De novo characterization of the transcriptome of color-polymorphic spider Gasteracantha cancriformis, with special reference to pigment genes
Animal coloration is a complex trait useful for studying adaptive evolution. In consequence, a major goal in evolutionary biology is to understand the genetic and developmental basis underlying coloration in animals and thus establish direct links between genetic and phenotype variability. Genomics tools have contributed to identifying the specific genes and variants responsible for color variation in non-model animals, but the evidence is specially biased towards some taxa while groups such as arachnids have been neglected. In this study we seek to identify genes that underlie the production of different colors in spiders and generate genomic resources for these organisms. By deep sequencing RNA-seq libraries from yellow, orange, white and black females of the color polymorphic spider Gasteracantha cancriformis we generated the first assembled transcriptome for this species and identified genes that were differentially expressed between color morphs. Among these, we detected genes with known roles in pigmentation pathways for carotenoids, melanin, ommochromes, and pteridines, suggesting that abdominal coloration in spiders likely involve both pigmentary and structural coloration. Signatures of positive selection on these genes suggests that abdominal coloration in G. cancriformis could play an adaptive role in this species, still unknown. However, the fact of us identifying more venom glands genes expressed in the most conspicuous morphs we tested (i.e., yellow and orange), is suggestive of color pattern likely serving a defensive function against predators in these spiders. Overall, our results provide evidence that several pathways known to control pigmentation in insects and vertebrates also play a role in arachnids.
Animal coloration is a complex trait useful for studying adaptive evolution. In consequence, a major goal in evolutionary biology is to understand the genetic and developmental basis underlying coloration in animals and thus establish direct links between genetic and phenotype variability. Genomics tools have contributed to identifying the specific genes and variants responsible for color variation in non-model animals, but the evidence is specially biased towards some taxa while groups such as arachnids have been neglected. In this study we seek to identify genes that underlie the production of different colors in spiders and generate genomic resources for these organisms. By deep sequencing RNA-seq libraries from yellow, orange, white and black females of the color polymorphic spider Gasteracantha cancriformis we generated the first assembled transcriptome for this species and identified genes that were differentially expressed between color morphs. Among these, we detected genes with known roles in pigmentation pathways for carotenoids, melanin, ommochromes, and pteridines, suggesting that abdominal coloration in spiders likely involve both pigmentary and structural coloration. Signatures of positive selection on these genes suggests that abdominal coloration in G. cancriformis could play an adaptive role in this species, still unknown. However, the fact of us identifying more venom glands genes expressed in the most conspicuous morphs we tested (i.e., yellow and orange), is suggestive of color pattern likely serving a defensive function against predators in these spiders. Overall, our results provide evidence that several pathways known to control pigmentation in insects and vertebrates also play a role in arachnids.
Universidad del Rosario