In vitro and in vivo evidence for actin association of the naphthylphthalamic acid‐binding protein from zucchini hypocotyls

Abstract

SummaryThe N-1-naphthylphthalamic acid (NPA)-binding protein is part of the auxin efflux carrier, the protein complex that controls polar auxin transport in plant tissues. This study tested the hypothesis that the NPA-binding protein (NBP) is associated with the actin cytoskeleton in vitro and that an intact actin cytoskeleton is required for polar auxin transport in vivo. Cytoskeletal

Interactions between Auxin Transport and the Actin Cytoskeleton in Developmental Polarity ofFucus distichusEmbryos in Response to Light and Gravity

“…The possibility that auxin efflux proteins are among these targeted proteins merits consideration. Increasing LatB concentrations increased IAA accumulation in F. distichus embryos, consistent with an inhibition of IAA efflux when actin is fragmented, and similar to reports that IAA transport is reduced by drugs that fragment the actin cytoskeleton (Butler et al, 1998). This effect might be mediated by altering the cycling of IAA efflux carriers to the plasma membrane, as suggested in Arabidopsis (Geldner et al, 2001).…”

“…This IAA efflux complex likely consists of several proteins, including an integral membrane protein, which may be encoded by a PIN gene (Palme and Gälweiler, 1999) and/or an MDR-like gene (Noh et al, 2001), and a peripheral membrane regulatory protein, or NPAbinding protein (Muday, 2000). An NPA-binding protein has been reported to interact with the actin cytoskeleton (Butler et al, 1998;Hu et al, 2000), and this interaction may facilitate the asymmetric localization of the efflux carrier. The role of the actin interaction of this protein complex may be in modulation of the cycling of IAA efflux transporters from internal compartments to the membrane surface (Geldner et al, 2001(Geldner et al, , 2003.…”

Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins

“…NPA indeed interferes with PIN1 trafficking after disruption by the lactone antibiotic, brefeldin A [105], as well as in the tir3 mutant lacking the scaffolding protein, BIG [119]. It was also shown in an earlier study that the number of NPA-binding sites and polar auxin transport are reduced in the tir3/big mutant [109], collectively supporting a connection between NPA binding to the cytoskeleton, PIN trafficking, and auxin transport. On the other hand, evidence suggests that the interference of auxin-transport inhibitors with the actin status might be indirect.…”

“…These two modes of actions for NPA on auxin transport, which could be even interconnected [7], might be represented by two distinct NPA binding affinities, as reported for zucchini plasma membrane and speculated to correspond to the auxin transporter itself and an additional NPA-binding regulatory subunit [106]. While the number of NPA binding sites in the plant cell is currently highly debated [107], there is general agreement that NPA binding is peripheral to the plasma membrane and associated with the actin cytoskeleton [108][109][110].…”

Mutation of the Membrane-Associated M1 Protease APM1 Results in Distinct Embryonic and Seedling Developmental Defects inArabidopsis

“…In contrast with the ABCB integral membrane proteins isolated by NPA affinity chromatography whose activity is inhibited by NPA Taiz, 1999a, 1999b;Murphy et al, 2000Murphy et al, , 2002Noh et al, 2001Noh et al, , 2003Geisler et al, 2003Geisler et al, , 2005Terasaka et al, 2005), an NPA binding peripheral membrane protein from cucurbits appeared to be associated with the actin cytoskeleton (Cox and Muday, 1994;Butler et al, 1998). As APM1 is a peripheral membrane protein that binds both free and conjugated NPA (Murphy et al, 2000(Murphy et al, , 2002Smith et al, 2003), we examined the cytoskeletal dependence of APM1 localization.…”