Methyl jasmonate and β-cyclodextrin shake hands to boost withaferin A production from the hairy root culture of Withania somnifera

For the first time, an effort was made to study potential effects of leaf and stem explants of three genotypes of Withania somnifera (L.) Dunal (i.e., G1, G2, and G3) for hairy root induction via applying four strains of Agrobacterium rhizogenes (i.e., LBA 9402, A4, and ATTC 15834) and A. tumefaciens (i.e., C58C1). Furthermore, to improve withaferin A production, the superior treatment was subjected to elicitation with β-cyclodextrin (β-CD) and methyl jasmonate (MeJA) (alone or in combination) after 48 h exposure time. Among 24 treatments resulted from multiplying three main factors, the superiority of “G3/ATCC/LEAF” treatment was verified in terms of “ induction rate ” and “ number of induced roots ” alongside “ growth curve ”, and utilized subsequently for elicitation assay. The highest amounts of withaferin A were quantified for both hairy root sample groups of “0.5 mM β-CD + 100 µM MeJA” (9.57 mg/g DW) and “5.0 mM β-CD + 100 µM MeJA” (17.45 mg/g DW), with the fold change values of 6.84-fold and 12.46-fold compared to control, respectively. Similarly, either individual or simultaneous applications of both elicitors, apart from some fluctuations, could overall boost transcript magnitudes of the four selected genes of HMGR , SQS , SMT-1 , and SDS/CYP710A involved in withanolides biosynthetic pathway as compared with control. The results, altogether, demonstrated the superiority of leaf explant and Agropine-type strain of ATCC 15834 for hairy root induction, followed by synergistic effect of exogenous application of both MeJA and β-CD on the in vitro production of withaferin A, and possibly other types of withanolides in the hairy root culture of W. somnifera .