A Conserved Transcript Pattern in Response to a Specialist and a Generalist Herbivorew⃞

Abstract

Transcript patterns elicited in response to attack reveal, at the molecular level, how plants respond to aggressors. These patterns are fashioned both by inflicted physical damage as well as by biological components displayed or released by the attacker. Different types of attacking organisms might therefore be expected to elicit different transcription programs in the host. Using a large-scale DNA microarray, we characterized gene expression in damaged as well as in distal Arabidopsis thaliana leaves in response to the specialist insect, Pieris rapae. More than 100 insect-responsive genes potentially involved in defense were identified, including genes involved in pathogenesis, indole glucosinolate metabolism, detoxification and cell survival, and signal transduction. Of these 114 genes, 111 were induced in Pieris feeding, and only three were repressed. Expression patterns in distal leaves were markedly similar to those of local leaves. Analysis of wild-type and jasmonate mutant plants, coupled with jasmonate treatment, showed that between 67 and 84% of Pieris-regulated gene expression was controlled, totally or in part, by the jasmonate pathway. This was correlated with increased larval performance on the coronatine insensitive1 glabrous1 (coi1-1 gl1) mutant. Independent mutations in COI1 and GL1 led to a faster larval weight gain, but the gl1 mutation had relatively little effect on the expression of the insect-responsive genes examined. Finally, we compared transcript patterns in Arabidopis in response to larvae of the specialist P. rapae and to a generalist insect, Spodoptera littoralis. Surprisingly, given the complex nature of insect salivary components and reported differences between species, almost identical transcript profiles were observed. This study also provides a robustly characterized gene set for the further investigation of plant-insect interaction.

Variations in CYP74B2 (Hydroperoxide Lyase) Gene Expression Differentially Affect Hexenal Signaling in the Columbia and Landsberg erecta Ecotypes of Arabidopsis

“…But, in the long run, it is the induced levels of glucosinolates that provide the most effective, sustained protection against insect damage. Consistent with this need, CYP83B1 transcripts were shown to be induced in the Col ecotype in response to herbivore attack and JA application, and, inconsistently, CYP83A1 transcripts showed no response to these effectors (Reymond et al, 2004). In showing that the mutant CYP74B2 protein potentially expressed in the Col ecotype is incapable of generating C 6 volatiles and other signaling derivatives even if it was induced, our results provide an explanation for the differential induction of the CYP83A1 and CYP83B1 loci in this earlier study.…”

“…These include 1-aminocyclopropane-1-carboxylate oxidase (At1g12010), which is a protein involved in ethylene synthesis, and cationic peroxidase (At1g30870) and dehydroascorbate reductase (At1g19570), which are both proteins involved in antioxidant defense. The fact that transcripts from these loci are also induced in herbivoredamaged plants (Reymond et al, 2004) and depleted in the Col ecotype suggests that they also exist downstream of the HPL pathway activated in plant-insect interactions. The immediate effects on insect resistance of inactivating the HPL pathway are complexed by the fact that GLVs have the ability to affect herbivore performance both negatively (by reducing feeding rate, repelling oviposition, or attracting predators; Hildebrand et al, 1993;DeMoraes et al, 2001;Kessler and Baldwin, 2001;Vancanneyt et al, 2001) and positively (by serving as feeding stimulants; Halitschke et al, 2004).…”

“…Other LOX loci whose expression patterns do not vary between these ecotypes would be predicted to code for proteins generating substrates for the AOS branch of this pathway and/or metabolize other fatty acid HPs (Leó n et al, 2002;Halitschke and Baldwin, 2003). Underexpression of the LOX2 locus in the Col ecotype, which is induced by both insect damage and JA treatment in other ecotypes (Reymond et al, 2004) and implicated in generating precursors for both branches of the oxylipin pathway, is an especially important example of the autoregulatory cycles operating in this signaling pathway.…”

Intraspecific variation in defense against a generalist lepidopteran herbivore in populations of Eruca sativa (Mill.)

“…are commonly used as a model for generalist and specialist chewing insects, respectively (e.g., Agrawal and Kurashige 2003; Heidel and Baldwin 2004; Reymond et al. 2004; Clauss et al. 2006; Burow et al.…”

“…2004; Bidart‐Bouzat and Kliebenstein 2011). However, specialist insects (e.g., Pieris sp., Pluttela xylostella ) have evolved physiological means to overcome the toxic effects of GS; the deterrent and toxic properties of these metabolites are therefore mostly effective against generalists (Ratzka et al.…”