Abstract
The pre-conditioning of adult marine invertebrates to altered conditions, such as low pH, can significantly impact offspring outcomes, a process which is often referred to as transgenerational plasticity (TGP). This study describes for the first time, the gene expression profiles associated with TGP in the green sea urchin Psammechinus miliaris and evaluates the transcriptional contribution to larval resilience. RNA-Seq was used to determine how the expression profiles of larvae spawned into low pH from pre-acclimated adults differed to those of larvae produced from adults cultured under ambient pH. The main findings demonstrated that adult conditioning to low pH critically pre-loads the embryonic transcriptional pool with antioxidants to prepare the larvae for the “new” conditions. In addition, the classic cellular stress response, measured via the production of heat shock proteins (the heat shock response (HSR)), was separately evaluated. None of the early stage larvae either spawned in low pH (produced from both ambient and pre-acclimated adults) or subjected to a separate heat shock experiment were able to activate the full HSR as measured in adults, but the capacity to mount an HSR increased as development proceeded. This compromised ability clearly contributes to the vulnerability of early stage larvae to acute environmental challenge.
Highlights
To make accurate predictions about the resilience of biodiversity in the future, it is essential to understand the cellular mechanisms that underpin species’ responses to change
The number of annotated transcripts which were up-regulated in the treated samples was highly variable (Table 1), but in general, more transcripts at each time point were up-regulated in the samples where both the adults and the larvae were raised in low pH conditions
The effect was most evident between 2 dpf larvae and adults (Fig. 2). These data clearly highlight the molecular mechanisms underpinning transgenerational plasticity (TGP) in P. miliaris, with maternal pre-loading of transcripts involved in the classical stress response, such as antioxidants and chaperone proteins. We suggest that these transcripts play a protective role in the vulnerable early stage larvae until their own transcriptional responses are fully developed
Summary
To make accurate predictions about the resilience of biodiversity in the future, it is essential to understand the cellular mechanisms that underpin species’ responses to change. In this study we analysed the gene expression profiles of early stage larvae from the green sea urchin Psammechinus miliaris raised under low pH (~1000 μatm) These larvae were produced from either adults raised under ambient conditions (~400 μatm) or pre-acclimated to low pH in IPCC year 2100 conditions (~1000 μatm) to evaluate the cellular level effect of parental conditioning. There was an expectation that larvae produced from adults cultured under ambient conditions and spawned directly into low pH would exhibit the classical stress response to new conditions, namely the heat shock response (HSR) This virtually ubiquitous cellular reaction involves the up-regulation of chaperone proteins, members of the 70 kDa and 90k Da heat shock protein families (Hsp[70] and Hsp[90]). The ability of early stage larvae to mount an HSR was further investigated in a separate experiment where both adults and larvae were subjected to an acute heat shock and the resulting expression levels of nine hsp[70] and hsp[90] genes were evaluated by Q-PCR
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