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Novel Genes, Ancient Genes, and Gene Co-Option Contributed to the Genetic Basis of the Radula, a Molluscan Innovation
- Source :
- Molecular Biology and Evolution
- Publication Year :
- 2018
-
Abstract
- The radula is the central foraging organ and apomorphy of the Mollusca. However, in contrast to other innovations, including the mollusk shell, genetic underpinnings of radula formation remain virtually unknown. Here, we present the first radula formative tissue transcriptome using the viviparous freshwater snail Tylomelania sarasinorum and compare it to foot tissue and the shell-building mantle of the same species. We combine differential expression, functional enrichment, and phylostratigraphic analyses to identify both specific and shared genetic underpinnings of the three tissues as well as their dominant functions and evolutionary origins. Gene expression of radula formative tissue is very distinct, but nevertheless more similar to mantle than to foot. Generally, the genetic bases of both radula and shell formation were shaped by novel orchestration of preexisting genes and continuous evolution of novel genes. A significantly increased proportion of radula-specific genes originated since the origin of stem-mollusks, indicating that novel genes were especially important for radula evolution. Genes with radula-specific expression in our study are frequently also expressed during the formation of other lophotrochozoan hard structures, like chaetae (hes1, arx), spicules (gbx), and shells of mollusks (gbx, heph) and brachiopods (heph), suggesting gene co-option for hard structure formation. Finally, a Lophotrochozoa-specific chitin synthase with a myosin motor domain (CS-MD), which is expressed during mollusk and brachiopod shell formation, had radula-specific expression in our study. CS-MD potentially facilitated the construction of complex chitinous structures and points at the potential of molecular novelties to promote the evolution of different morphological innovations.
- Subjects :
- 0301 basic medicine
Biology
novelty
Transcriptome
03 medical and health sciences
Chaeta
ddc:570
chitin synthase
Gene expression
Myosin
Genetics
Animals
radula
Mantle (mollusc)
Molecular Biology
Gene
Mollusca
Institut für Biochemie und Biologie
Ecology, Evolution, Behavior and Systematics
Discoveries
Animal Structures
Tylomelania sarasinorum
biology.organism_classification
RNAseq
030104 developmental biology
Evolutionary biology
shell
Subjects
Details
- ISSN :
- 15371719
- Volume :
- 35
- Issue :
- 7
- Database :
- OpenAIRE
- Journal :
- Molecular biology and evolution
- Accession number :
- edsair.doi.dedup.....c0c97daa4dedaaa2422401fd10d98f14