Cytokinin Primes Plant Responses to Wounding and Reduces Insect Performance

We report a potential role of endogenous cytokinin supply in priming plant defense against herbivory. Cytokinin priming significantly reduced weight gain by insect larvae. Unlike previously described priming by volatile compounds, priming by cytokinin did not overcome vascular restrictions on systemic wound signaling. However, similar to priming by volatile compounds, cytokinin priming occurred upstream of accumulation of jasmonic acid and its precursor linolenic acid in mechanically wounded source leaves. Cytokinin priming significantly altered wound-induced accumulation of transcripts encoding homologs of allene oxide synthase, trypsin inhibitor, and chitinase. Cytokinin priming may reflect coordination between aboveground inducible defense against herbivory and belowground processes such as nutrient availability. These findings should encourage investigations of how genetic alterations in cytokinin signaling and response pathways may affect plant-herbivore interactions.