RT Journal Article SR Electronic T1 A Complement of Ten Essential and Pleiotropic Arabidopsis COP/DET/FUS Genes Is Necessary for Repression of Photomorphogenesis in Darkness JF Plant Physiology JO Plant Physiol. FD American Society of Plant Biologists SP 731 OP 742 DO 10.1104/pp.110.3.731 VO 110 IS 3 A1 Kwok, S. F. A1 Piekos, B. A1 Misera, S. A1 Deng, X. W. YR 1996 UL http://www.plantphysiol.org/content/110/3/731.abstract AB Two genetic screens, one for mutations resulting in photomorphogenic development in darkness and the other for mutants with fusca phenotype, have thus far identified six pleiotropic Arabidopsis COP/DET/FUS genes. Here, we characterized representative mutants that define four additional pleiotropic photomorphogenic loci and a null mutant allele of the previously defined DET1 locus. Dark-grown seedlings homozygous for these recessive mutations exhibit short hypocotyls and expanded cotyledons and are lethal before reaching reproductive development. Dark-grown mutant seedlings also display characteristic photomorphogenic cellular differentiation and elevated expression of light-inducible genes. In addition, analyses of plastids from dark-grown mutants reveal partial chloroplast differentiation and absence of etioplast development. Root vascular bundle cells of light-grown mutant seedlings develop chloroplasts, suggesting that these FUS gene products are important for suppression of chloroplast differentiation in light-grown roots. Double-mutant analyses indicate that these pleiotropic cop/det/fus mutations are epistatic to mutations in phytochromes, a blue-light photoreceptor, and a downstream regulatory component, HY5. Therefore, there is a complement of at least 10 essential and pleiotropic Arabidopsis genes that are necessary for repression of photomorphogenic development.