บทคัดย่องานวิจัย

หมวดหมู่ : ฐานข้อมูลงานวิจัย

Patterns of temporal mRNA expression and enzyme activity of pectolytic and non-pectolytic cell-wall degrading enzymes in growth and ripening of apple fruits.

Goulão L., Oliveira C.M.

5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004. page 6

2004

บทคัดย่อ

Patterns of temporal mRNA expression and enzyme activity of pectolytic and non-pectolytic cell-wall degrading enzymes in growth and ripening of apple fruits.  Textural changes that lead to softening of apples are accompanied by enzymatic degradation and loss of neutral sugars of the pectic polysaccharides of the cell wall.Recently, it has been suggested that the process is the result of the combined action of several cell wall degrading enzymes.This work aims to establish a temporal sequence of the action of cell wall degrading enzymes during apple growth and ripening.

A cDNA library enriched with mRNA isolated from over-ripe fruits was constructed and screened to clone an endo-1,4-beta-glucanase (EGase), two xyloglucan endotranslycosylase / hydrolase (XTH), an expansin, an alpha-L-arabinofuranosidase (Afase), a pectin methylesterase (PME), and a pectate lyase (PL) full-length cDNAs encoding late isoforms.These clones were characterised and their accumulation during fruit growth and ripening was examined by semi-quantitative RT-PCR analyses.Expression of beta-galactosidase and polygalacturonase (PG) mRNAs previously reported was also included in the analyses.Transcripts of all enzymes, except PME, could be detected in fruits at harvest.However, transcripts of Egase were more abundant at fruit set and both expansin and pectate lyase had their highest expression before ripening.The stronges expression in over-ripe fruits was observed for beta-galactosidase and PG clones.RT-PCR analyses were also conducted in flowers, peduncles, young and expanded leaves and senescent petioles, and the results showed that the cloned cDNAs are not fruit-specific.

The activity for each enzyme was also monitored in fruits at the same stages as for the mRNA accumulation.Comparison of the patterns of enzyme activity with mRNA expression suggests the presence of isoforms acting in fruit growth and ripening-specific isoforms or post-transcriptional regulation.Furthermore, the results indicate that the pattern of softening of apple fruits is different from the model plant tomato.