Molecular Characterization of Donacia provosti (Coleoptera: Chrysomelidae) Larval Transcriptome by De Novo Assembly to Discover Genes Associated with Underwater Environmental Adaptations

SIMPLE SUMMARY: Donacia provosti is one of the major pests of aquatic crops. It has been widely distributed in the world causing extensive damage to lotus and rice plants. The larvae generally live-in water; however, little is known about the evolution and molecular mechanisms underlying the adaptation. Here, we generated the first larval transcriptome of D. provosti in order to identify potential genetic mechanisms of aquatic adaptation. About 5036 orthologous clusters were identified among four species and 494 unique clusters were identified from D. provosti larvae including the visual perception. Moreover, 93 orthologous gene pairs were found evolving under positive selection. Our results also showed that 4 gene pairs out of the 93 gene pairs were associated with the “mTOR signaling pathway”, which are predicted to be involved in the molecular mechanism of D. provosti adaptation to the underwater environment. In the light of the increasing availability of transcriptomic information for beetle underwater habitat and evolutionary analyses, it is expected that this paper will provide us with some novel insights into aquatic adaptation in beetles and serves as a foundation for future studies aiming to identify candidate genes underlying the genetic basis of aquatic adaptation in beetles. ABSTRACT: Donacia provosti (Fairmaire, 1885) is a major pest of aquatic crops. It has been widely distributed in the world causing extensive damage to lotus and rice plants. Changes in gene regulation may play an important role in adaptive evolution, particularly during adaptation to feeding and living habits. However, little is known about the evolution and molecular mechanisms underlying the adaptation of D. provosti to its lifestyle and living habits. To address this question, we generated the first larval transcriptome of D. provosti. A total of 20,692 unigenes were annotated from the seven public databases and around 18,536 protein-coding genes have been predicted from the analysis of D. provosti transcriptome. About 5036 orthologous cutlers were identified among four species and 494 unique clusters were identified from D. provosti larvae including the visual perception. Furthermore, to reveal the molecular difference between D. provosti and the Colorado potato beetle Leptinotarsa decemlineata, a comparison between CDS of the two beetles was conducted and 6627 orthologous gene pairs were identified. Based on the ratio of nonsynonymous and synonymous substitutions, 93 orthologous gene pairs were found evolving under positive selection. Interestingly, our results also show that there are 4 orthologous gene pairs of the 93 gene pairs were associated with the “mTOR signaling pathway”, which are predicted to be involved in the molecular mechanism of D. provosti adaptation to the underwater environment. This study will provide us with an important scientific basis for building effective prevention and control system of the aquatic leaf beetle Donacia provosti.