C4A and infection: We found that the expression level of ATHB12 was correlated with the severity of abnormal development in C4 transgenic plants and that infection of Arabidopsis with a BCTV c4 mutant did not induce significant symptom development or ATHB12 gene expression, implying a relationship between the functions of the BSCTV C4 protein and the effects of ATHB12 induction on symptom development.