Development of Ethylene Biosynthesis in Pear Fruits at —1 °C

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Abstract
Knee, M. 1987. Development of ethylene biosynthesis in pear fruits at — 1 °C.—J. exp. Bot. 38: 1724–1733. The regulation of ethylene synthesis in pear fruits was investigated. During storage for 60 d at — 1 °C the rate of ethylene synthesis increased 100-fold but the concentration of 1-aminocyclopropane-l-carboxylic acid (ACC) increased only 2-fold and ACC synthase activity was low. On transfer to 15 °C after storage at — 1 °C ethylene synthesis increased 10-fold within 10 h but ACC synthase activity only increased rapidly after 24 h; the decline in ACC levels during the first 16 h at 15 °C was insufficient to sustain ethylene synthesis. Ethylene synthesis was further investigated using discs cut from the mid cortex of pear fruits. Synthesis was inhibited by aminoethoxyvinylglycine (AVG) and amino-oxyacetic acid at all stages of ripening. The rate of synthesis and ACC synthase activity increased rapidly after slicing of pears held at — 1 °C but more slowly in discs cut from pears immediately after harvest. Cycloheximide (CHI) inhibited these increases and reversed increases resulting from pre-incubation of discs. A combination of CHI and AVG abolished the capacity of discs to synthesize ACC and ethylene production was curtailed. Cordycepin and actinomycin-D were less effective as inhibitors of the development of ethylene synthesis and ACC synthase activity than as inhibitors of incorporation of 5-[3H] uridine into total RNA or poly A rich RNA. The ability of discs to develop ethylene synthesis and ACC synthase activity in the presence and absence of cordycepin increased concurrently during storage of whole fruits at — 1 °C. This suggested that mRNA for ACC synthase was formed at — 1 °C.