Enhanced stress tolerance in transformed ajuga bracteosa wall. Ex benth. regenerants by upregulated gene expression of metabolic pathways

Abstract

The rol oncogenes of Agrobacterium rhizogenes enhance the production of medicinally important compounds in plants and provide a first barrier against the overproduction of reactive oxygen species during biotic and abiotic stress. This study was designed to evaluate the expression of genes involved in biosynthetic pathways and their impact on metabolic contents and environmental stress tolerance in regenerated Ajuga bracteosa Wall. ex Benth. After successful transformation, real-time quantitative PCR confirmed the increased expression (1.94–6.59-fold) of HMGR, HDS, FDS, PAL, and TTG1 genes in transgenic lines. Furthermore, GC-MS coupled with principal component analysis revealed diverse concentrations of 97 metabolites in A. bracteosa. Transgenic lines showed greater survival under multiple stresses. This was revealed by significant chlorophyll content (8.13–21 µmoles/m2), higher quantum efficiency of PSII (Fv/Fm), and the performance index (PIabs) value. Similarly, catalase and peroxidase enzyme activities were enhanced during extreme drought (300–400 mM mannitol) and salinity (150–200 mM NaCl) conditions, compared to untransformed control. Wild type control plant leaves were completely necrotized by Aspergillus fumigatus (FCBP 66) and Fusarium solani (FCBP 0291), whereas transformed leaves had improved antifungal resistance. In conclusion, our data suggest that rolABC genes have a significant impact on the synthesis of metabolites involved in enhancing multistress tolerance in A. bracteosa.