Expression and Role of Response Regulating, Biosynthetic and Degrading Genes for Cytokinin Signaling during Clubroot Disease Development.

The obligate biotroph causes clubroot disease in oilseeds and vegetables of the Brassicaceae family, and cytokinins play a vital role in clubroot formation. In this study, we examined the expression patterns of 17 cytokinin-related genes involved in the biosynthesis, signaling, and degradation in Chinese cabbage inoculated with the Korean pathotype group 4 isolate of , Seosan. This isolate produced the most severe clubroot symptoms in Chinese cabbage cultivar "Bullam-3-ho" compared to three other Korean geographical isolates investigated. , a cytokinin biosynthesis gene, was induced on Day 1 and Day 28 in infected root tissues and the upregulation of this biosynthetic gene coincided with the higher expression of the response regulators , on both Days and on Day 1 and 3. and genes were also induced during gall enlargement on Day 35 in leaf tissues. The gene, which positively interact with phytochrome B, was consistently induced in leaf tissues on Day 1, 3, and 14 in the inoculated plants. The cytokinin degrading gene were induced on Day 14, before gall initiation. were induced until Day 28 and their expression was downregulated on Day 35. This insight improves our current understanding of the role of cytokinin signaling genes in clubroot disease development.