In vitro Bio-elicitation of plumbagin-an important biomolecule, employing Serendipita indica and Rhizobium rhizogenes in Plumbago zeylanica

Abstract

Plumbagozeylanica (Chitrak) is a medicinal shrub native to Southeast Asia. The current demand for P. zeylanica roots in the herbal drug market is explicitly met by the collections from natural habitats, due to which the plant is being overexploited. The development of in vitro green technology and the elicitation of important secondary metabolites are imperative for the sustainability of plant species. The present investigation highlights the enhancement of the plumbagin content employing biotic elicitors, namely Serendipita indica and Rhizobium rhizogenes. Co-cultivation of P.zeylanica shoots with S. indica- a beneficial endophytic fungus, resulting in an increased shoot (1.1 ± 0.03^a -fold) and root fresh weight (9.1 ± 0.4^a-fold); and plumbagin content (140.3 ± 2.2^a %). Besides this, in another experimental set, hairy roots were induced from leaf explants of P.zeylanica via co-cultivation with R. rhizogenes (A4). Such roots emerged after 7-d exhibiting a maximum transformation efficiency of 68.3 ± 2.1^a % on MS+ 50 μM acetosyringone. The putative transformants were screened through PCR of root locus (rol A, B and C) genes. Eight hairy root lines (R) were established and their morphological (relative growth rate, branching pattern and surface topography) and biochemical (plumbagin) parameters were analyzed. Of all the hairy root lines, R5 accumulated maximum plumbagin content, i.e. 889.8 ± 6.5^a % and showed a maximum growth index (0.86 ± 0.001^a). An increased plumbagin level was seen in the order of R5 >R3 >R8 >R6 >R9 >R7 >R4 >R1. These two approaches represent non-toxic and eco-friendly strategies for enhancing plumbagin. To our knowledge, this is the first documented report on S. indica co-cultivation for plumbagin elicitation in P. zeylanica.