Abstract
The heterotrimeric G-protein complex provides signal amplification and target specificity. The Arabidopsis (Arabidopsis thaliana) Gβ-subunit of this complex (AGB1) interacts with and modulates the activity of target cytoplasmic proteins. This specificity resides in the structure of the interface between AGB1 and its targets. Important surface residues of AGB1, which were deduced from a comparative evolutionary approach, were mutated to dissect AGB1-dependent physiological functions. Analysis of the capacity of these mutants to complement well-established phenotypes of Gβ-null mutants revealed AGB1 residues critical for specific AGB1-mediated biological processes, including growth architecture, pathogen resistance, stomata-mediated leaf-air gas exchange, and possibly photosynthesis. These findings provide promising new avenues to direct the finely tuned engineering of crop yield and traits.
Highlights
The heterotrimeric G-protein complex provides signal amplification and target specificity
Through bioinformatic and phylogenetic analysis, we predicted that several surface residues are requisite for specific binding of AGB1 to one of its effectors, and we validated this prediction using an in vitro enzymatic assay (Friedman et al, 2011)
We examined the functional complementation of Gb-null mutant phenotypes (Table S1) by transforming agb1-2 with mutated AGB1 variants, with the expectation of mapping candidate surface residues within interfaces between AGB1 and its unknown effectors involved in specific physiological processes
Summary
The heterotrimeric G-protein complex provides signal amplification and target specificity. Analysis of the capacity of these mutants to complement well-established phenotypes of Gb-null mutants revealed AGB1 residues critical for specific AGB1-mediated biological processes, including growth architecture, pathogen resistance, stomata-mediated leaf-air gas exchange, and possibly photosynthesis. These findings provide promising new avenues to direct the finely tuned engineering of crop yield and traits. More recent data suggest a link between AGB1-mediated P. cucumerina resistance and the modification of cell wall architecture (Delgado-Cerezo et al, 2012) Another important agricultural trait regulated by the heterotrimeric G protein is transpiration efficiency, which is increased in gpa mutants (Nilson and Assmann, 2010). Not surprisingly, signal transduction pathways of several phytohormones and environmental stimuli are altered in G-protein mutants, including
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