SRA

The genome of the white-throated sparrow (Zonotrichia albicollis) contains an inversion polymorphism on chromosome 2 that is linked to predictable variation in a suite of phenotypic traits including plumage color, aggression, and parental behavior. Differences in gene expression between the two color morphs, which represent the two common inversion genotypes (ZAL2/ZAL2 and ZAL2/ZAL2m), are therefore of potential interest toward understanding the molecular underpinnings of these phenotypes. To identify genes that are differentially expressed between the two morphs and correlated with behavior, we quantified both behavior and gene expression in a population of free-living white-throated sparrows. We quantified behavioral responses to simulated territorial intrusions (STIs) early during the breeding season. In the same birds, we then performed a transcriptomewide analysis of gene expression in two behaviorally relevant brain regions, the medial amygdala and hypothalamus. Using network analyses, we identified modules of genes that were correlated with both morph and STI-induced singing behavior. The majority of these genes were located within the inversion, demonstrating the profound effect the inversion has on the expression of genes captured by the rearrangement. Gene pathway analyses revealed that in the medial amygdala, the most prominent pathways were those related to steroid hormone receptor activity. Within these pathways, the only gene encoding such a receptor was ESR1 (estrogen receptor alpha). Our results thus suggest that ESR1 and related genes are important for behavioral differences between the morphs. Overall design: RNA samples from the brain regions HYP and MeA were collected from a total of 19 male white-throated sparrows (10 WS and 9 TS). Free-living birds were collected during the peak of territorial behavior (May-June) the day after a simulated territorial intrusion using mist nets and song playback. For the MeA samples, MeA constituted the majority of the sampled tissue. For the HYP, samples included the caudal portion of the medial preoptic area (POM), the paraventricular nucleus (PVN), the anterior hypothalamus, and the ventromedial hypothalamus (VMH).