Endophytic Streptomyces population induced by L-glutamic acid enhances plant resilience to abiotic stresses in tomato

Abstract

Endophyte bacteria, which colonize plants including roots, stem, flower, and fruit, it can derive their nutrients from the host, are recognized for their mutualistic relationship with the host plant. They play a critical role in promoting host growth and modulating abiotic stress. Carbon and nitrogen have a significant impact on bacterial population and secondary metabolite production, which are highly specific in various categories such as bacterial growth regulation, anti-compounds production. Application of L-glutamic acid can significantly enhance Streptomyces globisporus population buildup in plants. However, the effectiveness of this population buildup against abiotic stresses such as salinity and drought has not been investigated. Therefore, in this study, we tested the bacteria and their prebiotic activity against salinity and drought stress in tomato plants. Three different amino acids were treated on the tomato plants, and it was observed that L-asparagine and L-proline had a negative effect on plant growth and phenotype, while L-glutamic acid promoted plant growth and increased bacteria population density. The bacteria were found to colonize the rhizosphere and root endosphere, with colonization being promoted by L-glutamic acid. Additionally, Streptomyces was found to have plant growth promotion effects and provided protection against abiotic stresses. Interestingly, L-glutamic acid reduced the damage caused by salinity stress, but not drought stress. These findings suggest that L-glutamic acid plays a role in providing tolerance to salinity stress with the core microbiota, thus the current study demonstrated their prebiotic activity in the agriculture system.

Antifungal Properties of Streptomyces bacillaris S8 for Biological Control Applications

“…Streptomyces strains have been recognized for their ability to produce diverse secondary metabolites with significant roles in plant defense against pathogens ( Bentley et al, 2002 ; Deshpande et al, 1988 ; Lee et al, 2020 ). Apart from their well-established role in suppressing plant diseases, Streptomyces is increasingly gaining attention as a potential abiotic stress controller through the production of various secondary metabolites ( Durán et al, 2018 ; Harir et al, 2018 ; Yagüe et al, 2012 ) The importance on biological control approaches in sustainable agriculture, particularly involving the Streptomyces genus have been underscored ( Cha et al, 2016 ; Genilloud, 2017 ; Kim and Kwak, 2023 ; Kim et al, 2019 ; Oskay, 2009 ). Given the broad spectrum of Streptomyces interactions with host plants, these bacteria emerge as an excellent model system for studying plant-microbe interactions ( Lindow and Brandl, 2003 ; Redford et al, 2010 ).…”

“…The genome of S. bacillaris S8 was previously characterized by Kim and Kwak (2023) , underscoring its importance in the synthesis of antifungal metabolites effective against large patch disease ( Jeon et al, 2021 ). To identify potential secondary metabolite gene clusters within this strain, we utilized the antiSMASH 7.0 version tool ( https://docs.antismash.secondarymetabolites.org ) ( Blin et al, 2023 ).…”

“…Streptomyces bacillaris S8 has previously been acknowledged for its potent biocontrol capabilities against large patch disease in turfgrass, with the identification of the valinomycin biosynthetic gene cluster ( Jeon et al, 2019 ). Building upon this, our investigation aimed to explore its potential as a biocontrol agent in soybeans, motivated by its relevance to plant health ( Kim and Kwak, 2023 ). The identified gene clusters within the bacteria were found to include genes associated with the production of nonribosomal peptide synthetase (NRPS) or polyketide synthase (PKS) compounds, as detailed in Table 1 .…”