Plant Growth Promotion and Stress Tolerance Enhancement through Inoculation with Bacillus proteolyticus OSUB18

Abstract

The isolation of B. proteolyticus OSUB18 from switchgrass unveiled its significant potential in both the enhancement of plant growth and the suppression of plant diseases in our previous study. The elucidation of the related mechanisms governing this intricate plant–microbe interaction involved the utilization of the model plant Arabidopsis thaliana. In our comprehensive study on Arabidopsis, OSUB18 treatment was found to significantly alter root architecture and enhance plant growth under various abiotic stresses. An RNA-seq analysis revealed that OSUB18 modified gene expression, notably upregulating the genes involved in glucosinolate biosynthesis and plant defense, while downregulating those related to flavonoid biosynthesis and wound response. Importantly, OSUB18 also induces systemic resistance in Arabidopsis against a spectrum of bacterial and fungal pathogens and exhibits antagonistic effects on phytopathogenic bacteria, fungi, and oomycetes, highlighting its potential as a beneficial agent in plant stress management and pathogen resistance. Overall, our findings substantiate that OSUB18 exerts a stimulatory influence on plant growth and health, potentially attributed to the remodeling of root architecture, defense signaling, and the comprehensive mitigation of various biotic and abiotic stresses.

Plant Growth Promotion and Plant Disease Suppression Induced by Bacillus amyloliquefaciens Strain GD4a

“…In addition to their direct impact on inhibiting pathogens, beneficial bacteria also indirectly manage plant pathogens by modulating host plant immunity through mechanisms like ISR and SAR [ 46 , 47 , 57 , 58 ]. ISR and SAR are two different types of systemic plant defense mechanisms.…”

“…Tomato cultivars M82 and Micro-Tom as well as strawberry cultivar Monterey-UC were employed in our research. These plants were cultivated in a greenhouse with conditions set at 22 °C temperature, 16 h light cycles, and roughly 45% relative humidity, following previously established protocols [ 33 , 47 ].…”

“…We used D747 as a positive control for this study. Phytopathogenic fungi including Botrytis cinerea , Fusarium oxysorum , Fusarium graminearum , and Magnaporthe oryzae , as well as oomycetes such as Phytophthora capsici and Pythium irregulare , were all cultivated on Potato Dextrose Agar (PDA) at a temperature of 25 °C [ 46 , 47 ].…”

“…The plant growth promotion assay was conducted following the procedure outlined in the previous study [47], with slight adaptations. In summary, sterile Arabidopsis Col-0 seeds were placed onto a 10 cm petri dish containing 25 mL of agar-solidified 0.5× Murashige and Skoog (MS) medium, following a 3-day vernalization at 4 • C. Small 10 µL drops of a bacterial suspension with an OD600 = 0.1 were applied at a distance of 5 cm from the seeds.…”

“…Bioactive secondary metabolites produced by B. mojavensis have promising applications in the agricultural, food, and clinical fields [ 40 , 41 , 42 , 43 , 44 , 45 ]. Additionally, Bacillus proteolyticus OSUB18 has been shown to activate the induced systemic resistance (ISR) against gray mold fungus in Arabidopsis while also directly impeding fungal growth [ 46 , 47 ]. On another front, Pst DC3000, a pathovar of Pseudomonas syringae , is recognized for causing bacterial speck disease in tomato and Arabidopsis plants [ 48 , 49 , 50 , 51 ].…”