Expression of expansin gene, MiExpA1, and activity of galactosidase and polygalacturonase in mango fruit as affected by oxalic acid during storage at room temperature

An expansin gene, MiExpA1, from mango fruit (Mangifera indica L. cv. Zill), which had highest homology with MiExpA1 from cv. Dashehari by 96.43% in nucleotide sequence and 95.79% in amino acid sequence, was cloned and characterised. Moreover, effects of oxalic acid on MiExpA1 expression and enzymatic activities of α-galactosidase (α-Gal), β-galactosidase (β-Gal), and polygalacturonase (PG) were investigated after Zill fruit were dipped in 5mM oxalic acid solution for 10min and then stored at 25°C. Application of oxalic acid significantly inhibited decrease in flesh firmness, notably suppressed and delayed MiExpA1 expression in the peel and the flesh, and also significantly decreased activities of these pectolytic enzymes in the flesh. It was suggested that these effects of oxalic acid might collectively contribute to alleviating cell wall disassembly, thereby slowing the process of softening and ripening in mango fruit during storage.