Abstract
Not much is known about the mechanism of endophyte-mediated induction of secondary metabolite production in Catharanthus roseus. In the present study two fungal endophytes, Curvularia sp. CATDLF5 and Choanephora infundibulifera CATDLF6 were isolated from the leaves of the plant that were found to enhance vindoline content by 229–403%. The isolated endophytes did not affect the primary metabolism of the plant as the maximum quantum efficiency of PSII, net CO2 assimilation, plant biomass and starch content of endophyte-inoculated plants was similar to endophyte-free control plants. Expression of terpenoid indole alkaloid (TIA) pathway genes, geraniol 10-hydroxylase (G10H), tryptophan decarboxylase (TDC), strictosidine synthase (STR), 16-hydoxytabersonine-O-methyltransferase (16OMT), desacetoxyvindoline-4-hydroxylase (D4H), deacetylvindoline-4-O-acetyltransferase (DAT) were upregulated in endophyte-inoculated plants. Endophyte inoculation upregulated the expression of the gene for transcriptional activator octadecanoid-responsive Catharanthus AP2-domain protein (ORCA3) and downregulated the expression of Cys2/His2-type zinc finger protein family transcriptional repressors (ZCTs). The gene for the vacuolar class III peroxidase (PRX1), responsible for coupling vindoline and catharanthine, was upregulated in endophyte-inoculated plants. These endophytes may enhance vindoline production by modulating the expression of key structural and regulatory genes of vindoline biosynthesis without affecting the primary metabolism of the host plant.
Highlights
In bioactive secondary metabolite production in present fermentation practices through the use of fungal endophytes is the instability of the expression of genes involved in the biosynthesis of the desired metabolite(s)
A total of seven fungal endophytes were isolated from C. roseus genotype Dhawal and their potential to enhance vindoline content was examined in both genotypes Dhawal and Prabal
High-performance liquid chromatography (HPLC) analysis of leaves of CATDLF5- and CATDLF6-inoculated plants was performed, and vindoline content was compared with two types of controls–(i) endophyte-free control [C] and (ii) natural control [NC] plants containing the naturally present endophytes
Summary
In bioactive secondary metabolite production in present fermentation practices through the use of fungal endophytes is the instability of the expression of genes involved in the biosynthesis of the desired metabolite(s). Due to complicated structures of these alkaloids, their chemical synthesis in large scale is not economically feasible[25,26] Diverse approaches such as transgenic generation, tissue culture practices, phytohormone treatments are being attempted to achieve enhanced production of important TIAs. Most of the genes that encode enzymes for TIA biosynthesis and regulatory components such as transcriptional activators and repressors have been identified[20,27,28,29,30,31] (Fig. 1). Efforts were made to identify and characterize fungal endophytes capable of enhancing the vindoline content in C. roseus and to study the possible mechanism involved Towards this end, fungal endophytes were isolated from alkaloid-rich genotype The idea was to explore the role, if any, of endophytes isolated from an alkaloid-rich genotype in improving the alkaloid content of low-alkaloid genotypes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
