Complex sentence: Phytoplasmas contain a major antigenic protein that makes up the majority of their cell surface proteins and this has been shown to interact with insect microfilament complexes and is believed to the determining factor is insect-phytoplasma interation.
Split into simpler sentences: Phytoplasmas contain a major antigenic protein that makes up the majority of their cell surface proteins. This protein has been shown to interact with insect microfilament complexes and is believed to the determining factor is insect-phytoplasma interation.