These results indicated that knocking out ATHB8 and ATHB15/CNA genes does not affect syncytium formation and syncytium expansion in the Arabidopsis root, probably due to high redundancy of HD-ZIP III family genes in mediating vascular cell differentiation, and that all five members were up-regulated at the BCN infection site [67,87](S8 Fig). Here, PPP3CA is linked to infection.