Iron-Grabber Important for Endophyte Survival

Iron-Grabber Important for Endophyte Survival

Scientists at New Zealand’s largest Crown Research Institute, AgResearch, have made a crucial discovery on what makes endophytes succeed in ryegrass.

In a paper recently published in the prestigious journal PLOS Pathogens, lead author Dr Linda Johnson describes the tactic used by an endophyte to extract a vital nutrient, iron, from its ryegrass host.

Paddocks of flourishing ryegrass are a typical New Zealand scene. Hidden within the grass, however, lies an invisible helper: an endophytic fungus that protects pastures from being decimated by unwanted pests, ultimately increasing pasture production and persistence.

The endophyte produces a small molecule, known as a siderophore, which grabs and binds strongly to iron, an element essential to both the host and fungal partner. This iron-grabbing trick is widespread among fungi, with common human fungal infections such as thrush and athlete’s foot depending on the iron they quietly filch from us. However, it is the fascinating result of experimentally deleting the iron-grabbing siderophore gene from an endophytic fungus that led to its publication in PLOS* Pathogens.

“Eliminating the siderophore caused major problems for both the fungal endophyte and the host grass plant,” explains lead author Dr Linda Johnson, AgResearch science team leader for Plant-Fungal Interactions. “The usual tightly controlled, synchronous growth of the fungus inside the ryegrass became deformed and unregulated. The host plants were stunted, and in extreme cases both the fungus and host plant died.”

This is the first report that siderophores are essential to the mutually beneficial relationship between ryegrass and endophyte. The relationship is crucial for New Zealand agriculture. The research is part of a large AgResearch programme to find better endophytes for our main pasture plant that produce bioactive compounds that protect pasture from insect attack and are also animal-safe.

Although ryegrass can exist without an endophyte, in New Zealand it is rapidly decimated by insects such as the Argentine stem weevil and black beetle.

AgResearch is the world’s major centre for endophyte research, and was the first to discover stock-friendly, anti-insect endophytes that are now commercially available and widely used nationally and internationally. They continue to search for even better ‘designer’ endophytes.

“We don’t yet have the best possible endophyte in terms of pest protection, animal safety and host compatibility,” says Dr Johnson. “We actively look for new endophytes from around the world, but to identify better performers that can live in pasture grasses we need to know more about the fungal-host interaction. To do that well, this fundamental research into how grasses and endophytes interact is essential.”

ENDS

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