title: Membrane-associated binding sites for indoleacetic acid in the rice coleoptile.
abstract: As described previously, the sensitivity of rice (Oryza sativa L.) coleoptiles to auxin is modulated by oxygen. Under anoxia, coleoptile elongation is insensitive to exogenously applied indole-3-acetic acid (IAA), whereas its sensitivity increases in air in the presence of the exogenous stimulus. Here we report the presence of two independent classes of membrane-bound IAA-binding sites in air-grown coleoptiles. Their binding activity is strictly correlated with the system's sensitivity to IAA. We designate them as site A (high affinity) and site B (low affinity). Site A shows a relatively fast response to anoxia, and is highly specific for auxins. Regulation of site-A binding activity through ATP, whose availability decreases under anoxia, is postulated. A role as auxin carrier is suggested for site B.
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto Biosintesi Vegetali, Via Bassini 15, I-20133, Milano, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Zaina
authors.forename: A
authors.initials: A
authors.lastname: Bertani
authors.forename: L
authors.initials: L
authors.lastname: Lombardi
authors.forename: S
authors.initials: S
authors.lastname: Mapelli
authors.forename: G
authors.initials: G
authors.lastname: Torti