Abstract
Abstract
Background Opsin is an important molecular basis of the visual system, besides, it was discovered that opsins have also evolved additional functions despite color vision. However, the study of the unconventional function has been limited to a few species. With the increasing number of genome databases, various numbers and types of opsins have been identified in insects due to gene duplications or losses. The brown planthopper (Nilaparvata lugens, BPH) is a Hemipteran rice pest known for its long-distance migration capability. Opsins in BPH were identified and characterized by analyzing the genome and transcriptome. RNA interference (RNAi) was used to investigate the functions of opsins, and the potential molecular mechanism was studied by the Illumina Novaseq 6000 platform-based transcriptome sequencing.Results Four opsins belonging to G protein-coupled receptors were identified in BPH genome, including one long-sensitive opsin (Nllw) and three ultraviolet-sensitive opsins (NlUV1-3). A tandem array of NlUV1/2 on chromosome suggested a gene duplication event, with similar exons distribution. Spatiotemporal expression modes showed that the four opsins were highly expressed in eye with age-different expression levels, indicating functional differentiation. RNAi targeting each of the four opsins did not significantly affect the survival of BPH in phytotron, but silencing of Nllw resulted in melanism of the body color. Further transcriptome analysis revealed up-regulation of a tyrosine hydroxylase gene (NlTH) and down-regulation of an arylalkylamine-N-acetyltransferases gene (NlaaNAT) in BPH, indicating that Nllw is involved in body color plastic development through the tyrosine-mediated melanism pathway.Conclusions This study provides the first evidence in a Hemipteran insect that an opsin (Nllw) takes part in the regulation of cuticle melanization, confirming the visual system cross-talks with the morphological differentiation in insects.
Publisher
Research Square Platform LLC