Symbiotic Modulation as a Driver of Niche Expansion of Coastal Plants in the San Juan Archipelago of Washington State

Abstract

Modern evolutionary theory and population genetics posit that adaptation and habitat expansion of plants result from processes exclusive to their genomes. Here, we present studies showing that plants can grow across complex habitat gradients by modulating symbiotic associations with Class 2 fungal endophytes. Endophyte analysis of three native (Leymus mollis, Distichlis spicata, and Salicornia pacifica) and one invasive (Spartina anglica) plant growing across adjacent microhabitats in the San Juan Archipelago altered associations with Class 2 fungal endophytes in response to soil salinity levels. At the microhabitat interfaces where the gradation of salinity varied, the plants were colonized by endophytes from both microhabitats. A reciprocal transplant study along a salt gradient demonstrated that Leymus mollis (dunegrass) required endophytes indigenous to each microhabitat for optimal fitness and/or survival. In contrast, when dunegrass and Grindelia integrifolia (gumweed) were found growing in low salinity, but high drought habitats, these plant species had their own unique dominant endophyte association regardless of geographic proximity and conferred drought but not high salt stress tolerance. Modulation of endophyte abundance occurred in planta based on the ability of the symbiont to confer tolerance to the stress imposed on plants. The ability of an endophyte to confer appropriate stress tolerance resulted in a significant increase of in planta fungal abundance. Conversely, the inability of an endophyte to confer stress tolerance resulted in a decrease of in planta fungal abundance. Our studies indicate that Class 2 fungal endophytes can provide a symbiotic mechanism for niche expansion and phenotypic plasticity across environmental gradients.

Selection of Salinity-Adapted Endorhizal Fungal Consortia from Two Inoculum Sources and Six Halophyte Plants

“…Few reports have reported the composition of the endophytic fungal community of D. spicata . Redman et al [ 101 ] informed that DSF of the genera Phoma sp. and Fusarium sp.…”

Uniting the Role of Endophytic Fungi against Plant Pathogens and Their Interaction

“…Fusarium solani , isolated from tomato plants, was reported to promote ISR against foliar pathogen Septorialyco persici by activating the PR, PR7, and PR5 genes in the root [ 85 ]. In another study, non-pathogenic mutant of Colletotrichum magna strains induced resistance in Citrullus lanatus and Cucumis sativus plants by producing large amounts of peroxidase, phenylalanine ammonia lyase enzyme, and lignin deposition, which helped protect the plants from infection caused by C. orbiculare and F. oxysporum [ 19 , 86 , 87 ]. Furthermore, the contact of Neotyphodium lolii with different pathogens decreased leaf lesions and necrotic spots disease symptoms by enhancing superoxide dismutase and peroxidase activities in the host plant [ 88 ].…”

The microbiome of an amphibious plant shifts dramatically across the host life cycle

“…Symbiosis with microbes can improve plant health and habitat adaptation in natural and artificial environments, with several plant traits co-regulated by the associated microbiome and the plant's genome (Rodriguez, et al 2009;Morelli, et al 2020). Research focusing on symbiotic associations can also enhance ecological theory and may even lead to the development of new biotechnology (Redman et al, 2022). Among symbionts, microbial inhabitants of the rhizosphere and phyllosphere are considered epiphytes, whereas microbes residing within plant tissues (the endosphere) are considered endophytes.…”

“…In addition, existing evidence suggests that variation in the abiotic and biotic environment can also exert direct and indirect effects on plant-associated microbiota; climate-driven geographical variation can drive the composition of a microbiome (Oono, et al 2017;Harrison & Griffin, 2019). The plant microbiome therefore holds interesting parallels to other environmental systems and their microbiomes-for instance, the gut microbiome or the Earth microbiome-with conceptually similar questions regarding horizontal transfer of symbionts, diversity drivers, and influence in host niche expansion and plasticity (Redman et al, 2011;Redman et al, 2022).This is of importance in a global change context, for example, as global temperature increases and variation in both abiotic and biotic factors can indirectly shape plant microbiota through plant responses (Suryanarayanan & Shaanker, 2021;Ware, et al 2021). Given the known importance of plant microbiomes and their variations, examining the communities present on and within different and unique plant species has the potential to provide new insights.…”