| Summary: | <p>Abstract</p> <p>Background</p> <p>The Arabidopsis <it>SEUSS </it>(<it>SEU</it>) gene encodes a transcriptional adaptor protein that is required for a diverse set of developmental events, including floral organ identity specification, as well as gynoecium, ovule and embryo development. In order to better understand the molecular mechanisms of <it>SEUSS </it>action we undertook a genetic modifier screen to identify <it>seuss-modifier </it>(<it>sum</it>) mutations.</p> <p>Results</p> <p>Screening of M2 lines representing approximately 5,000 M1 individuals identified mutations that enhance the <it>seuss </it>mutant phenotypic disruptions in ovules and gynoecia; here we describe the phenotype of the <it>sum63 </it>mutant and enhanced disruptions of ovule and gynoecial development in the <it>seu sum63 </it>double mutant. Mapping and genetic complementation tests indicate that <it>sum63 </it>is allelic to <it>CYP85A2 </it>(AT3G30180) a cytochrome p450 enzyme that catalyzes the final steps in the synthesis of the phytohormone brassinolide.</p> <p>Conclusions</p> <p>Our identification of mutations in <it>CYP85A2 </it>as enhancers of the <it>seuss </it>mutant phenotype suggests a previously unrecognized role for brassinolide synthesis in gynoecial and ovule outer integument development. The work also suggests that <it>seuss </it>mutants may be more sensitive to the loss or reduction of brassinolide synthesis than are wild type plants.</p>
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