ARF5 and infection: The auxin type 1-NAA was much more effective than trans-zeatin in activating the Ipt promoter, but again, not for the promoters of IaaH or IaaM. Elevated levels of free IAA are detectable in infected tissues six days after inoculation with A. tumefaciens strain C58 [20] and at the same infection stage, expression of the ARF5 gene begins to increase, as shown in the microarray data (1.49 fold, P value = 0.006) [20,46].