Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2005
Publication Date: 2/1/2006
Citation: Krizek, B.A., Lewis, M.W., Fletcher, J.C. 2006. RABBIT EARS is a second-whorl repressor of AGAMOUS that maintains spatial boundaries in Arabidopsis flowers. Plant Journal. 45(3):369-83. Interpretive Summary: This paper describes a new role for the RABBIT EARS (RBE) zinc finger protein in maintaining the boundaries between different organs in Arabidopsis flowers. We identified a novel allele of RBE that has disrupted sepal separation and defective petal development. The rbe mutant petals were often replaced by stamen-like organs, and incorrectly expressed the stamen identity gene AGAMOUS (AG). Our genetic studies determined that a functional AG gene is required for both these phenotypes. Double mutant analysis revealed that RBE acts after the UFO gene in controlling petal development. Our work demonstrates that RBE is a specific repressor of AG that maintains the separation between developing organs within a specific domain as well as boundaries of gene expression between different domains.
Technical Abstract: The RABBIT EARS (RBE) gene has been identified as a regulator of petal development in Arabidopsis thaliana. We find that second-whorl petals in rbe mutants can be replaced with staminoid organs, stamens or filaments and that some rbe flowers have increased numbers of sepals and exhibit fusion of sepals. We show that these rbe defects are due to AGAMOUS (AG) misexpression in the second whorl. Consistent with its role in maintaining the spatial boundary of AG expression, rbe enhanced the second-whorl defects present in ap2-1, lug-1 and clf-2 mutants. In the development of second-whorl organs, RBE acts in the same pathway and downstream of UNUSUAL FLORAL ORGANS (UFO). Enhanced first-whorl organ fusion in ap2-2 rbe-3, ant-4 rbe-3 and cuc2-1 rbe-3 double mutants supports an additional role for RBE in organ separation. RBE thus acts to maintain two different types of spatial boundaries in young flowers: boundaries between organ primordia within a whorl and boundaries of homeotic gene expression between whorls.