A FUSCA gene of Arabidopsis encodes a novel protein essential for plant development.

Abstract

Arabidopsis fusca mutants display striking purple coloration due to anthocyanin accumulation in their cotyledons. We describe six recessive fusca mutants isolated from Agrobacterium-transformed Arabidopsis families. These mutants first become defective during embryogenesis and exhibit limited seedling development. Double mutant constructs revealed that developmental defects were not simply a consequence of anthocyanin accumulation. fusca seedlings showed al- tered responses to severa1 environmental and endogenous factors. Allelism tests established that three fusca loci are represented by mutants previously described as defective in light-regulated responses. To study the molecular basis of the fusca phenotype, we cloned the FUSG gene. FUS6 encodes a nove1 protein that is hydrophilic, a-helical, and con- tains potential protein kinase C phosphorylation sites. The FUSCA proteins appear to act in a network of signal transduction pathways critical for plant development.