Differential regulation of ACC synthase genes in cold-dependent and -independent ripening in pear fruit

I. El-Sharkawy, B. Jones, L. Gentzbittel, J. M. Lelièvre, J. C. Pech, A. Latché

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Late pear cultivars such as Passe-Crassane (PC) require a long chilling treatment before they are capable of ripening. Early cultivars such as Old-Home (OH) have no cold prerequisite. The regulation of 1-aminocyclopropane-1- carboxylic acid synthase (ACS) genes was studied in OH, PC and in OH x PC hybrids in order to determine the role of this gene family in the cold requirement. Of the seven Pc-ACS cDNAs isolated, four (Pc-ACS1a/b and Pc-ACS2a/b) showed differential expression associated with the cold requirement. Pc-ACS1a transcripts accumulated throughout the cold treatment and, with Pc-ACS2a, during ripening of cold-dependent cultivars. Pc-ACS1b and Pc-ACS2b were detected only during ripening of cold-independent genotypes. Furthermore, Pc-ACS2a transcript accumulation was negatively regulated by ethylene, whereas Pc-ACS2b was positively regulated by the hormone. Pc-ACS3, 4 and 5 transcript accumulation was similar in all genotypes. Genetic analyses of OH, PC, and 22 OH x PC progenies demonstrated that late, cold-dependent cultivars were homozygous for Pc-ACS1a and 2a whereas early, cold-independent cultivars were heterozygous for Pc-ACS1(a/b) and homozygous for Pc-ACS2b. A model is presented in which differences in Pc-ACS alleles and gene expression between cold- and non-cold-requiring pears are critical in determining the ripening behaviour of the cultivars.

Original languageEnglish
Pages (from-to)1197-1210
Number of pages14
JournalPlant, Cell and Environment
Issue number10
Publication statusPublished - Oct 2004
Externally publishedYes


  • 1-aminocyclopropane-1- carboxylic acid synthase (ACS) alleles
  • 1-aminocyclopropane-1-carboxylic acid (ACC)
  • ACS isoforms
  • Cold requirement
  • Pear fruit ripening
  • System 1 and system 2 ethylene production


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