He found that the parasitic and the host plants were exchanging thousands of mRNA molecules between each other, thus creating a conversation.
I think this is a little bit of a misuse / misunderstanding of the term / concept "communication".
I think that if you were a cell biologist, you would get the message more clearly. And mRNA is *literally* a message written in a language. As that message is passed around and read, it's translation has effects. This is the basis of communication -- a message, received, having impact.
The more geeked out you get on biology/molecular-biology, the more obvious it becomes that each life form is a set of instructions that yield an explosion of self interested, self-replicating, adaptive and protective technologies -- all so long as the basic needs of the life form are met or available enough.
And so words like 'communication' can end up making perfect sense in a non anthropocentric way. Ultimately, the words make sense in describing biology, and lose their archaic contextual connotations.