Functional Genomics Investigations of Differential Sensitivity in Related Species
USING NEXT-GENERATION SEQUENCING TO ASSESS MECHANISMS UNDERLYING DIFFERENTIAL SENSITIVITY
The intertidal zone is a highly dynamic environment where species zonate as a consequence of their relative tolerances to abiotic stress. In order to assess regulation of stress responsiveness among intertidal species, I utilized comparative next-generation sequencing to investigate the transcriptomic responses of two, differentially sensitive, intertidal species of porcelain crab (genus Petrolisthes) to natural variability in temperature and pH.
Congeners were exposed to either a low-variability, ambient control or a high-variability stress treatment where temperature spiked +15 °C and pH dropped 0.5 units mimicking natural diel fluctuations. Gill tissue was collected from crabs exposed to a single temperature/pH cycle (naïve response) and from those exposed to several cycles over two-weeks (acclimated response). Among the most strongly differentially expressed genes were those involved in acid-base regulation (e.g. VHAs) and stress recovery (e.g. HSPs), and patterns of expression differed significantly between species in potentially ecologically relevant ways. Although P. manimaculcus exhibited a greater degree of expression change, nearly five times more genes were differentially expressed in P. cinctipes. In addition, for P. manimaculis, expression changes at a given exposure time did not differ significantly between stress and ambient treatments whereas both naïve and acclimated individuals of P. cinctipes showed strong, stress-specific alteration in expression of putative acid-base regulatory genes.
These results suggest that P. manimaculis’ sensitivity to abiotic stress may be a result of a reduced molecular stress response generally, and a limited capacity to alter expression of acid-base regulatory proteins in particular. This reduced responsiveness may be a consistent feature among species susceptible to environmental stress, setting modern habitat limits and potentially acting as a primary determinant of “winners and losers” under future climate change.