title: Growth attenuation under saline stress is mediated by the heterotrimeric G protein complex.
abstract: BACKGROUND
  Plant growth is plastic, able to rapidly adjust to fluctuation in environmental conditions such as drought and salinity. Due to long-term irrigation use in agricultural systems, soil salinity is increasing; consequently crop yield is adversely affected. It is known that salt tolerance is a quantitative trait supported by genes affecting ion homeostasis, ion transport, ion compartmentalization and ion selectivity. Less is known about pathways connecting NaCl and cell proliferation and cell death. Plant growth and cell proliferation is, in part, controlled by the concerted activity of the heterotrimeric G-protein complex with glucose. Prompted by the abundance of stress-related, functional annotations of genes encoding proteins that interact with core components of the Arabidopsis heterotrimeric G protein complex (AtRGS1, AtGPA1, AGB1, and AGG), we tested the hypothesis that G proteins modulate plant growth under salt stress.
  
  
  RESULTS
  Na+ activates G signaling as quantitated by internalization of Arabidopsis Regulator of G Signaling protein 1 (AtRGS1). Despite being components of a singular signaling complex loss of the Gβ subunit (agb1-2 mutant) conferred accelerated senescence and aborted development in the presence of Na+, whereas loss of AtRGS1 (rgs1-2 mutant) conferred Na+ tolerance evident as less attenuated shoot growth and senescence. Site-directed changes in the Gα and Gβγ protein-protein interface were made to disrupt the interaction between the Gα and Gβγ subunits in order to elevate free activated Gα subunit and free Gβγ dimer at the plasma membrane. These mutations conferred sodium tolerance. Glucose in the growth media improved the survival under salt stress in Col but not in agb1-2 or rgs1-2 mutants.
  
  
  CONCLUSIONS
  These results demonstrate a direct role for G-protein signaling in the plant growth response to salt stress. The contrasting phenotypes of agb1-2 and rgs1-2 mutants suggest that G-proteins balance growth and death under salt stress. The phenotypes of the loss-of-function mutations prompted the model that during salt stress, G activation promotes growth and attenuates senescence probably by releasing ER stress.
authors.forename: Alejandro C
authors.initials: AC
authors.lastname: Colaneri
authors.forename: Meral
authors.initials: M
authors.lastname: Tunc-Ozdemir
authors.forename: Jian Ping
authors.initials: JP
authors.lastname: Huang
authors.affiliation: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill NC, 27599, USA. alan_jones@unc.edu.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jones
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D063990:Gene Ontology; D005947:Glucose / Q000494:pharmacology; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D008353:Mannitol / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D009997:Osmotic Pressure / Q000187:drug effects; D010641:Phenotype; D063245:Plant Development / Q000187:drug effects*; D011485:Protein Binding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D021122:Protein Subunits / Q000378:metabolism; D055049:Salt Tolerance / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D012964:Sodium / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects*
chemical_list: D029681:Arabidopsis Proteins; D021122:Protein Subunits; D008353:Mannitol; D012965:Sodium Chloride; D012964:Sodium; D020962:Heterotrimeric GTP-Binding Proteins; D005947:Glucose