The role of β-hexosaminidase in peach (Prunus persica) fruit softening

To determine the role of beta-hex in peach fruit softening, we cloned two beta-hexosaminidase (beta-hex) gene homologs, Pphexl and Pphex2. Results showed that the full cDNA length of Pphex1 (JQ979080) was 1859 bp, containing an open reading frame (ORF) with 1689 bp and encoding a polypeptide of 562 amino acides. Pphex2 (JX069961) was 2018 bp in length, containing an ORF with 1794 bp and encoding a polypeptide of 594 amino acides. Pphexl and Pphex2 showed different expression patterns during peach fruit development and storage period. During peach fruit development, the Pphexl expression initially decreased, but later increased towards ripening. However, Pphex2 expression was very low during fruit developmental stage, and then increased significantly towards ripening. During fruit storage, beta-hexosaminidase activity increased in the first 6 days. The expression peak of Pphexl occurred at the second day during storage. Pphex2 showed relative high expression during the whole storage period. Treatment with 2-Acetaindo-1,2-dideoxynojirimycin (2-ADN) caused inhibition in Pphex1 and Pphex2 transcription and p-hexosaminidase activity, at the same time, the rapid decline in fruit firmness was also delayed. Suppression of 2-ADN treated fruits in ethylene production, as well as the expression of PpACO and PpACS, and the activities of cell wall degrading enzymes (endo-PG, exo-PG, PME, and beta-Gal) were also observed. Our study suggests the involvement of beta-hex in the regulation of fruit softening in peach. (C) 2014 Elsevier B.V. All rights reserved.