Transcriptomic analysis of differentially expressed genes in the oviduct of Rhacophorus omeimontis provides insights into foam nest construction

Abstract

Background The production of foam nests is one of the strategies that has evolved to allow some anuran species to protect their eggs and larvae. Despite considerable knowledge of the biochemical components of and construction behavior leading to anuran foam nests, little is known about the molecular basis of foam nest construction. Rhacophorus omeimontis presents an arboreal foam-nesting strategy during the breeding season. To better understand the molecular mechanism of foam nest production, transcriptome sequencing was performed using the oviduct of female R. omeimontis during the period when foam nest production began and the period when foam nest production was finished. Results The transcriptomes of six oviduct samples of R. omeimontis were obtained using Illumina sequencing. A total of 84,917 unigenes were obtained, and 433 genes (270 upregulated and 163 downregulated) were differentially expressed between the two periods. These differentially expressed genes (DEGs) were mainly enriched in extracellular space and extracellular region based on Gene Ontology (GO) enrichment analysis and in the pathways of two-component system, cell adhesion molecules, steroid hormone biosynthesis and neuroactive ligand-receptor interaction based on Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Specifically, genes encoding lectins, surfactant proteins and immunity components were highly expressed when the foam nest construction began, indicating that the constituents of foam nests in R. omeimontis were likely a mixture of surfactant, lectins and immune defense proteins. During the period when foam nest production was finished, genes related to lipid metabolism, steroid hormone and immune defense were highly expressed, indicating their important roles in regulating the process of foam nesting. Conclusions Our study provides a rich list of potential genes involved in the production of foam nests in R. omeimontis . These results provide insights into the molecular mechanisms underlying the process of foam nest construction and will facilitate further studies of R. omeimontis . Electronic supplementary material The online version of this article (10.1186/s12864-019-5931-7) contains supplementary material, which is available to authorized users.

Form, function, foam: evolutionary ecology of anuran nests and nesting behaviour

“…While the secretions that are whipped into foam are generally derived from egg jelly, their precise physiological and evolutionary origins remain unresolved [68,75]. A recent study by Zhang and colleagues [76] used RNA sequencing to characterize oviduct gene expression changes associated with foam nesting in the Omei treefrog, Rhacophorus omeimontis, providing starting points for the identification of the molecular mechanism of foam production. Additional studies, and in particular comparative work across foam nesting anurans from different families, will provide clues to the evolutionary stepping-stones that lead to foam nesting, address the extent to which independent evolution of foam nesting relies on shared underlying mechanisms, and shed light on the evolutionary feedbacks between behavioural, morphological and physiological adaptations [77].…”

Safety Bubbles: A Review of the Proposed Functions of Froth Nesting among Anuran Amphibians

“…Communal nesting is a cooperative behavioural strategy in which the eggs or egg clutches of multiple mating partners are placed together in the same vicinity or together in direct physical contact. This is in contrast to grouped spawning, where multiple males may join a mating pair to fertilise a single egg clutch [124,125]. Communal nesting is exhibited by anurans that produce frothed [36,80,126] or un-frothed nests [126], whereby nests are laid relatively synchronously and in physical association to form communal masses.…”

Genomic and Transcriptomic Insights into the Genetic Basis of Foam Secretion in Rice Spittlebug Callitettix versicolor

“…The poplar sawfly, Stauronematus compressicornis, uses its salivary gland to excrete foam that can inhibit the feeding of other insects and occupy the food niche [5]. Previous research has predominantly focused on illustrating the function and composition of foams, with little exploration into the genetic basis of foam secretion [6][7][8].…”