GENETIC-ANALYSIS OF ORGAN FUSION IN ARABIDOPSIS-THALIANA

Postgenital organ fusion occurs most commonly during reproductive deve lopment and is important in many angiosperms during genesis of the car pel. Although a number of mutants have been described that manifest ec topic organ fusion, little is known about the genes involved in regula ting this process. In this article we describe the characterization of a collection of 29 Arabidopsis mutants showing an organ fusion phenot ype. Mapping and complementation analyses revealed that the mutant all eles define nine different loci distributed throughout the Arabidopsis genome. Multiple alleles were isolated for the four complementation g roups showing the strongest organ fusion phenotype while the remaining five complementation groups, all of which show only weak floral organ fusion, have a single representative allele. In addition to fusion ev ents between aerial parts of the shoot, some mutants also show abnorma l ovule morphology with adjacent ovules joined together at maturity. M any of the fusion mutants isolated have detectable differences in the rate at which chlorophyll can be extracted; however, in one case no di fference could be detected between mutant and wild-type plants. In thr ee mutant lines pollen remained unresponsive to contact with the mutan t epidermis, demonstrating that organ fusion and pollen growth respons es can be genetically separated from one another.