Diapause vs. reproductive programs: transcriptional phenotypes in a keystone copepod

Many arthropods undergo a seasonal dormancy termed diapause to optimize timing of reproduction in highly seasonal environments. In the North Atlantic, the copepod Calanus finmarchicus completes one to three generations annually with some individuals maturing into adults, while others interrupt their development to enter diapause. It is unknown which, why and when individuals enter the diapause program. Transcriptomic data from copepods on known programs were analyzed using dimensionality reduction of gene expression and functional analyses to identify program-specific genes and biological processes. These analyses elucidated physiological differences and established protocols that distinguish between programs. Differences in gene expression were associated with maturation of individuals on the reproductive program, while those on the diapause program showed little change over time. Only two of six filters effectively separated copepods by developmental program. The first one included all genes annotated to RNA metabolism and this was confirmed using differential gene expression analysis. The second filter identified 54 differentially expressed genes that were consistently up-regulated in individuals on the diapause program in comparison with those on the reproductive program. Annotated to oogenesis, RNA metabolism and fatty acid biosynthesis, these genes are both indicators for diapause preparation and good candidates for functional studies. Lenz, Roncalli and colleagues examine the difference in transcriptional phenotype in Calanus finmarchicus during reproductive and dormant phases. Their findings indicate gene targets for assessment of reproductive strategies in this high latitude copepod crucial to marine food webs.

Automated summary

The study analyzed gene expression differences in copepods during different reproductive processes, identifying indicators for diapause preparation and potential genes for functional studies. Through transcriptomic data and functional analysis, physiological differences in copepods during different reproductive and dormant phases were revealed.