Fungal elicitors increase cell biomass, pyrroloquinazoline alkaloids production and gene expression levels of biosynthetic pathways in Adhatoda vasica Nees cell cultures

Adhatoda vasica Nees (Fam. - Acanthaceae) is used in the treatment of cold, cough, chronic bronchitis, and asthma. The plant species contain vasicine, vasicinone, 2-acetyl benzyl amine, adhatodine, vasicinolone, deoxyvasicinone, and vasicine acetate. To examine the effects of fungal elicitors on the production of pyrroloquinazoline alkaloids, five fungal elicitors (Alternaria alternata, Rhizoctonia solani, Colletotrichum gloeosporioides, Colletotrichum capsica, and Puccinia thwaitesii) were used. Four concentrations (2.5, 5.0, 10, and 20 %) of 5 fungal elicitors were added in the MS culture medium. The concentrations were designed to observe their effects (minimal to maximal) on growth and production of alkaloids in cell cultures. The seedlings of this species were transferred onto Murashige and Skoog medium containing IAA (1.5 mg/L) and BA (1.0 mg/L). The maximum quantity of vasicine (1.25 ± 0.023 %; p < 0.001) was recorded in 6 weeks old callus. The quantity of vasicine was lower in callus (1.25 ± 0.023 %; p < 0.001) than aerial parts (6.64 ± 0.034 %; p < 0.01) and roots (5.97 ± 0.097 %; p < 0.01). Alternaria alternata (10 %) increased the growth of cell biomass as well as anthranilate synthase and anthranilate N-methyl transferase activities. Similarly, Alternaria alternata showed maximum increase in the production of vasicine whereas other elicitors displayed moderate increase in alkaloid production. The expression quantities of 10 genes, involved in pyrroloquinazoline alkaloids biosynthesis, were determined in this study. The maximum expression level (11.38-fold) of anthranilate synthase was observed in elicited cells treated with A. alternata. The study results suggest widespread use of fungal elicitors in increasing the production of secondary metabolites as well as gene expression levels in plant cell cultures.