The plastid protein THYLAKOID FORMATION1 and the plasma membrane G-protein GPA1 interact in a novel sugar-signaling mechanism in Arabidopsis.
Mutations in genes encoding components of the heterotrimeric G-protein complex were previously shown to confer altered sensitivity to increased levels of D-glucose. This suggests that G-protein coupling may be a novel sugar-signaling mechanism in Arabidopsis thaliana. THYLAKOID FORMATION1 (THF1) is here demonstrated in vivo as a Galpha interaction partner that functions downstream of the plasma membrane-delimited heterotrimeric G-protein (GPA1) in a D-glucose signaling pathway. THF1 is a plastid protein localized to both the outer plastid membrane and the stroma. Contact between root plastidic THF1 and GPA1 at the plasma membrane occurs at sites where the plastid membrane abuts the plasma membrane, as demonstrated by Förster resonance energy transfer (FRET). A probable role for THF1 in sugar signaling is demonstrated by both biochemical and genetic evidence. Root growth in the thf1-1 null mutant is hypersensitive to exogenous D-glucose, and THF1-overexpressing roots are resistant to inhibition of growth rate by high D-glucose. Additionally, THF1 levels are rapidly degraded by D-glucose but not L-glucose. The interaction between THF1 and GPA1 has been confirmed by in vitro and in vivo coimmunoprecipitation, FRET analysis, and genetic epistasis and provides evidence of a sugar-signaling mechanism between plastids and the plasma membrane.
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Jirong
J
Huang
J Philip
JP
Taylor
Jin-Gui
JG
Chen
Joachim F
JF
Uhrig
Danny J
DJ
Schnell
Tsuyoshi
T
Nakagawa
Kenneth L
KL
Korth
Alan M
AM
Jones
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000033:anatomy & histology / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D018519:Meristem / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D018517:Plant Roots / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D018087:Plastids / Q000378:metabolism* / Q000648:ultrastructure; D025941:Protein Interaction Mapping; D016415:Sequence Alignment; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; C429765:GPA1 protein, Arabidopsis; D044385:GTP-Binding Protein alpha Subunits; D008565:Membrane Proteins; C512069:THF1 protein, Arabidopsis; D005947:Glucose