Differential degradation of PIN2 auxin efflux carrier by retromer-dependent vacuolar targeting

Abstract

All eukaryotic cells present at the cell surface a specific set of plasma membrane proteins that modulate responses to internal and external cues and whose activity is also regulated by protein degradation. We characterized the lytic vacuole-dependent degradation of membrane proteins in Arabidopsis thaliana by means of in vivo visualization of vacuolar targeting combined with quantitative protein analysis. We show that the vacuolar targeting pathway is used by multiple cargos including PIN-FORMED (PIN) efflux carriers for the phytohormone auxin. In vivo visualization of PIN2 vacuolar targeting revealed its differential degradation in response to environmental signals, such as gravity. In contrast to polar PIN delivery to the basal plasma membrane, which depends on the vesicle trafficking regulator ARF-GEF GNOM, PIN sorting to the lytic vacuolar pathway requires additional brefeldin Asensitive ARF-GEF activity. Furthermore, we identified putative retromer components SORTING NEXIN1 (SNX1) and VACUOLAR PROTEIN SORTING29 (VPS29) as important factors in this pathway and propose that the retromer complex acts to retrieve PIN proteins from a late/pre-vacuolar compartment back to the recycling pathways. Our data suggest that ARF GEF-and retromer-dependent processes regulate PIN sorting to the vacuole in an antagonistic manner and illustrate instrumentalization of this mechanism for fine-tuning the auxin fluxes during gravitropic response.gravitropism ͉ polar auxin transport ͉ posttranslational regulation ͉ vesicle trafficking

COP1 mediates the coordination of root and shoot growth by light through modulation of PIN1- and PIN2-dependent auxin transport in Arabidopsis

“…As demonstrated previously, darkness induces drastic changes in PIN1 and PIN2 intracellular localization in agar-grown roots (Laxmi et al, 2008;Kleine-Vehn et al, 2008) (Fig. 5E,F).…”

“…The changes in PIN2 intracellular distribution in darkness have been proposed to result from a higher ubiquitination rate of PIN2, leading to degradation in vacuoles (Kleine-Vehn et al, 2008;Leitner et al, 2012). As previously reported using MG132 (Abas et al, 2006;Laxmi et al, 2008), specific inhibition of proteasome activity using lactacystin blocked PIN2-GFP targeting to the vacuole in darkness (supplementary material Fig.…”

“…Development 139 (18) at the PM and accumulating in the lytic vacuole (Kleine-Vehn et al, 2008;Laxmi et al, 2008) (our data). Furthermore, we have demonstrated that inhibition of shoot-to-root PAT using NPA application on hypocotyls of light-grown seedlings decreases PIN2 levels at the PM in the RAM, and causes root phenotypes similar to those of etiolated seedlings.…”

“…Moreover, recent data show that darkness rapidly triggers a change in the intracellular distribution of several PIN 3403 RESEARCH ARTICLE COP1 regulates root growth proteins in the root apical meristem (RAM), which was proposed to lead to a local alteration of auxin transport and to a decrease in root growth (Laxmi et al, 2008). In the case of PIN2, strong evidence indicates that this occurs through a decrease in PIN2 protein levels at the PM that is triggered by degradation through vacuolar targeting of the protein, similarly to gravitropic responses (Kleine-Vehn et al, 2008;Leitner et al, 2012).…”

ESCRT-I Component VPS23A Affects ABA Signaling by Recognizing ABA Receptors for Endosomal Degradation

“…Known targets of the endocytic trafficking route in plants include the auxin carriers PIN1, PIN2, and AUX1, the iron transporter IRT1, the boric acid/borate exporter BOR1, the flagellin receptor FLS2, the brassinosteroid receptor BRI1, and the high-affinity phosphate transporter PHT1 (Barberon et al, 2011;Bayle et al, 2011;Geldner et al, 2001;Kasai et al, 2011;Kleine-Vehn et al, 2006;Kleine-Vehn et al, 2008;Spallek et al, 2013;Spitzer, et al, 2009). (Slagsvold et al, 2006).…”