Inhibition of Ethylene Biosynthesis by Aminoethoxyvinylglycine and by Polyamines Shunts Label from 3,4-[14C]Methionine into Spermidine in Aged Orange Peel Discs

Abstract

The flux of radioactivity from 3,4-[14]Cmethionine into S-adenosyl-L-methionine (SAM), 1-aminocyclopropane-1-carboxylic acid (ACC), spermine and spermidine while inhibiting conversion of ACC to ethylene by 100 mM P and 2 mM Co2+ was studied in aged peel discs of orange (C. sinensis L. Osbeck) fruit. Inhibition up to 80% of ethylene production by Pc and Co was accompanied by a 3.3 times increase of label in ACC while the radioactivity in SAM was only slightly reduced. Aminoethoxyvinylglycine (AVG) increased the label in SAM by 61% and reduced it in ACC by 47%. Different combinations of standard solution, in which putrescine or spermidine were administered alone or with AVG, demonstrated clearly that inhibition of ethylene biosynthesis, at the conversion of SAM to ACC, by AVG, exogenous putrescine or exogenous spermidine, stimulated the incorporation of 3,4-[14C]methionine into spermidine.