Fennel (Foeniculum vulgare Mill.), a medicinal plant from the Apiaceae, is used in traditional medicine. For the first time in F. vulgare, partial cDNA of two key genes of the t-anethole biosynthetic pathway, phenylalanine ammonia-lyase (PAL), and t-anol/isoeugenol synthase (IGS1), was identified and characterized. Also, the expression patterns of both genes, t-anethole accumulation, total phenolics, and total flavonoid content were evaluated in two Iranian fennel genotypes under various methyl jasmonate (MeJA) treatments. Multiple alignment analysis of the PAL and IGS1 amino acid sequences of fennel revealed a high degree of similarity to PAL and IGS1 amino acid sequences of plant species belonging to the Apiaceae family. Our findings also revealed that the PAL and IGS1 genes expressed differently in two fennel genotypes, and their expression varied depending on MeJA concentration and time point. The maximum expression of the PAL and IGS1 genes was observed in the Shiraz genotype under treatment with 100 µM MeJA for 24 h, which was 5.83 and 5.09 times that of their controls, respectively. Leaves of both Shiraz and Hamedan genotypes treated with 100 µM MeJA for 24 h had the highest content of t-anethole (34.05 and 10.45 µg/g DW, respectively), total phenolic content (202.35 and 34.61 mg TAE/g DW, respectively), and total flavonoid content (19.48 and 7.25 mg QUE/g DW, respectively), which was consistent with the expression patterns of the two identified genes. The findings of this study will be useful in future molecular and functional studies of the t-anethole biosynthetic pathway in fennel.
