Heat Shock Protein Expression is Upregulated after Acute Heat Exposure in Three Species of Australian Desert Birds

Abstract

Desert birds must cope with occasional and unpredictable heat waves, which are slowly becoming more frequent with climate change. Different orders of birds have different physiological and behavioural capacities that may aid survival during a heat wave. To date, the expression of genes related to heat exposure have not been studied across different bird orders. We hypothesised that acutely exposing native Australian birds whose natural habitat include arid environments to a high temperature (45 °C), similar to during a heat wave, would result in the upregulation of genes with protective effects against cell damage (BCL-2, VEGFA and heat shock proteins) and inflammation (interleukins), as well as the downregulation of genes involved in the coagulation pathway (fibrinogen). We used eight each of captive-bred Budgerigars (Melopsittacus undulatus), Zebra Finches (Taeniopygia guttata) and Diamond Doves (Geopelia cuneata). Four birds of each species were exposed to a temperature that was within the zone of thermal neutrality (35 °C), while the other four birds were exposed to a higher temperature (45 °C). The mRNA expression of selected genes were then measured using high-throughput qPCR platform (Fluidigm®, BioMark™). The results supported the hypothesis that acute exposure to a high temperature would result in the upregulation of heat shock protein (HSP) genes, but there was no significant upregulation of other genes with protective effects against cell damage nor genes associated with inflammation. The results also do not support the hypothesis that acute heat exposure would result in downregulation of the genes involved in the coagulation pathway in these birds. Among all the tissues that were analysed, the gastrointestinal tissue had the highest number of upregulated HSP genes, possibly indicating that this tissue requires the most protection to continue functioning. Diamond Dove organs also had the highest number of HSP genes upregulated, possibly a reflection of their ability to better protect their cells at high temperatures.