Isolation of ESTs from cacao (Theobroma cacao L.) leaves treated with inducers of the defense response
Pathogenic diseases represent a major constraint to the growth and yield of cacao (Theobroma cacao L.). Ongoing research on model plant systems has revealed that defense responses are activated via signaling pathways mediated by endogenous signaling molecules such as salicylic acid, jasmonic acid and ethylene. Activation of plant defenses is associated with changes in the expression of large numbers of genes. To gain a better understanding of defense responses in cacao, we have employed suppressive subtractive hybridization (SSH) cDNA libraries, macroarray hybridization analysis, high throughput DNA sequencing and bioinformatics to identify cacao genes induced by these signaling molecules. Additionally, we investigated gene activation by a phytotoxic elicitor-like protein, Nep1. We have identified a unigene set of 1,256 members, including 330 members representing genes induced during the defense response.
KeywordsTheobroma cacao Defense Salicylic acid Methyl jasmonate Ethylene Nep1
We would like to thank Marlin Druckenmiller for help in sequencing, Kerr Wall and Alexander Richter for help in bioinformatics, Craig Praul for help with macroarray screening, and Sharon Pishak and other members of the Guiltinan lab for their invaluable contributions. In addition, we thank Masterfoods for providing their EST sequences. This work was supported in part by the American Cocoa Research Institute Endowed Program in the Molecular Biology of Cocoa, by Grants to M.J.G. from the American Cocoa Research Institute, the United States Department of Agriculture Office of International Research Programs, and from the Agricultural Experiment Station of The Pennsylvania State University (CRIS 3550).
Table 1 Annotations and BLAST scores for cacao leaf unigene sequences representing candidate genes whose expression is upregulated by inducers of the defense response
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