Endophytic fungi and climate change

Endophyte hyphae in leaf

Endophytes are a group of fungi that live inside of plants. I study two particular species: Neotyphodium lolii and N. coenophialum. These fungi infect perennial ryegrass and tall fescue respectively. The Neotyphodium species have been refereed to as "trapped parasites". The live asexually entirely within the host plant. They spread only vegetatively via tillering or through the seeds of infected plants. There is no known route of horizontal transmission of the fungus from infected to uninfected grass plants. Because these fungi are trapped within their host, it is thought that the relationship between plant and fungi has evolved away from parasitism and toward mutualism.

We have shown that the presence of the endophyte moderates the plants' responses to elevated CO2. One common plant response to elevated CO2 is a reduction in plant protein. We have shown in both grass species that this reduction is not as great in plants infected with the endophyte than for endophyte-free plants. Another common response of grasses to elevated CO2 is an increase in plant carbohydrate (CHO). Again, we have shown that the presence of the endophyte moderates this repsonse. Endophyte-infected individuals show less accumulation of CHO than endophyte-free plants. In addition to CHO and protein, another common response is a reduction in chlorophyll content under high CO2. We have found that this reduction is much less in endophyte-infected plants.

We have also shown that endophyte-infected plants photosynthesize more than endophyte-free plant, particularly under conditions of high soil N. Together, these results suggest that the endophyte is manipulating the plant's N-metabolism, perhaps through its production of Rubisco. This hypothesis ramains to be test.

We have recently started new work in this area testing how changes in CO2 concentrations might change the abundance of the endophytic fungi within the plant.

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