Study On The Temperature Stress Response Related Genes In The Pacific Oyster

As a characteristic sessile inhabitant of the intertidal zone, the Pacific oyster Crassostrea gigas occupies one of the most physically stressful environments on earth. With high exposure to terrestrial conditions, oysters must tolerate broad fluctuations in temperature range. However, oysters’ cellular and molecular responses to temperature stresses have not been fully characterized.In this study, we analyzed oyster transcriptome data under high and low temperatures. We also identified over 30 key gene candidates, which encoded stress proteins such as heat shock proteins and apoptosis-associated genes that responded to temperature stresses. The characterization of the expression patterns of these genes under short-term cold and hot environments(5°C and 35°C) and long-term cold environments(5°C) were detected by quantitative real-time PCR. The expression of most temperature-responsive genes reached peaks during the recovery stage after heat stress, and these genes were most perturbed around 3 days and responded little to short-term cold stress. In addition, oysters in the second heat challenge after 2 days of recovery showed a milder expression of the temperature-responsive genes and lower mortality rate, which indicated the existence of plasticity in the oyster’s response to heat stress. We confirmed that homeostatic flexibility and anti-apoptosis might be crucial centers of temperature stress responses in oysters. In addition, we analyzed stress protein families in 11 different species and found that the linage-specific expansion of stress genes might be implicated in adaptive evolution. The results indicated that both plasticity and evolution play an important role in the stress-response adaptation of oysters.It has been proposed that the transcription of HSP genes is induced by the release of transcription factor HSF1. We analyzed the DNA sequence that HSF1 bound to by ChIP method and found that besides some HSPs, HSF1 might regulate many genes that involved in various cellular processes.