Shen, Wei , Reyes, Maria , Hanley-Bowdoin, Linda .
Activation of the Arabidopsis Protein Kinase SnRK1 by GRIK1 and GRIK2.
Protein kinases play critical signaling roles in both plant development and biotic and abiotic stress responses. We showed previously that two closely related Arabidopsis protein kinases, GRIK1 and GRIK2, interact with geminivirus AL1 proteins and their protein levels are substantially increased upon viral infection. GRIK1 and GRIK2 belong to a loose protein kinase family that includes yeast SAK1, TOS3 and ELM1 and mammalian CaMKKs and LKB1. These kinases activate their downstream kinases SNF1 and AMPK, respectively, through activation loop threonine phosphorylation. In this study, we used recombinant proteins to show that GRIK1 and GRIK2 also activate the autophosphorylation activity of Arabidopsis SnRK1.1 and SnRK1.2, the plant homologs of SNF1/AMPK, by activation loop threonine phosphorylation. Because SnRK1s are important plant nutrient and energy metabolism regulators, our results suggest that regulation of plant nutrient metabolism is altered by viral infection. Interaction of GRIK and AL1, an early expressed viral protein, may change SnRK1 activities that affect the nature and distribution of the cellular nutrient state to facilitate establishment of virus infection. On the other hand, SnRK1 has been shown to be required for plant resistance to geminivirus infection and that the geminivirus AL2/L2/C2 proteins, which are expressed later during infection, interact with and inhibit the SnRK1 activity. Thus, our results are also consistent with GRIK1 and GRIK2 acting later to counter viral anti-defense mechanisms.
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1 - North Carolina State University, Biochemistry, Campus Box 7622, Raleigh, NC, 27695-7622, U.S.A.
2 - North Carolina State University, Biochemistry
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM