Transcriptome sequencing and microarray development for the woodrat (Neotoma spp.): custom genetic tools for exploring herbivore ecology

We present the de novo transcriptome sequencing, analysis and microarray development for a vertebrate herbivore, the woodrat (Neotoma spp.). This genus is of ecological and evolutionary interest, especially with respect to ingestion and hepatic metabolism of potentially toxic plant secondary compounds. We generated a liver transcriptome of the desert woodrat (Neotoma lepida) with the Roche 454 platform. The assembled contigs were well annotated using rodent references (99.7% annotation), and biotransformation function was reflected in the gene ontology. The transcriptome was used to develop a custom microarray (eArray, Agilent). To compare the effect of native diet/habitat and phylogenetic similarity, we performed 3 experiments with the Neotoma probes only: one across species with similar habitat niches (N. lepida versus N. bryanti, Palm Springs), one across species with different habitat niches (N. lepida versus N. bryanti, Caspers Wilderness), and one across populations within a species (N. bryant Palm Springs versus Caspers Wilderness). The resulting one-color arrays had high technical and biological quality. Probes designed from the woodrat transcriptome performed significantly better than functionally similar probes from the Norway rat (Rattus norvegicus). Biotransformation processes and functions were highly represented in the results. Comparisons between ecologically similar woodrat species revealed fewer gene expression differences than ecologically different woodrat species. The conspecific comparison had overall fewest differences. Gene expression was compared across 3 groups of woodrats: Neotoma lepida (n=4), N. bryanti Palm Springs (n=4), and N. bryanti Caspers Wilderness (n=4). Animals were fed a rabbit chow diet, called control; intake was monitored over 10 days, after which RNA was extracted from hepatic tissue. One-color arrays were performed.