HAWAIIAN SKIRT: An F-Box Gene That Regulates Organ Fusion and Growth in Arabidopsis

Zinnia H GonzáLez-Carranza,Unchalee Rompa,Anthony D Stead,Jeremy A Roberts,Janny L Peters,Janny L Peters,Jeremy A Roberts,Anthony D Stead,Anthony D Stead,Janny L Peters,Carol Wagstaff,Jeremy A Roberts,Anuj M Bhatt,Carol Wagstaff,Anuj M Bhatt,Unchalee Rompa,Carol Wagstaff,Janny L Peters,Carol Wagstaff,Carol Wagstaff,Jeremy A Roberts,Anuj M Bhatt,Anthony D Stead,Unchalee Rompa,Unchalee Rompa,Anuj M Bhatt,Anthony D Stead,Janny L Peters,Anuj M Bhatt,Jeremy A Roberts,Unchalee Rompa

doi:10.1104/pp.106.092288

Abstract

A fast neutron-mutagenized population of Arabidopsis (Arabidopsis thaliana) Columbia-0 wild-type plants was screened for floral phenotypes and a novel mutant, termed hawaiian skirt (hws), was identified that failed to shed its reproductive organs. The mutation is the consequence of a 28 bp deletion that introduces a premature amber termination codon into the open reading frame of a putative F-box protein (At3g61590). The most striking anatomical characteristic of hws plants is seen in flowers where individual sepals are fused along the lower part of their margins. Crossing of the abscission marker, Pro(PGAZAT):beta-glucuronidase, into the mutant reveals that while floral organs are retained it is not the consequence of a failure of abscission zone cells to differentiate. Anatomical analysis indicates that the fusion of sepal margins precludes shedding even though abscission, albeit delayed, does occur. Spatial and temporal characterization, using Pro(HWS):beta-glucuronidase or Pro(HWS):green fluorescent protein fusions, has identified HWS expression to be restricted to the stele and lateral root cap, cotyledonary margins, tip of the stigma, pollen, abscission zones, and developing seeds. Comparative phenotypic analyses performed on the hws mutant, Columbia-0 wild type, and Pro(35S):HWS ectopically expressing lines has revealed that loss of HWS results in greater growth of both aerial and below-ground organs while overexpressing the gene brings about a converse effect. These observations are consistent with HWS playing an important role in regulating plant growth and development.

Highlights

A fast neutron-mutagenized population of Arabidopsis (Arabidopsis thaliana) Columbia-0 wild-type plants was screened for floral phenotypes and a novel mutant, termed hawaiian skirt, was identified that failed to shed its reproductive organs
Other mutants from Arabidopsis that show varying degrees of sepal fusion include unusual floral organs where the mutated gene has been shown to encode an F-box protein (Levin and Meyerowitz, 1995; Samach et al, 1999); leafy, which is the result of a mutation in a floral meristem identity gene (Schultz and Haughn, 1991; Weigel and Meyerowitz, 1993); and the cup shaped cotyledon mutants that arise as a consequence of mutations in putative NAC-transcription factor genes (Aida et al, 1997; Takada et al, 2001; Vroemen et al, 2003)
A number of other genes have been shown to play an important role in the specification of lateral organ boundaries in leaves or flowers including LATERAL ORGAN BOUNDARIES (Shuai et al, 2002), LATERAL ORGAN JUNCTIONS (Prasad et al, 2005), PETAL LOSS (Brewer et al, 2004), the FUSED FLORAL ORGANS (FFO) loci (FFO1, FFO2, FFO3; Levin et al, 1998), HANABA TARANU (Zhao et al, 2004), and RABBIT EARS (Krizek et al, 2006)