Inhibition of SNF1-Related Protein Kinase1 Activity and Regulation of Metabolic Pathways by Trehalose-6-Phosphate    

Abstract

Trehalose-6-phosphate (T6P) is a proposed signaling molecule in plants, yet how it signals was not clear. Here, we provide evidence that T6P functions as an inhibitor of SNF1-related protein kinase1 (SnRK1; AKIN10/AKIN11) of the SNF1-related group of protein kinases. T6P, but not other sugars and sugar phosphates, inhibited SnRK1 in Arabidopsis (Arabidopsis thaliana) seedling extracts strongly (50%) at low concentrations (1-20 mM). Inhibition was noncompetitive with respect to ATP. In immunoprecipitation studies using antibodies to AKIN10 and AKIN11, SnRK1 catalytic activity and T6P inhibition were physically separable, with T6P inhibition of SnRK1 dependent on an intermediary factor. In subsequent analysis, T6P inhibited SnRK1 in extracts of all tissues analyzed except those of mature leaves, which did not contain the intermediary factor. To assess the impact of T6P inhibition of SnRK1 in vivo, gene expression was determined in seedlings expressing Escherichia coli otsA encoding T6P synthase to elevate T6P or otsB encoding T6P phosphatase to decrease T6P. SnRK1 target genes showed opposite regulation, consistent with the regulation of SnRK1 by T6P in vivo. Analysis of microarray data showed up-regulation by T6P of genes involved in biosynthetic reactions, such as genes for amino acid, protein, and nucleotide synthesis, the tricarboxylic acid cycle, and mitochondrial electron transport, which are normally down-regulated by SnRK1. In contrast, genes involved in photosynthesis and degradation processes, which are normally up-regulated by SnRK1, were down-regulated by T6P. These experiments provide strong evidence that T6P inhibits SnRK1 to activate biosynthetic processes in growing tissues.

Acclimation of metabolism to light in Arabidopsis thaliana: the glucose 6‐phosphate/phosphate translocator GPT2 directs metabolic acclimation

“…2006) and has been shown to inhibit SnRK1 in vitro (Zhang et al . 2009; Delatte et al . 2011; Nunes et al .…”

The Energy-Signaling Hub SnRK1 Is Important for Sucrose-Induced Hypocotyl Elongation

“…We studied hypocotyl elongation in transgenic Arabidopsis where KIN10 activity was manipulated by overexpressing the catalytic subunit of KIN10 (KIN10-ox; Baena-González et al, 2007). Although KIN10 activity is regulated posttranslationally by Tre6P (Zhang et al, 2009), KIN10 overexpression alone alters the abundance of energy-response transcripts in protoplasts (Baena-González et al, 2007). We used KIN10 overexpression rather than knockouts, because KIN10/11 double knockouts disrupt pollen production and are lethal (Zhang et al, 2001;BaenaGonzález et al, 2007).…”

“…Both SnRK1-and hexokinasemediated sugar signaling involve specific sugars functioning as signaling molecules that provide cellular information concerning sugar availability. For example, SnRK1 activity is thought to be regulated by trehalose-6-P (Tre6P), whose concentration tracks the cellular concentration of Suc (Lunn et al, 2006;Zhang et al, 2009;Nunes et al, 2013aNunes et al, , 2013bYadav et al, 2014). Tre6P is synthesized from UDP Glc and Glc-6-P, which are derived from mobilized and transported Suc, and also directly from photosynthesis.…”

“…Of 11 TPS homologs encoded by the Arabidopsis genome, TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) synthesizes Tre6P in plants (Gómez et al, 2010;Vandesteene et al, 2010), and TPS2 and TPS4 are catalytically active in yeast complementation assays (Delorge et al, 2015). Tre6P is believed to regulate SnRK1-mediated signaling by suppressing the activity of SNF1-RELATED PRO-TEIN KINASE1.1 (KIN10/AKIN10/SnRK1.1), which is a catalytic subunit of SnRK1 that is fundamental to the signaling role of SnRK1 (Baena-González et al, 2007;Zhang et al, 2009;Nunes et al, 2013aNunes et al, , 2013b.…”

Nitrogen regulates CRY1 phosphorylation and circadian clock input pathways

“…14 Arabidopsis AMPKa1 shows inhibitory responses to sugar metabolites, especially the trehalose-6-phosphate (T6P). 15 But no clear correction between plant SnRK family proteins and sugar signaling or other nutritional signaling in plant cells has been identified. Here we find that the high level of AMP under the high N condition activates Arabidopsis AMPKa1.…”