Metabolic Circuits in Sap Extracts Reflect the Effects of a Microbial Biostimulant on Maize Metabolism under Drought Conditions

Abstract

The use of microbial biostimulants in the agricultural sector is increasingly gaining momentum and drawing scientific attention to decode the molecular interactions between the biostimulants and plants. Although these biostimulants have been shown to improve plant health and development, the underlying molecular phenomenology remains enigmatic. Thus, this study is a metabolomics work to unravel metabolic circuits in sap extracts from maize plants treated with a microbial biostimulant, under normal and drought conditions. The biostimulant, which was a consortium of different Bacilli strains, was applied at the planting stage, followed by drought stress application. The maize sap extracts were collected at 5 weeks after emergence, and the extracted metabolites were analyzed on liquid chromatography-mass spectrometry platforms. The acquired data were mined using chemometrics and bioinformatics tools. The results showed that under both well-watered and drought stress conditions, the application of the biostimulant led to differential changes in the profiles of amino acids, hormones, TCA intermediates, phenolics, steviol glycosides and oxylipins. These metabolic changes spanned several biological pathways and involved a high correlation of the biochemical as well as structural metabolic relationships that coordinate the maize metabolism. The hypothetical model, postulated from this study, describes metabolic events induced by the microbial biostimulant for growth promotion and enhanced defences. Such understanding of biostimulant-induced changes in maize sap pinpoints to the biochemistry and molecular mechanisms that govern the biostimulant–plant interactions, which contribute to ongoing efforts to generate actionable knowledge of the molecular and physiological mechanisms that define modes of action of biostimulants.

Effects of Date Palm Waste Compost Application on Root Proteome Changes of Barley (Hordeum vulgare L.)

“…It is well known that under stressed conditions, carbohydrates can act as osmoprotectants that remove reactive oxygen species (ROS) and stabilise cellular membranes, which can protect plants from oxidative damage [ 44 ]. Under stressed conditions, several previous studies, such as those on poplar [ 41 ], Arabidopsis [ 23 ], maize [ 45 ] and potato [ 46 ], have shown that the application of biostimulants and organic amendments increases the expression of various proteins that often participate in energy and carbohydrate metabolism. These results suggest that enzymes associated with the glycolytic pathway might assist in the intensification of glycolysis to provide energy for supporting plant growth and metabolic activities under abiotic and biotic stresses.…”

Mass Spectral Molecular Networking to Profile the Metabolome of Biostimulant Bacillus Strains

“…The microbial consortium is a commercial product—Bacstim ® 100, containing equal volumes of the above-mentioned Bacillus strains (Omnia Group Ltd., South Africa). The biostimulant activity of this microbial consortium, Bacstim ® 100, has been tested on maize plants under greenhouse conditions, where enhanced plant growth and drought tolerance was demonstrated ( Nephali et al, 2021 ; Othibeng et al, 2022 ).…”

Bacillus for Plant Growth Promotion and Stress Resilience: What Have We Learned?

“…Other mechanisms associated with enhancing stress tolerance involve triggering biological and physiological processes such as ROS detoxification mechanisms, osmoprotection, stomatal regulation, membrane stability, xylem hydraulic conductance, root zone water, and nutrient availability and metal chelation [ 99 , 100 , 101 ]. For example, recent studies by Nephali et al [ 11 ], Lephatsi et al [ 13 ] and Othibeng et al [ 102 ] revealed that the application of Bacillus consortium (a commercial biostimulant known as Bacstim ® 100) to maize plants improves drought tolerance via mechanism such as enhanced energy production, enhanced expression of drought stress responsive defense genes, osmoregulation, redox homeostasis, strengthening of the plant cell wall and membrane remodeling.…”