AKINβ1, a regulatory subunit of SnRK1, regulates organic acid metabolism and acts as a global regulator of genes involved in carbon, lipid and nitrogen metabolism

The sucrose non-fermenting-1-related protein kinase 1 (SnRK1) is a highly conserved heterotrimeric protein kinase in plants. It possesses a catalytic subunit (alpha) and two regulatory subunits (beta and gamma). The effects of altered expression of AKIN beta 1 on carbohydrate metabolism and gene expression in leaves were investigated in an Arabidopsis T-DNA insertion mutant. The contents of key intermediates in the tricarboxylic acid (TCA) cycle of the mutant leaves were markedly reduced throughout the diurnal cycle, coupled with a decrease in measurable respiration rate. Compared with the wild type, 2485 genes and 188 genes were differentially expressed in leaves of the akin beta 1 mutant in response to light and darkness, respectively. Among these, several genes exhibited very substantial decreases in expression. Notably, expression of particular isoforms of multigene families involved in malate and lipid metabolism and nitrate uptake showed decreases of 40- to 240-fold during the light period, but not during darkness. The subcellular localization of AKIN beta 1 and the regulatory function of N-myristoylation for this localization were investigated, showing that AKIN beta 1 localizes to the Golgi. A model is hypothesized to explain the effects of AKIN beta 1 on metabolism and gene expression in Arabidopsis.