Interaction between SNF1-related kinases and a cytosolic pyruvate kinase of potato.

SNF1-related protein kinases (SnRKs) are widely conserved in plants. Previous studies have shown that members of the SnRK1 subfamily phosphorylate and inactivate at least four important plant metabolic enzymes: 3-hydroxy-3-methylglutaryl-CoA reductase, sucrose phosphate synthase, nitrate reductase, and trehalose phosphate synthase 5. In this paper, we demonstrate that two SnRK1 proteins of potato, PKIN1 and StubSNF1, interact with a cytosolic pyruvate kinase (PK(c)) of potato in a yeast two-hybrid assay. The interacting domain of PK(c) is located in its C-terminal region and contains the putative SnRK1 recognition motif ALHRIGS(500)ASVI. Our results indicate that both SnRK1s influence PK(c) activity in vivo. Antisense repression of SnRK1s alters the intensity and light/dark periodicity of PK activity in leaves. However, the differences between PK activity curves in antisense PKIN1 and antisense StubSNF1 lines indicated that the function of the two kinases is not identical in potato.