Searching for a Subtle Seed-borne Systemic Symbiosis

Published by Cori VanGalder on

Searching for a Subtle Seed-borne Systemic Symbiosis

Submitted by: Christopher Schardl

In 1985 I came to Lexington, Kentucky, to take a junior faculty position in the Department of Plant Pathology at the University of Kentucky (UK). I was soon to be followed by my wife, Kuey, eight-months pregnant. (She put off ending her productive postdoc at the MRC in Cambridge, England, until the last possible day, and who could blame her?!). Then we had a newborn daughter (Anisa), and a week later, bought and moved into a new house. So, this piece is about the house…sort of…since that’s where Kuey and I are spending more time together than we perhaps have ever done in all that time.

Given our frantic life altering activities in 1985, it would be an exaggeration to claim that we were deeply thoughtful when choosing our new home. But it has turned out well, and we are still there. Here are the advantages: Location, location, location.

Location: We live immediately south of campus. It was a 10-minute walk to work when I started, and in 2003 they built a new building much closer and moved me into it, so that now it’s a mere 10-minute walk. (I’m older now.)

Location: The neighborhood has been rezoned as H1-historic.

Location: It is a 10-minute walk to the Arboretum (managed by UK).

Now a digression to…I dunno…mycology?

In 1985 I moved to UK with no experience in mycology. None! During my interview they asked me what I wanted to work on, and I said fungi. That was a crazy answer! I’m not sure they even believed me. But a conversation during my interview did help push me in that direction: with Malcolm Siegel, who described the “tall fescue endophyte.”

Even so, it took me a little while to settle on that. Instead I started collaborating with David A. Smith on something called Fusarium solani. But the Dean bribed me (with postdoctoral seed money) to start working on the endophyte, which we now know as Epichloë coenophiala.

Back then (for those young folks among you), many fungi eschewed Linnaeus and had separate teleomorphs and anamorphs. So, even though “Epichloë” is a venerable old teleomorph name we couldn’t apply it to the tall fescue endophyte because it is asexual. (In fact, we now know E. coenophiala is triploid and can’t do meiosis to save its life!) Even so, there were a lot of similarities between “the endophyte” and “grass choke pathogens,” the legitimate teleomorphic Epichloë species. Just to nail that down, my lab became PCR fanatics—as soon as we could buy three heated waterbaths, three thermometers, and some Taq polymerase—and DNA sequencing fanatics. And we nailed that down in a 1991 paper.

Now we just send DNA and RNA “out” to be sequenced so that we can work wherever (except “at work”) on the sequence data, using a laptop as a terminal. But we can also don masks to hide our identities, sneak out to the Lexington Arboretum, and find the “real” Epichloë, which is objectively as beautiful as any fungus.

Three-way symbiosis. The golden structures resembling tiny Typha heads (cattails) are fruiting structures of Epichloë elymi. The fungus is a systemic symbiont of Elymus spp. grasses (this one is Elymus villosus), and the structure visible near the base of the top one is the larval case of the third symbiont, a fly of genus Botanophila (species undescribed). The fly larva emerges at night and eats developing perithecia, resulting in the feeding tracks. The fungus is heterothallic and is ‘pollinated’ by the mother Botanophila fly. Another twist to this system is that E. elymi can also transmit vertically (and clonally) as a heritable symbiont of the grass. The photo was taken in The Arboretum State Botanical Garden of Kentucky on 26 May 2020.
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