C3 and infection: To further precisely delineate this critical region, a series of C3 truncated mutants expressed by the pCV vector, including C3(1–87) (reserved the amino acid region from residues 1 to 87 of C3), C3(1–94), C3(1–101), C3(1–108), C3(1–115), C3(1–122) and C3(1–129), were constructed and subjected to local infection assays accompanied by TbCSVdC3 in N. benthamiana, as described earlier.