Abstract: The identity of floral organs in Arabidopsis thaliana is determined by homeotic genes, which are expressed in specific regions of the developing flower. The initial activation of homeotic genes is accomplished at least in part by the products of two earlier acting genes with overlapping functions. These are the floral meristem—identity genes LEAFY and APETALA1. The requirements of LEAFY and APETALA1 activity vary for different homeotic genes.

Leafy Controls Meristem Identity in Arabidopsis

Abstract: Flower development can be broken down into at least five steps: (1) Upon floral induction, the vegetative shoot meristem is converted into an inflorescence meristem. (2) The inflorescence meristem starts to generate floral meristems, or is itself transformed into a floral meristem. This step can be preceded by the generation of a limited number of secondary inflorescence meristems by the primary inflorescence meristem. (3) The floral meristems produce floral organ primordia. (4) The floral organ primordia adopt different fates according to their position within the developing flower. (5) The floral organ primordia differentiate into floral organs. Despite many efforts, very little is known about the molecules directing these processes. Since classical physiological approaches toward understanding flower development have met only with limited success, a genetic-molecular approach has recently been chosen by several groups (e.g., Komaki et al., 1988; Bowman et al., 1989, 1991, 1992; Hill and Lord, 1989; Kunst et al., 1989; Sommer et al., 1990; Yanofsky et al., 1990; Irish and Sussex, 1990; Carpenter and Coen, 1990; Coen et al., 1990; Martinez-Zapater and Somerville, 1990; Drews et al., 1991; Goto et al., 1991; Koornneef et al., 1991; Schultz and Haughn, 1991; Schultz et al. 1991; Shannon and Meeks-Wagner, 1991; Alvarez et al., 1992; Schwarz-Sommer et al., 1992; Jack et al., 1992; Huijser et al., 1992; Weigel et al., 1992; Huala and Sussex, 1992). The underlying rationale is to first identify mutations that specifically affect different steps of flower development, then to analyze these mutations at the genetic level, and finally to clone the corresponding genes to determine their function at the molecular level.