Microbial modulation of bacoside A biosynthetic pathway and systemic defense mechanism in Bacopa monnieri under Meloidogyne incognita stress

Abstract

Plant-associated beneficial microbes have been explored to fulfill the imperative function for plant health. However, their impact on the host secondary metabolite production and nematode disease management remains elusive. Our present work has shown that chitinolytic microbes viz., Chitiniphilus sp. MTN22 and Streptomyces sp. MTN14 singly as well as in combination modulated the biosynthetic pathway of bacoside A and systemic defense mechanism against Meloidogyne incognita in Bacopa monnieri. Interestingly, expression of bacoside biosynthetic pathway genes (3-Hydroxy-3-methylglutaryl coenzyme A reductase, mevalonate diphosphate decarboxylase, and squalene synthase) were upregulated in plants treated with the microbial combination in the presence as well as in absence of M. incognita stress. These microbes not only augmented bacoside A production (1.5 fold) but also strengthened host resistance via enhancement in chlorophyll a, defense enzymes and phenolic compounds like gallic acid, syringic acid, ferulic acid and cinnamic acid. Furthermore, elevated lignification and callose deposition in the microbial combination treated plants corroborate well with the above findings. Overall, the results provide novel insights into the underlying mechanisms of priming by beneficial microbes and underscore their capacity to trigger bacoside A production in B. monnieri under biotic stress.

Bacopaside N1 biosynthetic potential of endophytic Aspergillus sp. BmF 16 isolated from Bacopa monnieri

“…MTN14 singly as well as in combination revealed their modulatory effect on in planta bacoside A production. Here, the expression of bacopaside biosynthetic pathway genes (3-hydroxy-3-methylglutaryl coenzyme A reductase, mevalonate diphosphate decarboxylase, and squalene synthase) has also been shown to be upregulated in plants treated with the microbial combination (Gupta et al 2017). Our recent report also indicated the promises of plant growth promoting rhizobacteria in modulation of bacopaside content in B. monnieri (Jimtha and Radhakrishnan 2016).…”

Endophyte-Mediated Modulation of Defense-Related Genes and Systemic Resistance in Withania somnifera (L.) Dunal under Alternaria alternata Stress

“…After incubation, the leaf samples were washed with 20 mM phosphate buffer (pH 7.0) and were visualized under the microscope with excitation at 488 nm and emission at 505/30 nm (48). To detect the callose deposition, the leaves were placed in K 2 HPO 4 (150 mM; pH 9.5) containing 0.1% aniline blue for 1 h followed by washing with sterile distilled water, and the stained leaves were examined under the microscope (49).…”

Exogenous application of rutin and gallic acid regulate antioxidants and alleviate reactive oxygen generation in Oryza sativa L.

“…The reaction mixture was centrifuged at 10,000g for 5 min and the optical density was read at 663, 645, 480 and 510 nm. The total phenolic content (TPC) was calculated using gallic acid (mg per g of dried sample) as standard (Gupta et al 2017). A sodium carbonate solution (7%; 2.5 mL) and 0.5 mL of Folin Ciocalteu reagent were added to 1 mL methanolic extract of leaf tissue.…”