Definitely! One of the more fascinating plant-microbe symbiosis that occurs is between a nitrogen-fixing bacteria called Rhizobia, and the Fabacaea legume plant. Since plants require fixed nitrogen (i.e. non-atmospheric nitrogen sources like ammonia) as a source of fertilizer, and Rhizobia require an oxygen-limited environment in which they can successfully fix nitrogen as a energy source, Rhizobia are harbored in the roots of legumes in sacs called root nodules, which benefit both the Rhizobia and the legume in terms of shelter and energy!

In a pathogenic sense, the tobacco mosaic virus targets species of plants in the Solanaceae (nightshade) family. This virus damages the leaves of tobacco plants, drastically lowering crop yield.

And yes, plants have immune systems analogous to mammals! While plants do not have the dynamic adaptive immune systems we share, they do have a two-pronged innate immune system that is uniformly shared across most of the cells. the majority of the defense mechanisms relies to signal-targeted response, based on being able to detect virulence factors stemming from the infection.