Genomic and transcriptomic insights into molecular basis of sexually dimorphic nuptial spines in Leptobrachium leishanense

Jun Li,Hua Wu,Chao Fu,Fengming Han,Wei Zhang,Haiyan Yu,Wenxia Wang

doi:10.1038/s41467-019-13531-5

Jun Li, Hua Wu + Show 5 more

Open Access

https://doi.org/10.1038/s41467-019-13531-5

Copy DOI

Abstract

Sexually dimorphic (SD) traits are important in sexual selection and species survival, yet the molecular basis remains elusive, especially in amphibians where SD traits have evolved repeatedly. We focus on the Leishan moustache toad (Leptobrachium leishanense), in which males develop nuptial spines on their maxillary skin. Here we report a 3.5 Gb genome assembly with a contig N50 of 1.93 Mb. We find a specific expansion of the intermediate filament gene family including numerous keratin genes. Within these genes, a cluster of duplicated hair keratin genes exhibits male-biased and maxillary skin-specific expression, suggesting a role in developing nuptial spines. We identify a module of coexpressed genes significantly associated with spine formation. In addition, we find several hormones likely to be involved in regulating spine development. This study not only presents a high-quality anuran genome but also provides a reference for studying skin-derived SD traits in amphibians.

Highlights

Dimorphic (SD) traits are important in sexual selection and species survival, yet the molecular basis remains elusive, especially in amphibians where Sexually dimorphic (SD) traits have evolved repeatedly
We found that ME03, representing 170 genes, was significantly correlated with maxillary skin (MS) at stage A in both males and females, suggesting that genes in this module are mainly involved in MS specialization prior to spine development
We detected two recent burst events of transposable elements (TEs) in L. leishanense genome, which is similar to the genomes of R. catesbeiana (5.8 Gb), R. marina (2.6 Gb), and O. pumilio (5.5 Gb) from Neobatrachia

Summary

Introduction

Dimorphic (SD) traits are important in sexual selection and species survival, yet the molecular basis remains elusive, especially in amphibians where SD traits have evolved repeatedly. In anurans (toads and frogs), >90% of the species exhibit larger body sizes in females than in males[9] Another type of SD trait in anurans is skin-derived excrescences, such as the nuptial pads on the digits of hands or on the ventral surfaces of forelimbs[10] and the nuptial spines on the upper jaw[11]. These traits are present mainly in adult males during the breeding period and exhibit a seasonal cycle. It has been proposed that such nuptial spines may be used for male–male combat, stimulation of females, or nest construction/maintenance during the breeding season[25]

Methods

Results

Conclusion