Control of flower development in <i>Arabidopsis thaliana</i> by <i>APETALA1</i> and interacting genes

TLDR

Mutations in APETALA1 disrupt flower meristem specification and floral organ specification. The study examines an allelic series of nine apetala1 mutants to demonstrate that APETALA1’s two functions are separable. The authors used an allelic series of nine apetala1 mutants, phenotypic analysis of multiple mutants, and in situ hybridization of floral control genes to dissect APETALA1 functions. APETALA1 and LEAFY together ensure floral fate of inflorescence apex primordia, with overlapping, reinforcing functions; CAULIFLOWER positively regulates both genes and is redundant with APETALA1; APETALA2 also reinforces their activity, particularly when either is mutated, and APETALA1 interacts with APETALA2 to control outer whorl development.

Abstract

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. CAU - LIFLOWER 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.