Evidence that the Arabidopsis thaliana 3-hydroxy-3-methylglutaryl-CoA reductase 1 is phosphorylated at Ser577 in planta .

3-Hydroxy-3-methylglutaryl-CoA reductase (HMGR) is an essential enzyme in the mevalonate pathway. In higher plants, mevalonate pathway involves in the production of precursor for isoprenoids biosynthesis, including essential components for cell functions. Previously, we confirmed that the HMGR1S (AtHMGR1S) is phosphorylated at S577 by the combination of sucrose non-fermenting related kinase-1 (SnRK1) and geminivirus rep-interacting kinase-1 (GRIK1) . However, even in quantitative phosphoproteomics studies that were directed to find SnRK1 target substrates, AtHMGR1S phosphorylation at S577 has never been detected . In this study, we expressed AtHMGR1S as a C-terminal FLAG-fusion protein in mutant to confirm its phosphorylation . Our results provide the first direct evidence that AtHMGR1S is phosphorylated at S577 . Moreover, phosphatase inhibitors treatment to the seedlings induced AtHMGR1S phosphorylation at sites other than S577, suggesting the presence of a novel HMGR regulatory mechanism .