Polyribosomes from Pear Fruit

Abstract

Detailed analyses of polysome profiles from Iyophilized pulp tissues of pear fruits (Pyrus communis L. cv. Passe-Crassane) at different stages of ripening and senescence, and estimates of the amount of polysomal-associated mRNA, lead to the conclusions that during senescence (ripening), the ripening and the over-ripening processes can clearly be separated and respectively Unked to the first and the second increase in the large mRNA species. Ethylene synthesis which occurs at the beginning of a normal ripening at 15°C after a cold storage or an ethephon treatment is related to an increase in mRNA and ribosomal material found only in pulp tissues.Finaily, we suggest that in the pear fruit, the sequence of events which occurs during senescence (ripening) is initiated by two systems which regulate ethylene biogenesis, and that the first system is efficient only at low temperatures (from 0 to 4°C).In earlier papers (2, 4), polysome profiles were examined from lyophilized peel tissue of ripening pear (Pyrus communis L. cv. Passe-Crassane), and detailed analyses of polysome distributions were used to measure the amount of polysomal-associated mRNA present in tissues. It has been shown previously (11) that the variety of pear fruit studied in our laboratory required an optimal period of 12 weeks of cold storage before normal ripening at 15°C in which the fruits would exhibit the characteristic climacteric respiratory pattern. Without this prior storage at 0°C, fruits are unable to ripen at 15°C and do not exhibit any climacteric respiration or ethylene synthesis, though an ethylene or ethephon treatment can restore a normal ripening.In this report, we have examined the polyribosome distribution of pulp tissues of fruits ripened in different conditions and estimated the amount of available mRNA. These results have been compared with those obtained from peel tissues sampled from the same fruits in order to follow changes occurring in peel and pulp tissues during ripening and senescence. MATERIALS AND METHODSFruits. Pear (Pyrus communis L. cv. Passe-Crassane) harvested at the beginning of November were stored either at 0°C or at 15°C. Fruits stored at 0°C for 12 weeks were subsequently transferred to 15°C for ripening, while fruits stored initially at 15°Cwere placed either in air or in air with ethylene (500 ,ul/l; continuous flow) (11). Other fruits have been treated by ethephon (2-chloroethylphosphonic acid) at 0.2%

Polyribosomes from Aging Apple and Cherry Fruit

“…After the climacteric peak, apples exhibit two syntheses of mRNA while pears exhibit only one (6). It should be noted, moreover, that the postclimacteric phase is longer in apple than in pear.…”

“…This behavior matches that of the Passe-Crassane fruit in which ethylene biogenesis is regulated by two systems. The first system is inactive at 15°C, while the second one, which is related to a burst in mRNA and ribosome production in pulp tissues, is active in a wider range of temperatures and is followed by ethylene synthesis and by the respiratory crisis (6).…”

“…When apples are harvested 100 d after bloom and stored in air at 15°C, they do not ripen ( 16 (6). Early harvested apples may well require a cold storage before ripening at 1 5C.…”

“…In previous papers (5,6), the amount of polyribosomes was determined in Passe Crassane pear fruits tissues, at different ripening stages, allowing an estimation of the rate of protein synthesis. In this report, we have examined changes in the polyribosomes of Golden Delicious apple and Bigareau Napoleon cherry during ripening.…”

Precondition of 'D' Anjou' Pears for Early Marketing by Ethylene Treatment

“…winter pear cultivars, require a period of chilling to induce normal ripening capacity (Blankenship and Richardson 1985;Drouet and Hartmann 1979;Knee 1987;Leblond and Ularich 1973;Morin et al 1985). Our previous study showed that 'd'Anjou' fruit harvested at commercial maturity with flesh firmness between 66."…”