AUTHOR=Shukla Namita , Singh Deepti , Tripathi Arpita , Kumari Poonam , Gupta Rahul Kumar , Singh Shiwangi , Shanker Karuna , Singh Akanksha 

TITLE=Synergism of endophytic Bacillus subtilis and Klebsiella aerogenes modulates plant growth and bacoside biosynthesis in Bacopa monnieri

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.896856

DOI=10.3389/fpls.2022.896856

ISSN=1664-462X

ABSTRACT=<p><italic>Bacopa monnieri</italic> is the main source of pharmaceutically important bacosides; however, the low content of these molecules <italic>in planta</italic> remains a limiting factor for fulfilling the industrial requirement. The accumulation of secondary metabolites can be enhanced in plants upon inoculation with endophytes. In this study, we isolated and analyzed the culturable endophytes associated with different plant parts. By analyzing their impact on plant growth parameters (<italic>in vitro</italic> and <italic>in vivo</italic>) and Bacoside A content, we found few candidates which increased bacoside accumulation significantly. Finally, two promising endophytes namely <italic>Bacillus subtilis</italic> (OK070745) and <italic>Klebsiella aerogenes</italic> (OK070774) were co-cultivated with <italic>B. monnieri</italic> cuttings singly and in combination mode to clarify their effect on bacoside biosynthesis and their accumulation in <italic>B. monnieri</italic> shoot. Consortium-inoculated plants significantly enhanced the plant biomass and Bacoside A content with respect to single inoculation. The results of real-time quantitative (RT-PCR) revealed significant accumulation of bacoside biosynthetic pathway transcripts (<italic>HMGCR, PMVK, FDPS, SQS</italic>, and β<italic>-AS)</italic> in the case of plants inoculated with microbial combination, while the single inoculation of <italic>B. subtilis</italic> diverted the plant’s machinery toward the synthesis of phenylpropanoid genes like <italic>CCR, CAD, CHS</italic>, and <italic>HST.</italic> In addition, higher expression of <italic>MYB 2</italic> and <italic>WRKY 1</italic> transcription factors in combinational treatment points out their probable role in better physiological and developmental processes. Altogether, this is the first study on <italic>B. monnieri</italic>-endophyte interaction showing improvement in the accumulation of bacoside A by modulating various genes of metabolic pathway and thus suggests an effective “green approach” for augmenting <italic>in planta</italic> production of pharmaceutically important bacosides.</p>