The genomic sequence of AFS-1―an alpha -farnesene synthase from the apple cultivar ‘Royal Gala’

Abstract

The genomic sequence encoding alpha- farnesene synthase-1 (AFS-1) was amplified from genomic DNA isolated from ‘Royal Gala’ apple (Malus×domestica Borkh.). The genomic sequence consists of six introns and seven exons, which is consistent with Class III terpene synthases. Four variants of the genomic sequence were amplified. The four variants are based on the presence or absence of a repeat of two sequences, one found in intron 4 (CAGTTATTTAATT) and the other in intron 5 (TA). Although there were small nucleotide differences among the three apple cultivars ‘Royal Gala’, ‘Idared’, and ‘Ralls’, these resulted in only two amino acid changes in the protein sequence, which are unlikely to explain the resistance or susceptibility of an apple cultivar to superficial scald. Given that AFS-1 transcript levels are high in all cultivars, it appears that it is either the reactions downstream of alpha-farnesene production that control the accumulation of oxidation products related to superficial scald or that the variation in the level of its substrate, farnesyl diphosphate, may cause differences in the amount of alpha-farnesene produced.

Keywords

α-farnesene synthase / ‘Royal Gala’ / genomic sequence / superficial scald