DORNROSCHEN-LIKE, an AP2 gene, is necessary for stamen emergence in Arabidopsis

To identify novel genes in petal and stamen development, a genetic screen was carried out for enhancers of the unusual B class mutant pistillata-5 (pi-5). In pi-5 flowers, second whorl organs develop as sepals rather than petals, but third whorl stamens are normal. One pi-5 enhancer, dornroschen-like-2 (drnl-2), results in third whorl positions developing as filamentous organs. In addition to enhancing the pi-5 phenotype, drnl-2 mutants also exhibit a phenotype in a wild-type PI background. Although stamen primordia are morphologically visible during early stages of flower development, they fail to enlarge in drnl-2 mutants. DRNL, which encodes a single AP2 domain protein, is expressed in a dynamic pattern in the embryo, seedling, and flower. Analysis of both the drnl-2 mutant phenotype and the DRNL expression pattern in flowers suggests that DRNL plays a critical role in stamen emergence in Arabidopsis.