SnRK1 Isoforms AKIN10 and AKIN11 Are Differentially Regulated in Arabidopsis Plants under Phosphate Starvation

Abstract

During phosphate starvation, Snf1-related kinase 1 (SnRK1) activity significantly decreases compared with plants growing under normal nutritional conditions. An analysis of the expression of the genes encoding for the catalytic subunits of SnRK1 showed that these subunits were not affected by phosphate starvation. Transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing the AKIN10 and AKIN11 catalytic subunits fused with green fluorescent protein (GFP) were produced, and their localizations were mainly chloroplastic with low but detectable signals in the cytoplasm. These data were corroborated with an immunocytochemistry analysis using leaf and root sections with an anti-AKIN10/AKIN11 antibody. The SnRK1 activity in transgenic plants overexpressing AKIN11-GFP was reduced by 35% to 40% in phosphate starvation, in contrast with the results observed in plants overexpressing AKIN10-GFP, which increased the activity by 100%. No differences in activity were observed in plants growing in phosphate-sufficient conditions. Biochemical analysis of the proteins indicated that AKIN11 is specifically degraded under these limited conditions and that the increase in AKIN10-GFP activity was not due to the phosphorylation of threonine-175. These results are consistent with an important role of AKIN10 in signaling during phosphate starvation. Moreover, akin10 mutant plants were deficient in starch mobilization at night during inorganic phosphate starvation, and under this condition several genes were up-regulated and down-regulated, indicating their important roles in the control of general transcription. This finding reveals novel roles for the different catalytic subunits during phosphate starvation.

Changes in the Phosphoproteome and Metabolome Link Early Signaling Events to Rearrangement of Photosynthesis and Central Metabolism in Salinity and Oxidative Stress Response in Arabidopsis

“…Furthermore, it is well known that primary metabolism is repressed in Arabidopsis by AKIN10/AKIN11 but activated in AKIN10/AKIN11 knockdown plants (Baena-González et al, 2007). The silencing of AKIN10 was also related to an activation of SPS and concomitant repression of transcription factors and some protein degradation regulators (Fragoso et al, 2009). Consequently, our data indicated that short-term metabolic adaptation is performed by AKIN10/AKIN11 through direct modulation of the activity of some key metabolic enzymes.…”

Systemic Cold Stress Adaptation of Chlamydomonas reinhardtii

“…The increase of the protein biosynthesis and glycolysis pathways during the first 72 h of cold acclimation, and its later repression when CKIN1 levels are recovered give clues of its function in our experimental system. It has been reported that all of these pathways are repressed in Arabidopsis by AKIN10 (23) while activated in mutants (114). The silencing of AKIN10 was also related to an activation of sucrose-6P-synthase (SPS) and THF1 (which function was described above) and at the same time to a repression of transcription factors and some protein degradation regulators (114).…”

Regulatory Functions of SnRK1 in Stress-Responsive Gene Expression and in Plant Growth and Development

“…AtSnRK1 activity is repressed by inorganic phosphate starvation and trehalose-6-phosphate application (Fragoso et al, 2009;Zhang et al, 2009) and binds to myoinositol polyphosphate-5-phosphatase, which negatively regulates the kinase activity (Ananieva et al, 2008). AtSnRK1-activating kinases, AtSnAK1 and AtSnAK2, and AtSnRK1 establish a dynamic and reciprocal regulatory process though feedback phosphorylation (Shen et al, 2009;Crozet et al, 2010).…”