Transcriptional response of sugarcane roots to methyl jasmonate Neil I. Bower a,c , Rosanne E. Casu a , Donald J. Maclean c , Antonio Reverter b , Scott C. Chapman a , John M. Manners a, * a CSIRO Plant Industry, Queensland Bioscience Precinct, 306 Carmody Road, St. Lucia, Brisbane, Qld. 4067, Australia b CSIRO Livestock Industries, Queensland Bioscience Precinct, 306 Carmody Road, St. Lucia, Brisbane, Qld. 4067, Australia c Department of Biochemistry and Molecular Biology, The University of Queensland, Brisbane, Qld. 4072, Australia Received 27 August 2004; received in revised form 11 October 2004; accepted 13 October 2004 Available online 10 November 2004 Abstract The effect of methyl jasmonate treatment on gene expression in sugarcane roots signalling between roots and shoots was studied. A collection of 829 ESTs were obtained from sugarcane roots treated with the defence-regulator methyl jasmonate (MJ) treatment. A subset of 747 of these were combined with 4793 sugarcane ESTs obtained from stem tissues in a cDNA microarray and experiments undertaken to identify genes that were induced in roots 24–120 h following treatment with MJ. Two data analysis systems (t-statistic and tRMA) were used to analyse the microarray results and these methods identified a common set of 21 ESTs corresponding to transcripts significantly induced by MJ in roots and 23 that were reduced in expression following MJ treatment. The induction of six transcripts identified in the microarray analysis was tested and confirmed using northern blotting. Homologues of genes encoding lipoxygenase and PR-10 proteins were induced 8– 24 h after MJ treatment while the other four selected transcripts were induced at later time points. Following treatment of roots with MJ, the lipoxygenase homologue, but not the PR-10 homologue, was induced in untreated stem and leaf tissues. The PR-10 homologue and a PR-1 homologue, but not the lipoxygenase homologue, were induced in untreated tissues after the application of SA to roots. Repeated foliar application of MJ had no apparent effects on plant growth and was demonstrated to increase lipoxygenase transcripts in roots, but did not increase transcript levels of other genes tested. These results lay a foundation for further studies of induced pest and disease resistance in sugarcane roots. # 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Sugarcane; Methyl jasmonate; Salicylic acid; Lipoxygenase; PR-10 1. Introduction Soil-borne pathogens and pests pose a particular problem for sugarcane [1]. Breeding resistance to important insect pests such as sugarcane whitegrubs [2] and the oomycete pathogen Pachymetra chaunorhiza[3] is an important objective but difficult because of a lack of highly effective genetic resistance and the difficulties involved in breeding that result from sugarcane’s extreme genetic complexity [4]. Currently, white grubs and other root-attacking insect pests are controlled by the application of toxic pesticides [1]. An attractive approach for the control of soil-borne pathogens and pests would be to harness the natural inducible defence mechanisms of sugarcane. Induced resistance can be manipulated by either the development of very specific agrochemicals [5], application of defence-inducing microbes [6] or via genetic manipulation of defence- signalling pathways through conventional plant breeding or genetic engineering [7]. Induced defence mechanisms and their genetic and physiological control have not been extensively studied in sugarcane, and genes associated with root defences are poorly understood in monocots in general. Jasmonates are important regulators of plant defence, and have been implicated in defence responses to insect pests [8], resistance to necrotrophic microbial pathogens [9]. Resistance to insect pests and oomycete pathogens in the www.elsevier.com/locate/plantsci Plant Science 168 (2005) 761–772 Abbreviations: MJ, methyl jasmonate; SA, salicylic acid; PR, patho- genesis related; PAL, phenylalanine ammonia lyase; DAHP, 3-deoxy-D- arabino-heptulosonate 7-phosphate * Corresponding author. Tel.: +61 7 3214 2304; fax: +61 7 3214 2950. E-mail addresses: neil.bower@csiro.au (N.I. Bower), john.manners@csiro.au (J.M. Manners). 0168-9452/$ – see front matter # 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.plantsci.2004.10.006