Abstract
We analyze the evolutionary relationships and expression patterns of the large set of genes for chemosensory proteins (CSPs) in the two main pest locusts. We used the available transcriptome and genome data to infer the number of genes using BLAST searches and sequence similarity matrices. Maximum likelihood phylogenies revealed the relationships between these CSPs and CSPs from several arthropods. RNAseq and qPCR allowed associating CSPs to locust phases. Crossing the phylogenetic and expression data allowed us to deduce homologies and conservation of the involvement in the phase change. We confirm that Locusta migratoria has at least 58 CSP gene copies, only five of which lack evidence of expression, and we reveal that Schistocerca gregaria has at least 42 expressed CSP genes. Both species share 21 orthologs, whereas 33 L. migratoria and 15 S. gregaria CSPs seem species-specific. Additional six S. gregaria and four L. migratoria CSPs seem duplications. Although the expression profiles are not especially conserved, seven orthologous CSP pairs share a gregarious over-expression pattern in adult locusts. We thus confirm that the number of locusts’ CSPs is large, due to gene duplications during the evolution of Orthoptera, we establish sequence and potential functional homologies, and we highlight specific CSPs that appear to be involved in locust gregariousness either in general or in a species-specific manner.
Highlights
Locusts recurrently cause important economical losses and lead to famine in some of the most economically depressed areas of the globe
Olfactory sensilla are more abundant in solitarious Schistocerca gregaria individuals than in gregarious ones[34], and injection of solitarious S. gregaria nymphs with corazonin led to gregarization and reduction of the number of antennal sensilla[20]
Analysis of the list of coding sequences (CDS) in L. migratoria’s draft genome[29] reveals 42 possible chemosensory proteins (CSPs) loci located in 30 different scaffolds
Summary
Locusts recurrently cause important economical losses and lead to famine in some of the most economically depressed areas of the globe. We see how combining transcriptome and genome data is useful for a more complete and accurate detection of the set of genes of a protein family, and allows assessing the state of completion of a genome sequencing project (proportion of partially sequenced or unsequenced loci whose expression is confirmed) and might help genome assemblies by relating scaffolds based on their exon content (here we see how scaffold 50720 of L. migratoria’s draft genome version 2.4.1 must be located immediately downstream of scaffold 401450—since LmigCSP1 exons 1 and 2 are in scaffolds 50720 and 401450, respectively).
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