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Paenibacillus taichungensis strain E222: Mother and progeny plant growth promotion and association with an Epichloë fungal endophyte

Year: 2025

Type: article

Abstract: There are limited publications evaluating the effects of bacteria on plant-fungal symbioses. We evaluated the effects of a bacterium (designated strain E222) on perennial ryegrass (Lolium perenne) symbiotically associated with an Epichloë endophyte. Within this tripartite symbiosis, E222 was characterised as an ectosymbiont of Epichloë sp. AR135, the latter a mutualistic endophytic fungus of L. perenne. We hypothesised that (i) E222 would promote host plant growth and not interfere with the in planta production of AR135-derived antiherbivore alkaloids and AR135 growth and (ii) the Epichloë hyphal colonisation of plant seeds would facilitate the E222 entry into the progeny seeds. Via whole genome analysis, E222 was identified as Paenibacillus taichungensis and predicted to possess plant growth-promoting traits. E222 was inoculated on seeds of perennial ryegrass associated with AR135 and the bacterium was systemically present in the subsequent seedlings. E222 promoted the growth of AR135-associated plants, as expected, but reduced AR135-derived alkaloid concentrations and decreased the AR135 biomass at an early plant stage. AR135, but not E222, was detected in the progeny seeds and in line with the absence of E222, growth of progeny seedlings was not affected by the bacterial inoculation of mother plants. The bacterial effects on plants and Epichloë may be explained by the predicted abilities of E222 to promote plant growth (e.g., auxin production) and compete with AR135 for alkaloid precursors (e.g., tryptophan).

Source: Plant Physiology and Biochemistry

DOI: 10.1016/j.plaphy.2025.110851