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Title: PECTATE LYASE GENE EXPRESSION AND ENZYME ACTIVITY IN RIPENING BANANA FRUIT

Author
item MARIN-RODRIGUEZ, M.C. - HORT.RES.INTER.,UK
item Smith, David
item MANNING, K. - HORT.RES.INTER.,UK
item ORCHARD, J. - UNIV. OF GREENWICH,UK
item SEYMOUR, G.B. - HORT. RES.INTER.,UK

Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: The most important processes related to quality of fruit are changes in texture, color, taste, and aroma which occur during ripening. Because of the critical relationship that changes in texture have to quality and postharvest shelf-life, we are studying mechanisms involved in fruit softening. Although fruit softening may involve many changes, it is generally assumed that cell wall(sugar envelope surrounding plant cells) disassembly leading to a loss of wall integrity is a critical feature. If the changes in the cell wall can be stopped or altered, we should be able to create fruit that can last longer on the shelf and possibly be more disease resistant. Previous research showed that pectate lyase is the most active cell wall-degrading enzyme during banana fruit ripening. Therefore, we suspect that pectate lyase activity may play a significant role in fruit softening. The work described in this manuscript involves identification and characterization of a pectate lyase gene and its corresponding protein. This work will allow us to directly evaluate this gene's role in fruit softening. Growers, produce marketers and consumers should all benefit from any improvement in the quality and/or shelf life of fruits.

Technical Abstract: Two distinct cDNA clones showing sequence homology to higher-plant pectate lyase (Pel) genes were isolated from ripening banana fruits. The transcripts were expressed only in fruit tissue and both were strongly ripening-related. Yeast transformation with the most highly expressed Pel clone produced a recombinant protein with pectate lyase activity, demonstrating that this sequence was likely to encode a pectate lyase protein in planta. An assay developed for measuring the action of the endogenous enzyme from banana pulp tissue revealed a significant increase in calcium-dependent pectate lyase activity during ripening. The enhanced levels of enzyme activity corresponded with an increase in extractable soluble polyuronides from banana pulp.