Abstract
The Arabidopsis (Arabidopsis thaliana) gynoecium, the female floral reproductive structure, requires the action of genes that specify positional identities during its development to generate an organ competent for seed development and dispersal. Early in gynoecial development, patterning events divide the primordium into distinct domains that will give rise to specific tissues and organs. The medial domain of the gynoecium gives rise to the ovules, and several other structures critical for reproductive competence. Here we report a synergistic genetic interaction between seuss and aintegumenta mutants resulting in a complete loss of ovule initiation and a reduction of the structures derived from the medial domain. We show that patterning events are disrupted early in the development of the seuss aintegumenta gynoecia and we identify PHABULOSA (PHB), REVOLUTA, and CRABS CLAW (CRC) as potential downstream targets of SEUSS (SEU) and AINTEGUMENTA (ANT) regulation. Our genetic data suggest that SEU additionally functions in pathways that are partially redundant and parallel to PHB, CRC, and ANT. Thus, SEU and ANT are part of a complex and robust molecular system that coordinates patterning cues and cellular proliferation along the three positional axes of the developing gynoecium.
Highlights
The Arabidopsis (Arabidopsis thaliana) gynoecium, the female floral reproductive structure, requires the action of genes that specify positional identities during its development to generate an organ competent for seed development and dispersal
To determine if abaxial fate was expanded in seu ant mutant carpels, we examined the expression of the gynoecial abaxial fate determinants YAB1/FIL and CRABS CLAW (CRC) by in situ hybridization
Our results indicate that SEU and ANT share a number of partially redundant functions during Arabidopsis development
Summary
The seu single mutant has reduced stem length and shorter, rounder leaves (Franks et al, 2002). Again we detected a reduction of expression within the adaxial core of the gynoecium at stages 5 and 6 that was more obvious in the seu ant double mutant than in the ant single mutant (compare Fig. 3L with Fig. 3D) This phenotype was not fully penetrant at this stage, but was observed in more than half of the gynoecia examined. In the seu ant double mutant, REV expression is strongly detected in the adaxial core of gynoecia (stages 6 and 7) at levels similar to wild type (Fig. 3, Q and R). Plants expressing the 35S:PHB construct are wild type in appearance, are self-fertile, and display normal ovule initiation and development (McConnell et al, 2001; Prigge et al, 2005) likely due to the targeted degradation of PHB transcripts by microRNAs 165/166 in abaxial domains (Emery et al, 2003). The phb-1d/1 seu ant mutant gynoecia were very similar phenotypically to those of the seu ant double mutants in that medial domains formed but failed to generate ovule primordia (Fig. 7L)
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