1a. Objectives (from AD-416):
1. Perform large-scale EST study to significantly increase the breadth and depth of transcriptome coverage of the fire ant Solenopsis invicta using 454 pyrosequencing technology. 2. Develop an oligo microarray for fire ants for gene expression studies using all available EST sequence data (including new data from objective 1). 3. Develop a custom assay for screening SNPs for linkage and population genomic studies of fire ants.
1b. Approach (from AD-416):
DNA sequence data will be generated for the transcriptome of S. invicta by sequencing three normalized cDNA libraries using 454 pyrosequencing technology. All resulting sequences will be run through an automatic pipeline to assemble and preliminarily annotate the sequences. Microarray development will occur in two phases. First, a pilot array will be constructed to identify the best probes for the unigenes identified from the sequencing efforts (244K feature microarray). The best performing probes (and correct orientation) for each sequence then will be synthesized along with positive and negative controls on a 4 X 44K feature microarray, which will be the platform used for subsequent studies. This array will be utilized for four experiments focusing on innate immunity, reproductive physiology, and social organization (including studies of Gp-9, a single gene associated with social organization in this ant). Array probes, layout, and purchase information will be made publicly available on an updated version of a fire ant database. Intraspecific SNPs will be identified using pipeline filtering methods developed for this purpose. A SNP panel consisting of 1536 SNPs will be developed and utilized to construct a moderately dense linkage map, to identify genes linked to Gp-9, to determine whether gametic disequilibrium between Gp-9, SNPs and co-expressed genes exists, and to determine whether these candidate genes are consistently associated with social form as has been shown for Gp-9. Finally, a web-based platform integrating these data in an easily accessible format will be developed.
3. Progress Report:
This project is related to Objective 1 of this in-house project: Develop functional genomic resources and employ these resources to examine the genetic basis of biological traits that can potentially be used for biologically based control, including implications for the geographic origins of infestations. The goal of this project is to develop new functional genomic resources for fire ants. A new microarray that includes every potentially transcribed gene region in fire ants was developed and utilized for a study comparing gene expression differences between queens that either initiated colony founding independently or in the presence of additional queens. Microarray analyses revealed numerous differentially expressed genes. These genes represent important candidate genes for fire ant social behavior (e.g., social genes). An additional gene expression study comparing expression profiles of foraging workers versus nurse workers also was completed. The results of this project are summarized in a manuscript in preparation. Necessary samples for two such comparative gene expression studies have collected and archived.