title: Density-dependent interference of aphids with caterpillar-induced defenses in Arabidopsis: involvement of phytohormones and transcription factors.
abstract: In nature, plants are exposed to attacks by multiple herbivore species at the same time. To cope with these attacks, plants regulate defenses with the production of hormones such as salicylic acid (SA) and jasmonic acid (JA). Because herbivore densities are dynamic in time, this may affect plant-mediated interactions between different herbivores attacking at the same time. In Arabidopsis thaliana, feeding by Brevicoryne brassicae aphids interferes with induced defenses against Plutella xylostella caterpillars. This is density dependent: at a low aphid density, the growth rate of P. xylostella was increased, whereas caterpillars feeding on plants colonized by aphids at a high density have a reduced growth rate. Growth of P. xylostella larvae was unaffected on sid2-1 or on dde2-2 mutant plants when feeding simultaneously with a low or high aphid density. This shows that aphid interference with caterpillar-induced defenses requires both SA and JA signal transduction pathways. Transcriptional analysis revealed that simultaneous feeding by caterpillars and aphids at a low density induced the expression of the SA transcription factor gene WRKY70 whereas expression of WRKY70 was lower in plants induced with both caterpillars and a high aphid density. Interestingly, the expression of the JA transcription factor gene MYC2 was significantly higher in plants simultaneously attacked by aphids at a high density and caterpillars. These results indicate that a lower expression level of WRKY70 leads to significantly higher MYC2 expression through SA-JA cross-talk. Thus, plant-mediated interactions between aphids and caterpillars are density dependent and involve phytohormonal cross-talk and differential activation of transcription factors.
authors.affiliation: Laboratory of Entomology, Wageningen University, Radix building, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands.
authors.forename: Anneke
authors.initials: A
authors.lastname: Kroes
authors.affiliation: Laboratory of Entomology, Wageningen University, Radix building, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands.
authors.forename: Joop J A
authors.initials: JJ
authors.lastname: van Loon
authors.affiliation: Laboratory of Entomology, Wageningen University, Radix building, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands marcel.dicke@wur.nl.
authors.forename: Marcel
authors.initials: M
authors.lastname: Dicke
mesh_terms: D000818:Animals; D001042:Aphids / Q000254:growth & development / Q000502:physiology*; D017360:Arabidopsis / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D060434:Herbivory; D006790:Host-Parasite Interactions; D009036:Moths / Q000254:growth & development / Q000502:physiology*; D054883:Oxylipins / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology*; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000502:physiology; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome
chemical_list: D029681:Arabidopsis Proteins; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D003517:Cyclopentanes; C473611:MYC2 protein, Arabidopsis; D054883:Oxylipins; D010937:Plant Growth Regulators; D014157:Transcription Factors; C487183:WRKY70 protein, Arabidopsis; C011006:jasmonic acid; D020156:Salicylic Acid
keywords: Arabidopsis thaliana; Brevicoryne brassicae; Density dependence; Gene expression; Hormone cross-talk; Plutella xylostella