Figure 4.

SNRK1 plays a central role in sensing nutrient deprivation and stress to promote catabolism but inhibit anabolism and growth. The SNRK1 complex is composed of catalytic a (KIN10/11) and regulatory β and βγ subunits. SNRK1 is activated by darkness, stress, starvation, hypoxia, and SNAKs but inhibited by sugars, metabolites, and FLZ repressors. SNRK1 phosphorylation positively (orange text) or negatively (blue text) regulates targets in broad biological processes. The catalytic a subunits (KIN10/11) can translocate to the nucleus to phosphorylate various TFs. KIN10 represses EIN3, MYC2, WRI1, IDD8, and PIF4 but activates FUS3, bZIP63, and SPCH. SNRK1 also phosphorylates and inhibits cytosolic enzymes, including SPS, NR, TPS7/8/9, and HMGR; translation regulators ISO4E, ISO4G, and ELF4E; and other signaling proteins in various biological responses. SNRK1 antagonizes TOR complex signaling by phosphorylating RAPTOR. Abbreviations: ABA, abscisic acid; ABI1, ABA INSENSITIVE1; ATG1, AUTOPHAGY RELATED1; bZIP, BASIC LEUCINE ZIPPER; EIN3, ETHYLENE INSENSITIVE3; ELF4E, EUKARYOTIC TRANSLATION INITIATION FACTOR 4E; F2KP, fructose-2,6-bisphosphatase; FLZ, FCS-LIKE ZINC FINGER; FUS3, FUSCA3; G1P, glucose 1-phosphate; G6P, glucose 6-phosphate; HMGR, 3-HYDOXY-3-METHYLGLUTARYL–COA REDUCTASE; IDD8, INDETERMINATE DOMAIN8; KIN10/11, KINASE10/11; MPK, MITOGEN-ACTIVATED PROTEIN KINASE; NR, NITRATE REDUCTASE; P, phosphorylation; PIF4, PHYTOCHROME INTERACTING FACTOR4; PP2CA, PROTEIN PHOSPHATASE 2CA; PTP, PROTEIN TYROSINE PHOSPHATASE; RAPTOR, REGULATORY-ASSOCIATED-PROTEIN-OF-MTOR1; SNAK, SNRK1-ACTIVATING KINASE; SNRK1, SNF1-RELATED KINASE1; SPCH, SPEECHLESS; SPS, SUCROSE PHOSPHATE SYNTHASE; T6P, trehalose 6-phosphate; TF, transcription factor; TOR, TARGET OF RAPAMYCIN; TPS, T6P SYNTHASE; UDP, uridine diphosphate; WRI1, WRINKLED1.