Poster: Cell Walls

Abs # 288: Peach mealiness and its association with expansin and pectolytic enzyme activity.

Presenter:	Obenland, David M., dobenlan@qnis.net
Authors	Obenland, David M. (A)   Carroll, Tanya R. (A)
Affiliations:	(A): Horticultural Crops Research Laboratory, USDA/ARS, Fresno, CA

Mealiness, a severe storage disorder of stone fruit, is thought to occur due to alterations in pectolytic enzyme activities. Evidence exists that the protein expansin may mediate the manner in which pectolytic enzymes are allowed access to cell wall substrates. Peach tissue was separated into regions that were mealy or juicy and the individual samples quantified for expansin by use of LeExp1 expansin antibodies. This tissue was also assayed for the activities of polygalacturonase and pectinmethylesterase, two key pectolytic enzymes. The quantity of expansin present in mealy tissue was approximately 50% less than that found in juicy tissue. Exo- and endopolygalacturonase activities were reduced by 65% and 86%, respectively, in the mealy tissue as compared to the juicy. Pectinmethylesterase activity, on the other hand, was nearly the same in the two tissue types. The results support the notion that a change or imbalance in pectolytic activity is related to the development of mealiness and also are suggestive of a possible role for expansin in the development of peach mealiness.