Plasma membrane virulence factor required for spreading and inducing tumors in infected leaves. Expression is highly up-regulated during all stages of pathogenic development (PubMed:21692877). Expression is positively regulated by the unfolded protein response (UPR) signaling via the binding of CIB1 to the UPRE motif localized at the PIT1/PIT2 promoter (PubMed:27093436). O-mannosylated by PMT4 (PubMed:22416226). Is also N-glycosylated (PubMed:22416226). Keeps the ability to penetrate maize epidermis and to grow intracellularly at sites of infection but fails to spread and induce tumors in infected leaves.