Abstract
Light is one of the most important environment factors. Plants orientate their growth with respect to the direction of light(phototropism) or gravity(gravitropism). It has widely recognized that phototropism of Arabidopsis seedlings is subject to blue-light. We isolated an Arabidopsis mutant, which represents curved hypocotyls under red-light condition. In this mutant, designated as flabby, the curving directions are not depend on the direction of red-light illumination while they showed normal phototropism by blue-light, and gravitropism, suggesting that there is red-light dependent deviation control. Fine mapping was used to identify flabby gene, and revealed that FLABBY encodes one of the gene family of ABC transporter, AtMDR1. AtMDR1, a homolog of multi-drug resistance gene of animals regulates auxin transport in Arabidopsis as previously reported. NPA, auxin transport inhibitor suppressed the phenotype, suggesting that there is red-light dependent auxin efflux control through AtMDR1.
