Are SnRK1 Plant Protein Kinases Distinctively Regulated by Metabolites Under Light/Dark Conditions?

C.V. PIATTONI; A.A. IGLESIAS; S.C. HUBER

Potrero de los Funes

Congreso; XLVII Reunión Anual de SAIB; 2011

ARE SnRK1 PLANT PROTEIN KINASES DISTINCTIVELY REGULATED BY METABOLITES UNDER LIGHT/DARK CONDITIONS? Piattoni CV , Iglesias AA , Huber SC . 1 2 IAL, UNL-CONICET, Santa Fe, Argentina. USDA-ARS, University of Illinois, Urbana-Champaign, IL, USA.  SnRK1s are plant protein kinases related to yeast SNF1 and mammalian AMPK. These kinases are hetero-oligomeric proteins of catalytic ( _) and non-catalytic (_ and _) subunits that would have roles in regulation and targeting. SnRK1s play key roles as major integrators of energy signaling, growth, and carbon and nitrogen metabolism. Previous works have shown that SnRK1 activity could be regulated by Glc6P, Tre6P and Rib5P depending on the plant and tissue involved. We wondered if regulation of SnRK1 by different metabolites could be related with the trophic characteristics and/or the metabolic state of the plant tissue. In this work we purified SnRK1 kinases from Arabidopsis seedlings grown under light or dark conditions and we characterized its regulation by different metabolites. Rib5P and Rul5P behaved as strong inhibitors of the SnRK1 purified from seedlings grown under light but not under dark conditions. Characterization of SnRK1 inhibition suggests that Rib5P ( I ~2 mM) and Rul5P (I 0.5 0.5~100 μM) could act as competitive inhibitors respect to ATP. Several lines of evidence suggest that inhibition by Rib5P is not the result of ATP consumption, but the potential for this artifact remains to be unequivocally ruled out. We hypothesize that differential regulation could be related with changes in SnRK1 subunit gene expression patterns of the several coding genes.