Paenibacillus lentimorbus Inoculation Enhances Tobacco Growth and Extenuates the Virulence of Cucumber mosaic virus

Abstract

Previous studies with Paenibacillus lentimorbus B-30488” (hereafter referred as B-30488), a plant growth promoting rhizobacteria (PGPR) isolated from cow’s milk, revealed its capabilities to improve plant quality under normal and stress conditions. Present study investigates its potential as a biocontrol agent against an economically important virus, Cucumber mosaic virus (CMV), in Nicotiana tabacum cv. White Burley plants and delineates the physical, biophysical, biochemical and molecular perturbations due to the trilateral interactions of PGPR-host-CMV. Soil inoculation of B-30488 enhanced the plant vigor while significantly decreased the virulence and virus RNA accumulation by ~12 fold (91%) in systemic leaves of CMV infected tobacco plants as compared to the control ones. Histology of these leaves revealed the improved tissue’s health and least aging signs in B-30488 inoculated tobacco plants, with or without CMV infection, and showed lesser intercellular spaces between collenchyma cells, reduced amount of xyloglucans and pectins in connecting primary cells, and higher polyphenol accumulation in hypodermis layer extending to collenchyma cells. B-30488 inoculation has favorably maneuvered the essential biophysical (ion leakage and photosynthetic efficiency) and biochemical (sugar, proline, chlorophyll, malondialdehyde, acid phosphatase and alkaline phosphatase) attributes of tobacco plants to positively regulate and release the virus stress. Moreover, activities of defense related enzymes (ascorbate peroxidase, guaiacol peroxidase, superoxide dismutase and catalase) induced due to CMV-infection were ameliorated with inoculation of B-30488, suggesting systemic induced resistance mediated protection against CMV in tobacco. The quantitative RT-PCR analyses of the genes related to normal plant development, stress and pathogenesis also corroborate well with the biochemical data and revealed the regulation (either up or down) of these genes in favor of plant to combat the CMV mediated stress. These improvements led tobacco plant to produce more flowers and seeds with no negative impact on plant health. The present study may advocate the applicability of B-30488 for crop yield improvement in virus infested areas.

Bacillus atrophaeus HAB-5 secretion metabolites preventing occurrence of systemic diseases in tobacco plant

“…Values were presented as means ± SD from three independent replicates requirements (Elsayed et al 2013). The need for proline in maintaining the elevated ROS level has been reported earlier (Apostol and Heinstein 1989;Kumar et al 2016). Interestingly, our results showed lower proline and ROS accumulation in pretreated plants.…”

Current knowledge and perspectives of Paenibacillus: a review

“…Rather than immediately activating a defensive state, ISR primes for faster and stronger defenses by hypersensitizing the plant to potential threats [64]. A variety of Paenibacillus species seem to elicit ISR against pathogenic bacteria [49, 65], fungi [50, 66–68], nematodes [69], and viruses [70]. …”

“…Similarly, Arabidopsis thaliana is primed by P. alvei K165 against a hemibiotrophic fungus [54], Verticillium dahlia , by both salicylate and jasmonate-dependent pathways [68]; while cucumber is primed by P. elgii MM-B22 against the hemibiotrohic fungus [54] Colletotrichum orbiculare , responding to attack with defense-related enzymes and H 2 O 2 -induced cell death [67]. Priming of tobacco by P. lentimorbus B-30488 also results in accumulation of defense-related enzymes in response to cucumber mosaic virus infection [70]. …”

Mechanisms of Plant Tolerance to RNA Viruses Induced by Plant-Growth-Promoting Microorganisms

“…Thus, it should be noted that the treatment of plants with benzothiadiazole, which is used as a reference in many studies of plant resistance to viruses, despite a decrease in the incidence of viral particles in plants, in some cases, suppressed growth and reduced the weight of plants during viral infection compared with bacterial cultures [54,55]. As it was shown by Kumar and co-workers [49], soil application of Paenibacillus lentimorbus B-30488 enhanced the resistance of tobacco plants to CMV while it maintained photosynthetic activity and plant growth. At the same time, the activity of antioxidant enzymes decreased, expression of genes encoding pathogen-induced proteins increased, and polyphenols accumulated, which subsequently prevented the virus spread through plant tissues [49].…”