Evidence that a-farnesene biosynthesis during fruit ripening is mediated by ethylene regulated gene expression in apples

The effect of ethylene regulation on a-farnesene biosynthesis in preclimateric ‘Delicious’ and ‘Granny Smith’ apples was studied using an ethylene inducer and inhibitor, a-farnesene biosynthesis precursors, and protein transcription and translation inhibitors. a-Farnesene was not detectable when internal ethylene concentrations were less than 1 ml l. Correlations between internal ethylene and a-farnesene production fit the exponential growth equation and were significant in ‘Delicious’ (y=e; r=0.68) and ‘Granny Smith’ (y=e; r=0.83). When applied at harvest, aminoethoxyvinylglycine (AVG) at 200 mg l inhibited both internal ethylene accumulation and a-farnesene production, whereas ethephon at 200 mg l accelerated both. Adding ethephon to AVG-treated fruit after 18 days at 20°C induced internal ethylene accumulation and a-farnesene production. Ethephon induced a-farnesene production in discs from preclimacteric fruit peel as well as AVG-treated fruit peel, but a-farnesene was undetectable when cycloheximide (CHI, 50 mM), actinomycin D (Act D, 50 mM), or silver nitrate (150 mg l) were added to the ethephon-treated discs. In preclimacteric fruit discs at harvest, with or without AVG treatment, a-farnesene biosynthesis was induced by 50 mM mevalonic acid lactone (MAL) or farnesyl pyrophosphate (FPP), but not by hydroxymethylglutaric acid (HMG). Adding CHI or Act D to these discs did not affect the induction of a-farnesene by MAL or FPP. © Published by Elsevier Science B.V.