Elucidating putative novel functions of the AINTEGUMENTA-LIKE 7 transcription factor in clubroot resistance in Arabidopsis.

Clubroot caused by Plasmodiophora brassicae is a devastating soilborne disease of the Brassicaceae worldwide. Disease management often relies on disease resistant cultivars, but their overuse has led to the break down of resistance. As such, it is important to elucidate novel gene targets for clubroot tolerance. AINTEGUMENTA-LIKE 7 (AIL7), a transcription factor in the AP2/ERF family, has been observed to influence the expression of genes involved in biotic stress response when overexpressed in Arabidopsis seeds in our previous study. Here we evaluated the resistance of Arabidopsis lines that constitutively overexpressed AIL7, as well as an ail7 T-DNA mutant, to P. brassicae, and found that both mutant and overexpression lines displayed reduced clubroot symptoms and pathogen spore load in infected tissues. Targeted gene expression analysis revealed significant alterations in the transcript levels of genes linked to pathogen response, along with notable differences in those associated with salicylic acid (SA) and jasmonic acid (JA) defense pathways. Interestingly, the SA- and JA-related genes had a tendency for up-regulation in AIL7 overexpression and mutant lines in the absence, rather than presence, of P. brassicae, and phytohormone analyses confirmed these results. These findings indicate that phytohormone-mediated defense pathways are constitutively activated in Arabidopsis lines in which AIL7 is either overexpressed or knocked out, which likely contributes to a reduction in disease symptoms. Taken together, these findings suggest that AIL7 could be a potential target for improving plant responses to clubroot. However, more extensive evaluation across a broader range of inoculum levels and pathotypes will be necessary to assess its relevance for breeding resistant cultivars.