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Two expansin cDNAs from #Prunus armeniaca" expressed during fruit ripening are differently regulated by ethylene

Mbéguié-A-Mbéguié D., Gouble B., Gomez R.M., Audergon J.M., Albagnac G., Fils-Lycaon B.. 2002. Plant Physiology and Biochemistry, 40 (5) : p. 445-452.

DOI: 10.1016/S0981-9428(02)01391-8

Little is known about gene expression during fruit ripening of apricot (Prunus armeniaca L. cv. Bergeron), especially for enzymes involved in cell wall modifications. A partial cDNA clone encoding a protein homologous to expansin was isolated from a ripe apricot fruit cDNA library. This clone was used to isolate two full-length expansin cDNAs, Pa-Exp1 (accession no. U93167) and Pa-Exp2 (accession no. AF038815) from the same cDNA library. The predicted polypeptides encoded by these two cDNAs are different and belong to the [alpha]-expansin family; Pa-Exp1 and Pa-Exp2 are two different members of a multigene family. These two clones are mostly expressed in fruit, during its ripening. Pa-Exp1 mRNA accumulated abundantly at the half-ripe stage of fruit development and decreased thereafter. Pa-Exp2 mRNA level increased from the immature-green stage to the half-ripe stage where it peaked before declining. During the ripening process, Pa-Exp1 and Pa-Exp2 gene expression appeared to be positively correlated with fruit size. Post-harvest treatments by air, ethylene, and 1-methyl cyclopropene led us to conclude that Pa-Exp1 appears to be developmentally down-regulated by ethylene while Pa-Exp2 is not affected. The relationship between Pa-Exp1, Pa-Exp2 and the softening process is also discussed.

Mots-clés : prunus armeniaca; adn; paroi cellulaire; Éthylène; expression des gènes; mûrissage; physiologie après récolte; enzyme; banque de gènes; stade de développement végétal; lutte après récolte

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