title: The impact of the absence of aliphatic glucosinolates on insect herbivory in Arabidopsis.
abstract: Aliphatic glucosinolates are compounds which occur in high concentrations in Arabidopsis thaliana and other Brassicaceae species. They are important for the resistance of the plant to pest insects. Previously, the biosynthesis of these compounds was shown to be regulated by transcription factors MYB28 and MYB29. We now show that MYB28 and MYB29 are partially redundant, but in the absence of both, the synthesis of all aliphatic glucosinolates is blocked. Untargeted and targeted biochemical analyses of leaf metabolites showed that differences between single and double knock-out mutants and wild type plants were restricted to glucosinolates. Biosynthesis of long-chain aliphatic glucosinolates was blocked by the myb28 mutation, while short-chain aliphatic glucosinolates were reduced by about 50% in both the myb28 and the myb29 single mutants. Most remarkably, all aliphatic glucosinolates were completely absent in the double mutant. Expression of glucosinolate biosynthetic genes was slightly but significantly reduced by the single myb mutations, while the double mutation resulted in a drastic decrease in expression of these genes. Since the myb28myb29 double mutant is the first Arabidopsis genotype without any aliphatic glucosinolates, we used it to establish the relevance of aliphatic glucosinolate biosynthesis to herbivory by larvae of the lepidopteran insect Mamestra brassicae. Plant damage correlated inversely to the levels of aliphatic glucosinolates observed in those plants: Larval weight gain was 2.6 fold higher on the double myb28myb29 mutant completely lacking aliphatic glucosinolates and 1.8 higher on the single mutants with intermediate levels of aliphatic glucosinolates compared to wild type plants.
authors.affiliation: Plant Research International, Wageningen, The Netherlands. jules.beekwilder@wur.nl
authors.forename: Jules
authors.initials: J
authors.lastname: Beekwilder
authors.forename: Wessel
authors.initials: W
authors.lastname: van Leeuwen
authors.forename: Nicole M
authors.initials: NM
authors.lastname: van Dam
authors.forename: Monica
authors.initials: M
authors.lastname: Bertossi
authors.forename: Valentina
authors.initials: V
authors.lastname: Grandi
authors.forename: Luca
authors.initials: L
authors.lastname: Mizzi
authors.forename: Mikhail
authors.initials: M
authors.lastname: Soloviev
authors.forename: Laszlo
authors.initials: L
authors.lastname: Szabados
authors.forename: Jos W
authors.initials: JW
authors.lastname: Molthoff
authors.forename: Bert
authors.initials: B
authors.lastname: Schipper
authors.forename: Hans
authors.initials: H
authors.lastname: Verbocht
authors.forename: Ric C H
authors.initials: RC
authors.lastname: de Vos
authors.forename: Piero
authors.initials: P
authors.lastname: Morandini
authors.forename: Mark G M
authors.initials: MG
authors.lastname: Aarts
authors.forename: Arnaud
authors.initials: A
authors.lastname: Bovy
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000469:parasitology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D005247:Feeding Behavior / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005961:Glucosinolates / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D051548:Histone Acetyltransferases; D006790:Host-Parasite Interactions; D007313:Insecta / Q000502:physiology*; D007814:Larva / Q000502:physiology; D013058:Mass Spectrometry; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D025341:Principal Component Analysis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
chemical_list: D029681:Arabidopsis Proteins; D005961:Glucosinolates; D051548:Histone Acetyltransferases; D014157:Transcription Factors; C523552:Myb29 protein, Arabidopsis; C474636:GCN5 protein, Arabidopsis; D000099224:p300-CBP-Associated Factor