Extending permisso di soggiorno

HI
I am a PhD student in Messina sicilia and my permisso di Soggiorno will expire in july. can I extend my Permesso di Soggiorno for a year? What would I need to do to make this possible?

It is possible, but under very strict guidelines.  Your best course of action would be to contact the Questura and get the definitive answer regarding that.  As far as I know, as long as you can prove you are in good standing with the university, are enrolled in further studies, and all of the other requirements that are required to get the permesso in the first place, you should be successful, but there are never any guarantees.