Gene expression in diapausing rotifer eggs in response to divergent environmental predictability regimes

Abstract

In unpredictable environments in which reliable cues for predicting environmental variation are lacking, a diversifying bet-hedging strategy for diapause exit is expected to evolve, whereby only a portion of diapausing forms will resume development at the first occurrence of suitable conditions. This study focused on diapause termination in the rotifer Brachionus plicatilis s.s., addressing the transcriptional profile of diapausing eggs from environments differing in the level of predictability and the relationship of such profiles with hatching patterns. RNA-Seq analyses revealed significant differences in gene expression between diapausing eggs produced in the laboratory under combinations of two contrasting selective regimes of environmental fluctuation (predictable vs unpredictable) and two different diapause conditions (passing or not passing through forced diapause). The results showed that the selective regime was more important than the diapause condition in driving differences in the transcriptome profile. Most of the differentially expressed genes were upregulated in the predictable regime and mostly associated with molecular functions involved in embryo morphological development and hatching readiness. This was in concordance with observations of earlier, higher, and more synchronous hatching in diapausing eggs produced under the predictable regime.

Avoiding dead ends: the experimental evolution of constraint as adaptation to environmental variation in Saccharomyces cerevisiae

“…Here, tolerance to extreme events 'hitchhikes' across non-selective events due to the strong association with other vital traits. However, despite an understanding of genetic mechanisms underlying putative bet-hedging traits 21,39,40 themselves, the genetic basis of evolutionary constraints that in uence the persistence of bet-hedging traits has not been studied. The present results suggest that genetic studies of evolved constraints are warranted to better understand the enigma of the persistence of bet hedging over the short-term.…”

Variation in heat shock protein 40 kDa relates to divergence in thermotolerance among cryptic rotifer species

“…An organism’s adaptation to a particular environment or resource availability may occur at the protein level through the regulation of gene expression 45 – 48 . This gene expression regulative mechanism can be observed in situations of rapid environmental changes (i.e., length of growing seasons) in B. plicatilis s.s. 49 , 50 , or in stress response via HSP upregulation 35 , 51 , which is a rapid and often the first response mechanism to environmental perturbation. However, a differential regulatory response among genotypes/species to the same environmental cue (genotype x environment (G x E) variation) has to be encoded somewhere in the genome, typically upstream in gene regulatory elements (e.g., transcription factors, promoters 52 , 53 ).…”