Membrane Association of theArabidopsisARF Exchange Factor GNOM Involves Interaction of Conserved Domains

Abstract

The GNOM protein plays a fundamental role in Arabidopsis thaliana development by regulating endosome-to-plasma membrane trafficking required for polar localization of the auxin efflux carrier PIN1. GNOM is a family member of large ARF guanine nucleotide exchange factors (ARF-GEFs), which regulate vesicle formation by activating ARF GTPases on specific membranes in animals, plants, and fungi. However, apart from the catalytic exchange activity of the SEC7 domain, the functional significance of other conserved domains is virtually unknown. Here, we show that a distinct N-terminal domain of GNOM mediates dimerization and in addition interacts heterotypically with two other conserved domains in vivo. In contrast with N-terminal dimerization, the heterotypic interaction is essential for GNOM function, as mutations abolishing this interaction inactivate the GNOM protein and compromise its membrane association. Our results suggest a general model of large ARF-GEF function in which regulated changes in protein conformation control membrane association of the exchange factor and, thus, activation of ARFs.

Hormonal Regulation of Lateral Root Development in Arabidopsis Modulated byMIZ1and Requirement of GNOM Activity forMIZ1Function

“…GNOM interacts with other GNOM proteins via the SEC7-DCB domain, forming GNOM dimers (Anders et al, 2008). Since disruption of dimerization activity abolishes the membrane association of GNOM, severe developmental defects are observed in gnom mutants lacking heterotypic interactions (Anders et al, 2008). In contrast, the miz2 mutants were not defective in organ development, and the site of the miz2 mutation was not located in the GNOM dimerization region (Miyazawa et al, 2009b).…”

“…Moreover, overexpression of MIZ1 did not affect GNOM localization or endosomal vesicle trafficking activity. GNOM interacts with other GNOM proteins via the SEC7-DCB domain, forming GNOM dimers (Anders et al, 2008). Since disruption of dimerization activity abolishes the membrane association of GNOM, severe developmental defects are observed in gnom mutants lacking heterotypic interactions (Anders et al, 2008).…”

The role of decapping proteins in the miRNA accumulation inArabidopsis thaliana

“…[42][43][44] These proteins are not involved in any miRNA pathway. We used dcp1-1 as a decapping mutant in Col-0 background with such mutants in the experiment (Fig.…”

Adventitious root formation in rice requires OsGNOM1 and is mediated by the OsPINs family

“…Most of these mutants exhibited severe defects in both early embryonic structure and subsequent post-embryonic development such as LR formation and gravitropism, resulting in lethality [19,22,23]. GNOM is found in ORIGINAL ARTICLE www.cell-research.com | Cell Research Shiping Liu et al 1111 npg endosomal compartments and catalyzes guanine nucleotide exchange through its SEC7 domain, which is highly conserved among animals, plants and fungi [21,[24][25][26]. Except for GL1 in Arabidopsis, most large ARF-GEFs in plants (including GNOM) are predicted to be sensitive to the fungal toxin brefeldin A (BFA), a specific inhibitor of membrane protein trafficking [27,28].…”