Abstract
BackgroundColor vision and phototactic behavior based on opsins are important for the fitness of insects because of their roles in foraging and mate choice. Related topics, including the duplication and loss of opsin genes, have been well investigated in insect orders such as Coleoptera, Lepidoptera, Hymenoptera, Odonata and Orthoptera, and the findings have been used to develop pest management strategies involving light trapping. Mirid bugs of Hemiptera, which are pests that cause heavy economic losses, show capacity for color discrimination and phototaxis. However, the opsins in mirid bugs remain uncharacterized. Herein, we examined five species to investigate the evolution of opsins in the family Miridae.ResultsUsing RNA-seq, we identified several contigs showing high identity with opsins, including four contigs in Apolygus lucorum and three contigs each in Adelphocoris suturalis, Adelphocoris fasciaticollis, Adelphocoris lineolatus and Nesidiocoris tenuis. Phylogenetic analyses indicated that one of these genes clustered with ultraviolet-sensitive (UV) opsins and that the others clustered with long-wavelength (LW) opsins, suggesting that duplication of LW opsins and loss of blue light-sensitive (B) opsins occurred in mirid bugs. The existence of introns in the LW opsins of mirid bugs suggested that the duplication events were DNA based. Both LW1 and LW2 opsins of mirid bugs were found to be under strong purifying selection. The LW1 opsins were significantly more highly expressed than the LW2 and UV opsins.ConclusionsWe identified the opsins of mirid bugs using five selected mirid species as a representative sample. Phylogenetic analyses clustered one of the genes with UV opsins and the others with LW opsins, suggesting the occurrence of LW opsin duplication and B opsin loss during the evolution of mirid bugs. Intron detection suggested that the identified duplication event was DNA based. The evidence of strong purifying selection and the relatively high expression levels suggested that these opsins exhibit fundamental functions in mirid bugs.
Highlights
Color vision and phototactic behavior based on opsins are important for the fitness of insects because of their roles in foraging and mate choice
Xu et al BMC Ecol Evo (2021) 21:66 groups: phytozoophages and zoophytophages [2,3,4,5]
Through RNA-seq and phylogenetic analyses, we found that the LW and UV opsins of mirid bugs clustered with the opsins of other insects; no mirid opsins clustered with the B opsins, suggesting that B opsins have been lost in mirid bugs, similar to the situation in coleopteran insects [25,26,27]
Summary
Color vision and phototactic behavior based on opsins are important for the fitness of insects because of their roles in foraging and mate choice. Several mirid bugs (e.g., Ap. lucorum, Ad. suturalis) have attracted much attention because they feed on more than 100 plant species and cause significant economic losses [4,5,6,7]. Given their color vision and positively phototactic behavior, color and light traps are used to monitor and manage these nocturnal pests [8,9,10]. The details of opsin evolution in mirid bugs remains unclear
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