GSE126674
Worker antennal gene expression in Solenopsis invicta identifies candidate genes for queen discrimination (Nugen_lib_RNA-seq-2)
Queen discrimination behavior in the red imported fire ant Solenopsis invicta maintains its two types of societies: colonies with one (monogyne) or many (polygyne) queens, yet the underlying genetic mechanism is poorly understood. This behavior is controlled by two supergene alleles, SB and Sb, with ~600 genes. Polygyne workers, having either the SB/SB or SB/Sb genotype, accept additional SB/Sb queens into their colonies but kill SB/SB queens. While monogyne workers, all SB/SB, reject all additional queens regardless of genotype. Because the SB and Sb alleles do not recombine, it is difficult to determine which genes within the supergene mediate this differential worker behavior. We hypothesized that the alternate worker genotypes sense queens differently because of different patterns of gene expression in their main sensory organ, the antennae. To identify such differentially expressed genes, we sequenced RNA from four biological replicates of pooled antennae from three groups of workers: monogyne SB/SB, polygyne SB/SB, and polygyne SB/Sb. We identified 81 differentially expressed protein coding genes with 14 encoding potential odor metabolism and perception proteins. We focused on the two differentially expressed odorant perception genes: an odorant binding protein SiOBP12 and an odorant receptor SiOR463. We found that the SiOR463 was lost in the Sb-genome. In contrast, the SiOBP12 has an Sb-specific duplication SiOBP12b', which was expressed in the SB/Sb worker antennae, while both paralogs SiOBP12 and SiOBP12b' were expressed in the body. This result indicates that SiOBP12b' has gained an antennal promoter or enhancer and suggests neofunctionalization, perhaps for queen discrimination behavior. Overall design: Extracted total mRNA of antennae of three worker types: monogyne SB/SB, polygyne SB/SB and polygyne SB/Sb. Four biorelicates were conducted (total 12 samples). RNA samples were amplified using Nugen Ovation v.2 kit independently (12 samples). Four samples of the same genotype were mixed to make one representative sample for sequencing on the Illumina HiSeq platform with a 150 paired-end protocol.