Abstract
Metabolic adjustment to changing environmental conditions, particularly balancing of growth and defense responses, is crucial for all organisms to survive. The evolutionary conserved AMPK/Snf1/SnRK1 kinases are well-known metabolic master regulators in the low-energy response in animals, yeast and plants. They act at two different levels: by modulating the activity of key metabolic enzymes, and by massive transcriptional reprogramming. While the first part is well established, the latter function is only partially understood in animals and not at all in plants. Here we identified the Arabidopsis transcription factor bZIP63 as key regulator of the starvation response and direct target of the SnRK1 kinase. Phosphorylation of bZIP63 by SnRK1 changed its dimerization preference, thereby affecting target gene expression and ultimately primary metabolism. A bzip63 knock-out mutant exhibited starvation-related phenotypes, which could be functionally complemented by wild type bZIP63, but not by a version harboring point mutations in the identified SnRK1 target sites.
Highlights
Flexibility in the regulation of gene expression is crucial for all organisms to adjust their metabolism to changing growth conditions
As SUCROSE NON-FERMENTING RELATED KINASE 1 (SnRK1) was previously reported to enhance the activity of several C/S1 group basic leucine zipper (bZIP) (Baena-Gonzalez et al, 2007 ) and was suggested to be activated under energy starvation conditions (Baena-Gonzalez and Sheen, 2008)—which could explain the observed hyper-phosphorylation of bZIP63 in extended night—we focused our further analysis on AKIN10 and AKIN11
We show that bZIP63 plays an important role in the energy starvation response and metabolic regulation
Summary
Flexibility in the regulation of gene expression is crucial for all organisms to adjust their metabolism to changing growth conditions. Under stress, available energy resources need to be balanced between defense and growth. The SUCROSE NON-FERMENTING RELATED KINASE 1 (SnRK1) in plants and its orthologs, the sucrose-non-fermenting 1 (Snf1) kinase in yeast and the AMP-dependent protein kinase (AMPK) in mammals, are well-known and crucial master regulators of energy homeostasis. SnRK1 is involved in the regulation of plant metabolism, development, and stress response (Polge and Thomas, 2007; Baena-Gonzalez and Sheen, 2008), Snf is required for the
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