Characterization of Rhodopseudomonas palustris population dynamics on tobacco phyllosphere and induction of plant resistance to Tobacco mosaic virus

Abstract

Summary Although many biocontrol bacteria can be used to improve plant tolerance to stresses and to promote plant growth, the hostile environmental conditions on plant phyllosphere and the limited knowledge on bacterial colonization on plant phyllosphere minimized the beneficial effects produced by the biocontrol bacteria. Rhodopseudomonas palustris strain GJ‐22 is known as a phyllosphere biocontrol agent. In this paper, we described detailed processes of strain GJ‐22 colony establishment at various colonization stages. Four different types of bacterial colonies, Type 1, scattered single cells; Type 2, small cell clusters; Type 3, small cell aggregates; and Type 4, large cell aggregates, were observed in the course of bacterial colonization. We categorized bacterial colonization into four phases, which were, Phase I: bacterial colony exists as Type 1 and cell population reduced quickly; Phase II: Type 1 evolved into Type 2 and cell population remained steady; Phase III: Type 3 arose and replaced Type 2, and cell population expanded slowly; and Phase IV: Type 3 matured into Type 4 and cell population increased quickly. We have shown that the preferable location sites of bacterial aggregates on leaf phyllosphere are grooves between plant epidermal cells. Analyses of expressions of plant defence‐related genes showed that, starting from Phase III, bacterial cells in the Type 3 and Type 4 colonies produced unidentified signals to induce host defence against Tobacco mosaic virus infection. In addition, we determined the crucial role of aggregates formation of GJ‐22 cell on plant phyllosphere in terms of bacterial cell stress tolerance and ISR (induced systemic resistance) priming. To our knowledge, this is the first report focused on the colonization process of a phyllosphere biocontrol agent and gave a clear description on the morphological shift of bacterial colony on phyllosphere.

Diversity and potential biogeochemical impacts of viruses in bulk and rhizosphere soils

“…Recently, Shen and his team successfully used phage treatment to decrease the incidence of disease of tomato (Wang et al ., 2019), but the use of phage biocontrol is still poorly studied. Many microbes have been reported as biocontrol agents, for example, Pseudomonas isolated from maize rhizospheres and Rhodopseudomonas palustris colonizing tobacco phyllosphere (Costa et al ., 2006; Su et al ., 2019).…”

From Lab to Farm: Elucidating the Beneficial Roles of Photosynthetic Bacteria in Sustainable Agriculture

“…Studies have indicated that PNSB play a role in plant disease control by mitigating biotic stresses. Su and colleagues reported that preinoculation of R. palustris GJ-22 (isolated from activated sludge) on tobacco could elevate plant immunity during subsequent tobacco mosaic virus (TMV) infection and reduce the infection rate of TMV on leaves [73][74][75]. R. palustris KTSSR54 (isolated from Kan-Tulee peat swamp forest, Thachana district, Surat-Thani Province, Thailand) was shown to protect rice from infection by fungal pathogens, particularly those cultivated in acidic soils [76,77].…”

“…PGPR-elicited ISR enhances the defensive capacity of host plants and reduces damage from pathogens [140]. Su and colleagues reported that inoculating R. palustris GJ-22 onto tobacco (Nicotiana benthamiana) leaves could induce ISR to TMV [73,74]. The abundance of TMV was reduced to a remarkable extent, the activities of defensive enzymes were enhanced and the transcripts of pathogenesis-related (PR) genes were upregulated [73,74].…”

The Photosynthetic Bacterium Rhodopseudomonas palustris Strain PS3 Exerts Plant Growth-Promoting Effects by Stimulating Nitrogen Uptake and Elevating Auxin Levels in Expanding Leaves

“… Ge and Zhang (2019) reported that Rhodopseudomonas palustris G5 could exert beneficial effects on cucumber seedling growth and salt tolerance via indole-3-acetic acid (IAA) and 5-aminolevulinic acid (ALA) production. In addition, a R. palustris strain, GJ-22, was investigated for its biocontrol ability of triggering induced systemic resistance (ISR) against tobacco mosaic virus (TMV) in tobacco plants, and this paper also identified the crucial aggregation stage of GJ-22 strain colonization in the initiation of ISR priming in the plant ( Su et al, 2019 ). In our previous study, two IAA-producing strains of R. palustris (PS3 and YSC3) were isolated from paddy fields in Taiwan and PS3 strain exerted plant-growth promoting effects in enhancing shoot fresh weight and the plant nitrogen use efficiency (NUE) of Chinese cabbage in soil pot system ( Wong et al, 2014 ).…”