Dissection of the relationship between RACK1 and heterotrimeric G-proteins in Arabidopsis.
Mammalian receptor for activated C kinase 1 (RACK1) is a versatile scaffold protein, playing regulatory roles in multiple signal transduction pathways. Moreover, RACK1 interacts with the heterotrimeric G-proteins (G-proteins) and regulates some specific functions of Gbetagamma. Although the protein sequences of both RACK1 and G-proteins are highly conserved in Arabidopsis, their relationship remains elusive. Here we provide genetic and biochemical evidence that Arabidopsis RACK1 and G-proteins may act through a mechanism that is distinct from their counterparts in mammals. Loss-of-function alleles of RACK1A (the most abundantly expressed RACK1 gene in Arabidopsis) do not appear to share morphological and developmental phenotypes with loss-of-function alleles of GPA1 (encoding the sole Galpha in Arabidopsis) or AGB1 (encoding the sole Gbeta in Arabidopsis). The analysis of gpa1 rack1a and agb1 rack1a double mutants suggested that the effect of RACK1A on morphological and developmental traits may occur independently of the presence or absence of the G-protein subunits. Although both RACK1A and G-protein subunits are negative regulators of ABA responses in the ABA inhibition of early seedling development, an additive ABA hypersensitivity was observed in gpa1 rack1a and agb1 rack1a double mutants. Biochemical analysis suggested that unlike their counterparts in mammals, RACK1 may not physically interact with AGB1. Taken together, these findings revealed some fundamental differences in the relationship of RACK1 and G-proteins between Arabidopsis and mammals.
Guo
Jianjun
J
Department of Botany, University of British Columbia, BC, Canada.
Wang
Shucai
S
Wang
Junbi
J
Huang
Wei-Dong
WD
Liang
Jiansheng
J
Chen
Jin-Gui
JG
D000040:Abscisic Acid / Q000494:pharmacology; D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
C089590:AGB1 protein, Arabidopsis; D029681:Arabidopsis Proteins; C429765:GPA1 protein, Arabidopsis; D044385:GTP-Binding Protein alpha Subunits; D044387:GTP-Binding Protein beta Subunits; C515163:RACK1 protein, Arabidopsis; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D000040:Abscisic Acid; D020962:Heterotrimeric GTP-Binding Proteins