Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2003
Publication Date: 2/12/2004
Citation: Hoecker, U., Toledo-Ortiz, G., Bender, J., Quail, P.H. 2004. The photomorphogenesis-related mutant red1 is defective in CYP83b1, a red light-induced gene encoding a cytochrome P450 required for normal auxin homeostasis. Planta. 219:195-200. Interpretive Summary: Previous genetic analysis identified a component, RED1, that is required for normal development of Arabidopsis seedlings in response to red light (Rc). We have now shown that red1 mutants are defective in the cytochrome P450 CYP83B1, an enzyme required for normal auxin homeostasis. The evidence indicates that red-light induction of the CYP83B1 gene may be necessary for normal seedling development via the auxin hormone system.
Technical Abstract: Previous genetic analysis identified a component, RED1, that is required for normal de-etiolation of Arabidopsis thaliana (L.) Heynh. seedlings in continuous red light (Rc). red1 mutant seedlings exhibit elongated hypocotyls and reduced cotyledon size specifically in Rc and not in continuous far-red light (FRc). Here, we show that red1 is allelic to sur2 and atr4, and is defective in the cytochrome P450 CYP83B1, an enzyme required for normal auxin homeostasis. Two alleles of atr4, like red1, exhibit increased hypocotyl elongation and reduced cotyledon expansion in Rc but not in FRc. We further show that CYP83B1 transcript levels are elevated specifically in Rc-grown seedlings when compared with seedlings grown in darkness or FRc. Hence, the Rc-specific phenotype of the red1 mutant may indicate that Rc-induction of the CYP83B1 transcript is necessary for normal seedling de-etiolation in the wild type.