MAPK mediates NO/cGMP-induced GABA accumulation in soybean sprouts

Abstract

The effects of nitric oxide (NO)-guanosine 3‘,5‘-cyclic monophosphate (cGMP) on UV-B stress-induced γ-aminobutiric acid (GABA) accumulation, and the influences of mitogen-activated protein kinase (MAPK) on NO/cGMP-induced GABA accumulation under UV-B stress in soybean sprouts were investigated. The sprouts were treated with donors and inhibitors of NO and cGMP as well as MAPK inhibitor. The results showed that NO, with cGMP/PKG as a second messenger, stimulated GABA accumulation under UV-B treatment. Consistent with the elevation in GABA content, the increment of gene and protein expression and activity of diamine oxidase (DAO) and amino aldehyde dehydrogenase (AMADH) in response to 8-Br-cGMP (cGMP analog) and sodium nitroprusside (SNP) (exogenous NO donor) was also observed. Therefore, NO/cGMP mediates UV-B radiation-induced GABA accumulation in soybean sprouts. What's more, NO, with cGMP/PKG as a second messenger, activated gene and protein expression of MAPK under UV-B treatment. MAPK up-regulated gene and protein expression and activity of DAO and AMADH, and subsequently induced GABA accumulation. Overall, MAPK mediated NO/cGMP/PKG-stimulated GABA biosynthesis in soybean sprouts.