Ungulate saliva inhibits a grass-endophyte mutualism

Area of Science:

• Plant-microbe interactions
• Chemical ecology
• Ecology and evolution

Background:

• Fungal endophytes enhance plant defenses against herbivores via toxic alkaloids.
• The impact of herbivore saliva on fungal endophytes remains understudied.
• Herbivore saliva may possess mechanisms to counteract plant-endophyte mutualisms.

Purpose of the Study:

• To investigate the effect of moose and reindeer saliva on the foliar endophyte Epichloë festucae.
• To determine if herbivore saliva can inhibit endophyte growth and alkaloid production in Festuca rubra.

Main Methods:

• In vitro testing of moose and reindeer saliva on isolated Epichloë festucae hyphal elongation.
• Assessing ergovaline alkaloid levels in Festuca rubra plants treated with moose saliva after simulated grazing.
• Comparing endophyte responses in Festuca rubra genotypes from different distribution limits.

Main Results:

• Both moose and reindeer saliva significantly reduced endophyte hyphal growth compared to water.
• Moose saliva inhibited the induction of ergovaline in Festuca rubra from the core distribution.
• Ergovaline was constitutively expressed in genotypes from the southern distribution limit, irrespective of saliva treatment.

Conclusions:

• Ungulate saliva can actively counteract plant defenses mediated by grass-endophyte mutualisms.
• This study provides the first evidence of herbivore saliva impacting fungal endophyte-plant interactions.
• Herbivore saliva represents a novel factor influencing the dynamics of plant-endophyte-herbivore relationships.