Location: Sustainable Perennial Crops
2013 Annual Report
Identification of genes involved in plant defense is a first critical step in understanding how plants resist infection from plant pathogens and respond to stress in general. ARS will use microarray technology to identify cacao transcripts responsive to pathogen infection in resistant and susceptible cacao clones. Total RNA will be isolated from cacao tissues. These samples will be hybridized to the full transcriptome microarray available at The Pennsylvania State University. Cacao genes showing differential expression patterns in association with the cacao resistance response will be identified and functionally analyzed.
The functional analyses of specific genes involved in plant defense will be critical as the genomics capabilities available for cacao research expand. Identifying the exact function of genes considered important in plant defense will allow their exploitation in traditional and advanced breeding efforts to develop cacao materials resistant to the negative effects of stress. Cacao will be both constitutively and transiently transformed to overexpress genes of potential importance to plant defense. The transformed materials will be evaluated under conditions of stress, including disease to validate their importance in the defense process. The proposed research parallels objectives within the associated main project.
2)RNA from mycelium and.
3)RNA from sporulating cultures. Preliminary data analysis has been conducted and confirms that a very deep and reasonably complete assembly of the genome has been produced. All assembly and quality statistics are good, although the number of contigs is still very large. Microarrays were used in a series of experiments to explore the gene expression during pathogen infection and in response to treatment with salicylic acid, a defense signaling molecule. A large set of genes that are co-regulated during these responses were identified. The promoters of three of these genes were isolated to study the mechanisms involved in the regulation of the defense response of cacao. Using a recently developed cacao transient gene-expression assay method, the functions of several candidate genes that function as regulators of the plant immune system (NPR1 and NPR3) were demonstrated. The efficacies of several anti-microbial proteins and peptides in enhancement of pathogen resistance were also demonstrated. A pipeline has been established allowing systematic testing of the function of additional candidate genes.