Plants possess seed-transmitted host-adapted endophytic microbes that play roles in modulation of plant development, improvement of oxidative stress resistance, and acquisition of nutrients to support plant growth. Invasive plants (e.g., Phragmites australis) support a suite of microbes that have been implicated in their invasive characteristics. However, it is not clear how stable the symbiotic relationships are in the presence of microbes not normally found in the plant. Therefore, we hypothesized that introduction of endophytic microbes from other hosts into a plant may displace endophytes already there and disrupt functions of the endophyte-host symbiosis. We apply the term ‘endobiome interference’ to denominate the condition where entry of introduced microbial endophytes into plant cells and tissues results in displacement of existing endophytic microbes and disruption of functions of the plant-supported endophyte-host symbiosis. We examined seedlings of several species microscopically using reactive oxygen stain to visualize microbes within tissues. Microbes were isolated, identified using rDNA sequence data, and inoculated onto seedlings of test species to evaluate effects. Test seedlings were again stained with reactive oxygen stain and examined microscopically to determine distribution of microbes. In this research, we report two instances of ‘endobiome interference’ involving fungal and bacterial endophytes.
Results/Conclusions
We found that a fungal endophyte (Aureobasidium pullulans), isolated from seedling roots of a weedy but native plant species Froelichia gracilis (Hook.) Moq. (snakecotton), entered into cells and tissues of seedling roots of the non-native plant species Amaranthus hypochondriacus L. (Prince-of-Wales feather). Once inside the cells, the fungus excluded the plant’s existing endophytic microbes and repressed growth of seedling roots and shoots. Similarly, a bacterial endophyte (Micrococcus luteus) originally isolated from tomato seedlings was capable of entry into seedling root cells of multiple introduced species (including Phragmites australis (Cav.) Trin. Ex Steud, Poa annua L., Fallopia japonica Siebold & Zucc., Rumex crispus L., and Taraxacum officinale F.H. Wigg.), resulting in displacement of existing endophytic bacteria and suppression of seedling growth. We hypothesize that ‘endobiome interference’ may be a common occurrence in natural plant communities and could be one tool that plants employ to limit growth of competitor plant species. We are currently exploring the application of ‘endobiome interference’ as a way to reduce the invasive character of invasive and weedy plant species and develop novel control strategies for non-native P. australis, a priority for the Great Lakes Phragmites Collaborative (http://www.greatlakesphragmites.net/) and managers nationwide.