The impact of the absence of aliphatic glucosinolates on insect herbivory in Arabidopsis.
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.
Beekwilder
Jules
J
Plant Research International, Wageningen, The Netherlands. jules.beekwilder@wur.nl
van Leeuwen
Wessel
W
van Dam
Nicole M
NM
Bertossi
Monica
M
Grandi
Valentina
V
Mizzi
Luca
L
Soloviev
Mikhail
M
Szabados
Laszlo
L
Molthoff
Jos W
JW
Schipper
Bert
B
Verbocht
Hans
H
de Vos
Ric C H
RC
Morandini
Piero
P
Aarts
Mark G M
MG
Bovy
Arnaud
A
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
D029681:Arabidopsis Proteins; D005961:Glucosinolates; D051548:Histone Acetyltransferases; D014157:Transcription Factors; C523552:Myb29 protein, Arabidopsis; C474636:GCN5 protein, Arabidopsis; D000099224:p300-CBP-Associated Factor