The Mushroom Overminds
Everywhere there are mushrooms a gigantic network grows underground, made out of mycelium. The mushrooms can connect to this network and communicate with each other via a combination of hormones, proteins, and electrical signals, pretty similar to the Internet of humans, but a lot cooler. The networks themselves are semi-sentient beings, sometimes referred to as "overminds". There are several notable properties of these overminds that make them unique throughout the galaxy.
The overminds can store information. in fact, they can store a mushroom's entire consciousness. What this means is that if a mushroom is dying, it needs only to connect to the overmind underground network and let its body wither away. A new body can then regrow anywhere on the network and get imbued with the consciousness of the mushroom. This makes them pretty much immortal by aging, allowing them to live for eons, by constantly regenerating.
Being a giant electrical network the overminds act as antennas. It is not clear how exactly they do it, but they can communicate with each other at speed defying the known laws of physics, allowing for instant transfer of information over pretty much unlimited distances. This, combined with the previous property allows mushrooms to travel from planet to planet, by letting their bodies die and regrowing at the destination. It is a form of teleportation, although it takes some time for the new body to grow.
After the human-mushroom wars were over and the period of peace and good relationships began, humans found a way to use those overminds to increase the power of their own internet systems, allowing them instant communication with any other human colony. As a result of that, every human seedship that colonized new planets has on board a vial of mushroom spored, from which a new mycelial network can grow and a new overmind can develop.
