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2. Characterization of a calcium/calmodulin-regulated SR/CAMTA gene family during tomato fruit development and ripening

Author

Yang Tianbao, Peng Hui, Whitaker Bruce D, and Conway William S

Subjects
Botany, QK1-989
Abstract

Abstract Background Fruit ripening is a complicated development process affected by a variety of external and internal cues. It is well established that calcium treatment delays fruit ripening and senescence. However, the underlying molecular mechanisms remain unclear. Results Previous studies have shown that calcium/calmodulin-regulated SR/CAMTAs are important for modulation of disease resistance, cold sensitivity and wounding response in vegetative tissues. To study the possible roles of this gene family in fruit development and ripening, we cloned seven SR/CAMTAs, designated as SlSRs, from tomato, a model fruit-bearing crop. All seven genes encode polypeptides with a conserved DNA-binding domain and a calmodulin-binding site. Calmodulin specifically binds to the putative targeting site in a calcium-dependent manner. All SlSRs were highly yet differentially expressed during fruit development and ripening. Most notably, the expression of SlSR2 was scarcely detected at the mature green and breaker stages, two critical stages of fruit development and ripening; and SlSR3L and SlSR4 were expressed exclusively in fruit tissues. During the developmental span from 10 to 50 days post anthesis, the expression profiles of all seven SlSRs were dramatically altered in ripening mutant rin compared with wildtype fruit. By contrast, only minor alterations were noted for ripening mutant nor and Nr fruit. In addition, ethylene treatment of mature green wildtype fruit transiently stimulated expression of all SlSRs within one to two hours. Conclusions This study indicates that SlSR expression is influenced by both the Rin-mediated developmental network and ethylene signaling. The results suggest that calcium signaling is involved in the regulation of fruit development and ripening through calcium/calmodulin/SlSR interactions.

Published
2012
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3. Biocontrol of food-borne pathogens Listeria monocytogenes and Salmonella enterica serovar Poona on fresh-cut apples with naturally occurring bacterial and yeast antagonists

Author

Leverentz, Britta, Conway, William S., Janisiewicz, Wojciech, Abadias Maribel, Kurtzman, Cletus P., and Camp, Mary J.

Subjects
Listeria monocytogenes -- Research, Apple -- Contamination, Foodborne diseases -- Causes of, Biological sciences
Abstract

Fresh-cut apples contaminated with either Listeria monocytogenes or Salmonella enterica serovar Poona, using strains implicated in outbreaks, were treated with one of 17 antagonists originally selected for their ability to inhibit fungal post harvest decay on fruit. While most of the antagonists increased the growth of the food-borne pathogens, four of them proved effective in preventing the growth or survival of food-borne human pathogens on fresh-cut apple tissue.

Published
2006

4. Biocontrol of Listeria monocytogenes on fresh-cut produce by treatment with lytic bacteriophages and a bacteriocin

Author

Leverentz, Britta, Conway, William S., Camp, Mary J., Janisiewicz, Wojciech J., Abuladze, Tamuna, Yang, Ming, Saftner, Robert, and Sulakvelidze, Alexander

Subjects
Bacteriocins -- Physiological aspects, Bacteriophages -- Physiological aspects, Bacteriophages -- Environmental aspects, Listeria monocytogenes -- Physiological aspects, Listeria monocytogenes -- Environmental aspects, Listeria monocytogenes -- Growth, Microbial contamination -- Environmental aspects, Microbial contamination -- Prevention, Microbial populations -- Environmental aspects, Microbial populations -- Physiological aspects, Microbiology -- Research, Microbiology -- Environmental aspects, Company growth, Biological sciences
Abstract

The authors describe their study of Listeria monocytogenes. They have determined the survival and growth of L. monocytogenes on fresh-cut honeydew melon and apple slices at an abusive temperature, and have investigated the effectiveness of lytic phages in controlling L. monocytogenes contamination on fresh-cut fruits.

Published
2003

6. Purification and Biochemical Characterization of Polygalacturonase Produced by Penicillium expansum During Postharvest Decay of 'Anjou' Pear

Author

Jurick, Wayne M., II, Jurick, Wayne M., II, Vico, Ivana, Gaskins, Verneta L., Garrett, Wesley M., Whitaker, Bruce D., Janisiewicz, Wojciech, Conway, William S., Jurick, Wayne M., II, Jurick, Wayne M., II, Vico, Ivana, Gaskins, Verneta L., Garrett, Wesley M., Whitaker, Bruce D., Janisiewicz, Wojciech, and Conway, William S.

Abstract

A polygalacturonase (PG) was extracted and purified from decayed tissue of 'Anjou' pear fruit inoculated with Penicillium expansum. Ammonium sulfate precipitation, gel filtration, and cation exchange chromatography were used to purify the enzyme. Both chromatographic methods revealed a single peak corresponding to PG activity. PG enzyme activity from healthy and wounded pear tissue was undetectable, which supports the claim that the purified PG is of fungal origin. The purified enzyme had a molecular mass of 41 kDa and a pI of 7.8. Activity of the PG was not associated with a glycosylated protein. The enzyme was active over a broad pH range from 3 to 6, with optimal activity at 4.5 in sodium citrate and sodium acetate buffers. The optimal temperature for activity was 37 degrees C but the enzyme was also active at 0, 5, 10, 20, and 50 degrees C. Thin-layer chromatographic analysis of PG hydrolysis products showed that the enzyme exhibits endo- and exo-activity. The purified enzyme macerated tissue in vitro causing approximate to 30% reduction in mass of pear plugs compared with approximate to 17% reduction for apple. Additionally, it produced 1.5-fold more soluble polyuronides on pear than apple tissue. This work shows for the first time the production of a PG by P. expansum during postharvest decay of pear fruit is different from the previously described PG produced in decayed apple fruit by the same pathogen.

Published
2010

7. Isolation, Purification, and Characterization of a Polygalacturonase Produced in Penicillium solitum-Decayed 'Golden Delicious' Apple Fruit

Author

Jurick, Wayne M., II, Jurick, Wayne M., II, Vico, Ivana, McEvoy, James L., Whitaker, Bruce D., Janisiewicz, Wojciech, Conway, William S., Jurick, Wayne M., II, Jurick, Wayne M., II, Vico, Ivana, McEvoy, James L., Whitaker, Bruce D., Janisiewicz, Wojciech, and Conway, William S.

Abstract

Polygalacturonase (PG) was extracted and purified from decayed 'Golden Delicious' apple fruit inoculated with Penicillium solitum. Ammonium sulfate, gel filtration, and cation exchange chromatography were used to purify the enzyme. Both chromatographic methods revealed a single peak corresponding to PG activity. The purified PG most likely originates from the fungus because PG activity from healthy and wounded apple tissue was undetectable. Analysis of cation exchange-purified material using sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a single 50-kDa band. The enzyme was active over a broad pH range (3 to 7), with optimal activity between pH 4 and 5. PG was highly active at 20 and 37 degrees C but was also detectable at 2, 50, and 75 degrees C. Divalent cations affected PG enzyme activity; Mg and Fe increased, whereas Ca and Mn reduced activity in vitro. Thin-layer chromatographic separation of hydrolysis products and data from a PG plate activity assay based on staining with ruthenium red showed that the enzyme exhibits both exo and endo activity. Purified PG incubated with intact apple fruit tissue in vitro caused a 30% reduction in mass after 48 h, suggesting a role in P. solitum-mediated decay of apple fruit.

Published
2009

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