Jayawardhane, K.; Somarathna, T.; Manoli, V. P.; Hwang, S.-F.; Strelkov, S. E.; Singer, S. D.; Chen, G. G.

Soilborne pathogens can be highly devastating, and clubroot, caused by Plasmodiophora brassicae, is particularly destructive to cruciferous plants. Although many AP2/ERF family transcription factors (TFs) have crucial physiological functions, very little is known regarding their functions in the context of soilborne diseases. Here we investigated the roles of AINTEGUMENTA-LIKE 7 (AIL7), an AIL sub-family TF in the AP2/ERF family, in plant immunity against clubroot. Unexpectedly, both AIL7 overexpression and mutant Arabidopsis lines exhibited increased tolerance to P. brassicae. Subsequent analysis revealed significant transcriptional alterations in genes linked to pathogen response, along with notable differences in genes associated with salicylic acid (SA) and jasmonic acid (JA) defense pathways, compared to wild-type plants. Interestingly, there was a tendency for up-regulation of SA- and JA-related genes in AIL7 overexpression and mutant lines in the absence, rather than presence, of P. brassicae. Subsequent phytohormone analyses confirmed these results. Taken together, AIL7 has an important role in maintaining constitutive systemic acquired resistance, involving phytohormone mediated defense, and this, rather than an accumulation of SA following P. brassicae challenge, primes the plants for improved clubroot resistance, which would shed light on exploring the functions of other AP2/ERF family TFs in plant immunity against soilborne pathogens.