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cAMP signalling regulates synchronised growth of symbiotic Epichloë fungi with the host grass Lolium perenne

journal contribution
posted on 2023-05-03, 16:44 authored by Christine VoiseyChristine Voisey, Michael Christensen, Linda JohnsonLinda Johnson, Natasha Forester, Milan Gagic, Gregory Bryan, Wayne SimpsonWayne Simpson, Damien Fleetwood, Stuart CardStuart Card, John Koolaard, Paul MacleanPaul Maclean, Richard JohnsonRichard Johnson
The seed-transmitted fungal symbiont, Epichloë festucae colonises grasses by infecting host tissues as they form on the shoot apical meristem (SAM) of the seedling. How this fungus accommodates the complexities of plant developmental to successfully colonise the leaves and inflorescences is unclear. Since adenosine 3′,5′-cyclic monophosphate (cAMP)-dependent signalling is often essential for host colonisation by fungal pathogens, we disrupted the cAMP cascade by insertional mutagenesis of the E. festucae adenylate cyclase gene (acyA). Consistent other fungi, disruption mutants had a slow radial growth rate in culture and hyphae were convoluted and hyper-branched suggesting that fungal apical dominance had been disrupted. Nitro blue tetrazolium staining of hyphae showed that cAMP disruption mutants were impaired in their ability to synthesise superoxide, indicating that cAMP signalling regulates accumulation of ROS. Despite significant defects in hyphal growth and ROS production E. festucae ΔacyA mutants were infectious and capable of forming symbiotic associations with grasses, albeit at a lesser infection frequency than wild-type. Plants infected with E. festucae ΔacyA were indistinguishable from controls, however microscopic evidence showed that hyphae were hyper-branched, and leaf tissues heavily colonised, indicating that the tight regulation of hyphal growth normally observed in maturing leaves requires a functional cAMP signalling cascade.


Rights statement

Copyright © 2016 Voisey, Christensen, Johnson, Forester, Gagic, Bryan, Simpson, Fleetwood, Card, Koolaard, Maclean and Johnson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.


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Frontiers Media




Voisey, C. R., Christensen, M. T., Johnson, L. J., Forester, N. T., Gagic, M., Bryan, G. T., … Johnson, R. D. (2016). cAMP signalling regulates synchronised growth of symbiotic Epichloë fungi with the host grass Lolium perenne, 7, 1546. doi:10.3389/fpls.2016.01546

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