Drooling over plants changes their chemistry

New research from the Tanentzap group that has been published in the journal Biology Letters and is featured by Science Magazine and in the 23 July issue of New Scientist.

Plants host a remarkable diversity of symbiotic fungi.  Some of these, such as those associated with grasses, produce secondary metabolites that are intended to deter herbivores.  This latest research shows that herbivores can directly combat this mutualistic interaction through compounds in their saliva.  Experiments with endophytic fungi isolated from red fescue found that colonies grew more slowly within 36 hours after being treated with moose and reindeer saliva but not water.  In whole plants, saliva also seemed to deactivate defense signalling pathways.  Plants from populations with inducible defenses produced about 100% more of the toxic alkaloid ergovaline when experimentally clipped but nearly 70% less when saliva accompanied the simulated grazing.  This now overturns the perception that animals simply avoid or detoxify toxins, and suggests they can actively combat plant defenses.