Abstract
In higher plants, isoprenoids are synthesized via mevalonate pathway and non-mevalonate pathway. Sterols are formed in cytoplasm via the former pathway. The key enzyme on mevalonate pathway is 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR). HMGR is regulated on the transcriptional and post-translational level. HMGR is inactivated by AMP-activated protein kinase (AMPK) in mammals. In plants, however, it is not known whether HMGR is regulated by AMPK-homologous kinases (SnRK) in vivo. Therefore, we analyzed Arabidopsis SnRKs, Akin10, Akin11 and Akin12. Kinase assay using HMGR C-terminal peptide as a substrate revealed that Akin10 and Akin11 could phosphorylate HMGR but Akin12 could not. To determine organs where Akin10, Akin11 and Akin12 are expressed, we examined the RT-PCR analysis. Akin10 and Akin11 are expressed ubiquitously. On the other hand, Akin12 is expressed in immature siliques. These results suggested that Akin10 and/or Akin11 are functional HMGR kinases. Now, we are screening and analyzing insertion mutants of these genes.
