Cytokinins affect plant immunity to various pathogens; however, the mechanisms coupling plant-derived cytokinins to pathogen responses have been elusive. Here, we found that plant-derived cytokinins promote resistance of Arabidopsis to Pseudomonas syringae pv. tomato DC3000 (Pst). Modulated cytokinin levels or signaling activity in CKX- or IPT-overexpressing plants or in ahk2 ahk3 mutants correlated with altered resistance. In fact, the cytokinin-activated transcription factor ARR2 contributes specifically to Pst resistance. The salicylic acid (SA) response factor TGA3 binds ARR2, and mutation of TGA-binding cis-elements in the Pr1 promoter abolished cytokinin- and ARR2-dependent Pr1 activation. Cytokinin treatment did not increase pathogen resistance in tga3 plants, as the cytokinin-dependent induction of Pr1 was eliminated. Moreover, SA signaling enhanced binding of ARR2/TGA3 to the Pr1 promoter. Taken together, these results show that cytokinins modulate the SA signaling to augment resistance against Pst, a process in which the interaction between TGA3 and ARR2 is important.
Bibliographical noteFunding Information:
We thank Choong-Min Ryu and Kangmin Kim for critical reading of the manuscript. This work was supported by the Korea Research Foundation Grant (KRF-2008-314-C00351) of the MOEHRD, Technology Development Program (309017-5) from Ministry for Food, Agriculture and Fisheries, and a grant (20080401-034-041-008-01-00) from the BioGreen 21 Program. J.C. was a recipient of Brain Korea 21 fellowship.
ASJC Scopus subject areas
- Molecular Biology
- General Biochemistry,Genetics and Molecular Biology
- Developmental Biology
- Cell Biology