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 mu moles/m(2)), higher quantum efficiency of PSII (F-v/F-m), 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.
Highlights
Plants are prone to a wide variety of environmental stresses due to their sessile and restricted nature
Phenotype and molecular analysis of the transgenic plants Nonchimeric A. bracteosa plants were regenerated from transgenic hairy roots in this study
The phenotype of regenerated plants was consistent with the previously reported data characteristic of A. bracteosa derived from transgenic hairy roots (Kayani et al, 2016a), i.e. they had a large number of curled leaves and short internodes with a bushy appearance
Summary
Plants are prone to a wide variety of environmental stresses due to their sessile and restricted nature. Tissue or organ specificity for the synthesis and translocation of certain groups of metabolites hinders the development of hairy root cultures (Isah, 2019). To solve this problem, Kayani et al (2016a) regenerated A. bracteosa plants from transgenic hairy roots and found improved production of phytoecdysteroids in regenerants. The correlation of rol genes to cope with stresses has not been observed in medicinal plants We explored these issues by using the intact regenerated plants from the transgenic hairy root lines of A. bracteosa and suggest a possible impact of rolABC on the expression of some of the genes involved in the biosynthetic pathways of therapeutically important secondary metabolites. We tried to explain the possible involvement of the rol genes in coping with stress through up- and downregulation of the genes involved in secondary metabolism
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