Cytokinin Primes Plant Responses to Wounding and Reduces Insect Performance Christopher Dervinis • Christopher J. Frost • Susan D. Lawrence • Nicole G. Novak • John M. Davis Received: 14 August 2009 / Accepted: 9 December 2009 / Published online: 20 January 2010 Ó Springer Science+Business Media, LLC 2010 Abstract We report a potential role of endogenous cytokinin supply in priming plant defense against herbiv- ory. Cytokinin priming significantly reduced weight gain by insect larvae. Unlike previously described priming by volatile compounds, priming by cytokinin did not over- come 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 mechan- ically wounded source leaves. Cytokinin priming signifi- cantly 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 sig- naling and response pathways may affect plant–herbivore interactions. Keywords Cytokinin Á Priming Á Wounding Á Populus Introduction Priming is a physiological process by which a plant is conditioned for a more rapid or higher-magnitude response to a subsequent event (Bostock 2005; Conrath and others 2006; Frost and others 2008a). With regard to responses against herbivores, the majority of previous work on defense priming has focused on herbivore-induced volatile compounds as priming signals (Engelberth and others 2004; Frost and others 2007; Heil and Silva Bueno 2007; Ton and others 2007), largely in an effort to explain the phenomenon of plant-to-plant communication (Heil and Ton 2008; Frost and others 2008a). However, priming of systemic regions within a plant involves signals within the vasculature as well (Orians 2005; Erb and others 2008; Koornneef and Pieterse 2008). For example, nonadjacent leaves that share direct vascular connection with a wounded leaf show more rapid and/or effective defense responses after damage, relative to leaves without such a vascular connection in Populus (Davis and others 1991; Jones and others 1993; Orians and others 2000; Schittko and Baldwin 2003; Gomez and Stuefer 2006; Frost and others 2007). In addition, prior foliar herbivory and prior root herbivory incite spatially distinct patterns of antiher- bivore defenses within the foliage of Gossypium (Bezemer and others 2003, 2004), implying there may be diverse mechanisms underlying vascular priming. Moreover, the physiological and molecular mechanisms that enable priming are not clear. There is evidence that cytokinin can play a role in integrating diverse environmental stress responses (Hare and others 1997); however, plant responses to wounding Electronic supplementary material The online version of this article (doi:10.1007/s00344-009-9135-2) contains supplementary material, which is available to authorized users. C. Dervinis Á J. M. Davis (&) School of Forest Resources and Conservation, University of Florida, P.O. Box 110410, Gainesville, FL 32611, USA e-mail: jmdavis@ufl.edu C. J. Frost School of Forest Resources, Pennsylvania State University, University Park, PA 16802, USA S. D. Lawrence Á N. G. Novak U.S. Department of Agriculture—Agricultural Research Service, Invasive Insect Biocontrol and Behavior Laboratory, Bldg. 011A, Rm. 214, Beltsville, MD 20705, USA 123 J Plant Growth Regul (2010) 29:289–296 DOI 10.1007/s00344-009-9135-2