<p> Pierce’s disease (PD), caused by bacterium Xylella fastidiosa, seriously hampers the cultivation of <i>Vitis vinifera</i> also known as bunch grapes, in different parts of the world. The bacterium clogs xylem vessels and forms a biofilm, resulting in the wilting of the plant. Bunch grape cultivars exhibit certain degree of tolerance to PD, however most commercial cultivars suffer heavy loss due to this devastating disease. Therefore, studies on genetic variation for disease tolerance will assist in identification of key molecular components that confer tolerance to PD. <i>Vitis</i> species, such as, Florida hybrid bunch (FH) and muscadine grape (<i> Vitis rotundifolia</i>) are widely cultivated in southeastern United States, and are known for their tolerance to PD. A detailed proteomic profile study of contrasting grape species is vital to understand the biological molecules associated with the PD tolerance. However information on total protein composition of <i>Vitis xylem</i> and sap is limited. The overall goals of this study are to determine the signal sequences associated with xylem and sap for the delivery of therapeutic proteins to control <i>Xylella fastidiosa. </i> The specific objectives of this research project are: 1) to compare the proteome profiles of xylem tissue and xylem sap from PD tolerant and -susceptible grapevine cultivars, and 2) to determine the role of proteins in the tissue and sap associated with PD tolerance mechanism. In this study, we used Bunch, FH, and Muscadine grape cultivars to characterize differentially expressed and unique proteins. Differentially expressed proteins were identified using LC MS/MS spectrometry searched against <i>Vitis</i> database. A total of 2519 and 402 proteins were identified in xylem and sap respectively, of which 151 proteins were common to both tissues. Bunch, FH, and muscadine sap showed 52, 53, and 30 unique proteins respectively. The cluster dendrogram analysis of the sap proteome showed that all of the <i>Vitis</i> species are bifolious. Based on the aforementioned, Florida hybrid bunch and muscadines are more closely related to each other than to bunch grape. Functional analysis and gene ontology revealed that proteins involved in carbohydrate metabolic process are more abundant in bunch grape, while FH and muscadine grape have more defense related proteins. Therefore, it is plausible to conclude that major functions of sap proteins in Bunch, FH, and Muscadine grapes are carbohydrate metabolic process and proteolysis (23%), protein phosphorylation (38%), and oxidation and reduction process (16%), respectively. Proteins involved in the defense and peroxidase activity are abundantly present in xylem and sap of FH and muscadine, and these proteins are relatively in reduced levels in bunch xylem and sap. Together, our findings highlight the possible roles of the identified unique proteins towards PD tolerance to Florida hybrid bunch and muscadine cultivars.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1594029 |
| Date | 24 October 2015 |
| Creators | Sridhar, Varshini |
| Publisher | Florida Agricultural and Mechanical University |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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