RNA-seq coupled to proteomic analysis reveals high sperm proteome variation between two closely related marine mussel species

Abstract

Model systems for the study of fertilization include marine invertebrates with external fertilisation, such as abalones, sea urchins and mussels, because of the ease with which large quantities of gametes released into seawater can be collected after induced spawning. Unlike abalones and sea urchins, hybridisation has been reported between mussels of different Mytilus spp., which thus makes them very appealing for the study of reproductive isolation at both pre- and postzygotic levels. There is a lack of empirical proteomic studies on sperm samples comparing different Mytilus species, which could help to advance this study. A comparative analysis of sperm proteomes across different taxa may provide important insights into the fundamental molecular processes and mechanisms involved in reproductive isolation. It might also contribute to a better understanding of sperm function and of the adaptive evolution of sperm proteins in different taxa. There is now growing evidence from genomics studies that multiple protein complexes and many individual proteins might have important functions in sperm biology and the fertilisation process. From an applied perspective, the identification of sperm-specific proteins could also contribute to the improved understanding of fertility problems and as targets for fertility control.

RNA-seq data from mature male gonads of marine mussels Mytilus edulis and M. galloprovincialis

“…2a in Ref. [1] ). An enrichment analysis (Fisher׳s exact test) was carried out for those loci that showed significant differences (at least in one isotig within locus) between samples of the two Mytilus spp.…”

“…One piece of gonad tissue was immediately snap frozen, labelled and preserved long-term in liquid nitrogen prior to further RNA-seq analysis. A second piece was used to carry out a histological test (based on standard hematoxylin-eosin stain) to assess the sex and stage of gonad maturity as explained in Romero et al [1] . This procedure was repeated for mussels from both species until samples from 6 individual mussels from each Mytilus species were obtained corresponding to mature male individuals for further RNA-seq analysis.…”

“… Because these two marine mussel species are able to hybridise where their distribution overlap some of the differential expressed genes could be good targets for further evolutionary studies in relation to the study of reproductive isolation mechanisms that ultimately could lead to speciation ( e.g. see Romero et al [1] ). The present transcriptome database, once is translated to protein sequences, can be further used for tissue and organism-specific proteomic analysis in order to enhance the number and quality of protein identifications through mass spectrometry analysis ( e.g.…”

“… The present transcriptome database, once is translated to protein sequences, can be further used for tissue and organism-specific proteomic analysis in order to enhance the number and quality of protein identifications through mass spectrometry analysis ( e.g. see Romero et al [1] ). …”

“…Because these two marine mussel species are able to hybridise where their distribution overlap some of the differential expressed genes could be good targets for further evolutionary studies in relation to the study of reproductive isolation mechanisms that ultimately could lead to speciation ( e.g. see Romero et al [1] ).…”