Involvement of glyoxalases and glutathione reductase in conferring abiotic stress tolerance to Jatropha curcas L.

Abstract

In the current study, we characterized three crucial enzymes, glyoxalase I, II (JcGLYI, JcGLYII) and glutathione reductase (JcGR) that are known to play key role in metabolite degradation and oxidative stress tolerance. Methylglyoxal (MG) produced during abiotic stress causes severe damage to plants and glyoxalases along with glutathione (GSH) detoxify MG to non-toxic compounds. Our transcriptome analysis of Jatropha revealed the presence of putative JcGLYI, JcGLYII and JcGR. The Conserved Domain Database (CDD) analysis of JcGLYI showed two active sites for metal and glutathione binding while JcGLYII had β-lactamase domain. The three corresponding genes were heterologously expressed in E.coli BL-21(DE3) individually and the purified proteins were analysed through MALDI-TOF analysis. JcGLYI, II and JcGR showed specific activity of 1.08, 0.913 and 0.12 mmol min−1 mg−1 protein with hemithioacetal, S-D-lactoyl glutathione (SLG) and oxidised glutathione (GSSG) as substrates respectively. JcGLYI sequence alignment, phylogenetic analysis together with its enzyme kinetics indicated its Ni2+ specificity. Bacterial and yeast growth curves confirmed their protective role against PEG (5%), NaCl (200 mM) and MG (5 mM). The mRNA expression levels and enzyme activities of these three important enzymes in leaves and roots under drought, salt and combined stress conditions along with total glutathione content were assessed. Our results clearly demonstrated the expression and activities of GLYI and GLYII in corroboration with GR under the drought and salt stress which actively metabolised harmful MG into less toxic compounds, suggesting their protective role in abiotic stress tolerance in J. curcas.