"Influence of plant growth regulators on polygalacturonase expression in strawberry fruit".

VILLARREAL NATALIA M.; MARTINEZ GUSTAVO A.; CIVELLO PEDRO M.

PLANT SCIENCE

ELSEVIER IRELAND LTD

Lugar: Amsterdam; Año: 2009 vol. 176 p. 749 - 757

0168-9452

Strawberry (Fragaria ananassa Duch.) fruit undergoes extensive softening during ripening due to cellwall disassembly, caused by a coordinated action of cell wall proteins and enzymes includingpolygalacturonases (PGs). The influence of plant growth regulators on PG activity and expression of thecorresponding genes has been scarcely analyzed. In this work, the immuno-detection of PG protein(FaPG1) during ripening of strawberry cultivars with contrasting firmness is reported. Two proteins wererecognized with molecular mass of 45?50 kDa, which accumulate from 25% red stage in the firmercultivar (Camarosa) and from white stage in the softer (Toyonoka). The presence of two immunoreactivebands is apparently the product of the differential glycosylation of the same polypeptide. In addition, theeffect of different plant growth regulators on the expression of polygalacturonase gene, accumulation ofFaPG1, and PG activity was analyzed. The treatment with naphthalene acetic acid (NAA) delayedripening and anthocyanin accumulation, reduced the expression of FaPG1 and T-PG, the accumulation ofFaPG1 protein, and decreased PG activity. The application of ABA increased slightly the expression of PGtranscripts, but did not modify significantly the enzyme activity. The treatment with GA3 reducedanthocyanin accumulation and PG activity, though did not produce remarkable effects on the expressionof FaPG1 and T-PG. Anthocyanins increased after treatment with ethephon (ethylene releasing reagent)or sodium nitroprusside (NO providing reagent). The expression of FaPG1 and T-PG increasedconsiderably in response to ethylene and NO. Western-blot data confirmed the trends observed in theexpression analysis in response to ethephon and NO, but PG activity was not modified by any of thesetreatments. However, the application of 1-MCP reduced PG activity, suggesting that ethylene could playa role in the regulation of polygalacturonase expression during strawberry fruit ripening.