Papain-Like Cysteine Proteases (PLCPs) are a family of protein degrading enzymes with similar structures and functions, thirty-three of which are found in Carica papaya (C. papaya). Papain, the namesake of the enzyme family, is extensively used in industry and harvested from the latex of un-ripened C. papaya fruits. In addition to its industrial importance, papain, along with other PLCPs, has been observed to harm insects when they consume tissues containing papaya latex. Because of their ability to harm herbivores and their high concentrations in un- ripened fruit, it is hypothesized that these enzymes primarily function as herbivore deterrents. While there have been studies on other members of this enzyme family, none have been conducted on their differential gene expression across sex, tissue type, and developmental stage. The ultimate purpose of this project is to investigate the differential gene expression of five key members of this enzyme family—papain, chymopapain, caricain, glycyl endopeptidase, and RD21A.
Currently, chymopapain’s differential gene expression patterns are being elucidated. This will establish relative gene expression data for future students to utilize when performing differential gene expression on the remaining members of the gene family. Based on the results generated thus far, our hypothesis that chymopapain will be most expressed in the late-stage floral tissue is holding true as there is no observed significant difference between the expression levels of the young male and female tissues. Further differential expression data still needs to be obtained before making final conclusions about chymopapain expression profile between the variables being tested. These research findings will contribute to the knowledge of how plants prioritize the defense of different tissues.
Author(s): William Gregor, Botany Major
Advisor(s): Richard Moore, Department of Biology
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