"Polygalacturonase activity and expression of related genes during ripening of strawberry cultivars with contrasting fruit firmness".

VILLARREAL, N; ROSLI, H; MARTINEZ, G; CIVELLO, P

POSTHARVEST BIOLOGY AND TECHNOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2008 vol. 47 p. 141 - 150

0925-5214

Fleshy fruits soften during ripening mainly as a consequence of the catabolism of cell wall components. In strawberry (Fragaria × ananassaDuch), the depolymerization and solubilization of pectins increase during ripening and contribute to fruit softening. In the present paper, we reportthe cloning and expression analysis of two polygalacturonase (PG) putative cDNAs: FaPG1 and T-PG. The former seems to be the same sequenceof previously reported PG in strawberry, while T-PG cDNA has a deletion of 85 bp that cause a frame shift and would produce an inactive protein.Measurement of total PG activity and expression of FaPG1 and T-PG were performed in strawberry cultivars with contrasting softening rates. Thesoftest cultivar (Toyonaka) showed the higher total PG activity in all ripening stages analyzed. The analysis by RT-PCR revealed that both genesexpress in the three cultivars, though the expression pattern was different. In the firmer cultivars (Selva and Camarosa) the expression of T-PG wasconsiderably higher than the expression of FaPG1, while the opposite occurred in the softest cultivar (Toyonaka). Therefore, the higher PG activitydetected in Toyonaka correlates with the enhanced expression of FaPG1 gene, while the low PG activity found in the firm cultivars correlates witha higher expression of T-PG, a gene that could encode a truncated protein without PG activity. The influence of auxins on both the expression ofPG genes and the total PG activity during strawberry fruit ripening was also analyzed.