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

The effect of ethylene regulation on alpha-farnesene biosynthesis in precrimateric 'Delicious' and 'Granny Smith' apples was studied using an ethylene inducer and inhibitor, alpha-farnesene biosynthesis precursors, and protein transcription and translation inhibitors, alpha-Farnesene was not detectable when internal ethylene concentrations were less than 1 mu l l(-1). Correlations between internal ethylene and alpha-farnesene production fit the exponential growth equation and were significant in 'Delicious' (y = e(0.17); r(2) = 0.68) and 'Granny Smith' (y = e(0.18); r(2) = 0.83). When applied at harvest, aminoethoxyvinylglycine (AVG) at 200 mg l(-1) inhibited both internal ethylene accumulation and alpha-farnesene production, whereas ethephon at 200 mg l(-1) accelerated both. Adding ethephon to AVG-treated fruit after 18 days at 20 degrees C induced internal ethylene accumulation and alpha-farnesene production. Ethephon induced alpha-farnesene production in discs from preclimacteric fruit peel as well as AVG-treated fruit peel, but alpha-farnesene was undetectable when cycloheximide (CHI, 50 mM), actinomycin D (Act D, 50 mM), or silver nitrate (150 mg l(-1)) were added to the ethephon-treated discs. In preclimacteric fruit discs at harvest, with or without AVG treatment, alpha-farnesene biosynthesis was induced by 50 mu M 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 alpha-farnesene by MAL or FPP. (C) Published by Elsevier Science B.V.