Figure 7.
Expression analysis of aamt genes in comparison with methyl anthranilate accumulation and AAMT activity after herbivore damage. Plants were treated with S. littoralis larvae caged for 30 min on a single leaf. Leaf material was harvested at different time points after feeding and was split into equal parts for the different analyses. Means and se are shown (n = 4). A, Methyl anthranilate accumulation after herbivore damage in maize leaves. Leaf material was extracted with hexane, and the extracts were analyzed using GC-MS. B, AAMT activity in herbivore-damaged maize leaves. Plant crude protein extracts were incubated with the methyl group donor [14C]SAM and anthranilic acid. The formed methyl ester was extracted from the assays and quantified using a scintillation counter. C to E, Transcript accumulation of aamt1 (C), aamt2 (D), and aamt3 (E) after herbivore damage. Expression was analyzed using quantitative PCR. The relative expression levels were calculated as the expression levels of the respective genes divided by the geometric mean of the expression levels of the two reference genes (for details, see “Materials and Methods”).