A mutation in the Arabidopsis DET3 gene uncouples photoregulated leaf development from gene expression and chloroplast biogenesis

Abstract

The genetic and phenotypic characterization of a new Arabidopsis mutant, de-etiolated-3, (det3), involved in light-regulated seedling development is described. A recessive mutation in the DET3 gene uncouples light signals from a subset of light-dependent processes. The det3 mutation causes dark-grown Arabidopsis thaliana seedlings to have short hypocotyls, expanded cotyledons, and differentiated leaves, traits characteristic of light-grown seedlings. Despite these morphological changes, however, the det3 mutant does not develop chloroplasts or show elevated expression of nuclear- and chloroplast-encoded light-regulated mRNAs. The det3 mutation thus uncovers a downstream branch of the light transduction pathways that separates leaf development from chloroplast differentiation and light-regulated gene expression. In addition, light-grown det3 plants have reduced stature and apical dominance, suggesting that DET3 functions during growth in normal light conditions as well. The genetic interactions between mutations in det1, det2, and det3 are described. The phenotypes of doubly mutant strains suggest that there are at least two parallel pathways controlling light-mediated development in Arabidopsis.