Molecular Mechanisms Of High And Low Temperature Tolerance In Ruditapes Philippinarum Revealed By Comparative Transcriptomic Analysis

Increasing temperature is causing rapid changes in oceanic environments.However,understanding the responses of marine mollusk and shellfish to such environmental changes remain a major challenge,yet it is key to predicting future biodiversity loss or gain.In this study,molecular mechanisms of adaptation to acute temperature change were investigated in low and high latitude populations of the Manila clam Ruditapes philippinarum,and temperatureresponsive genes and pathways were identified under acute temperature stress(-1℃ and 28℃).A weighted gene co-expression network analysis(WGCNA)and gene family analysis of HSP70,HSP90 and HSF was also carried out using RNA-seq data from gill transcriptome in response to high and low temperature stress.Transcriptome analysis revealed an extensive set of genes and pathways responding to acute temperature stress.Physiological changes at the molecular level were compared to explore the potential differences in the clam’s response and adaptation to temperature change,and to uncover the underlying mechanisms of resilience or sensitivity to stress conditions in the two clam populations.The enrichment of genes involved in protein processing in endoplasmic reticulum was integral to the adaptation of the clams to stressful conditions.Furthermore,upregulation of phagosome-related genes and pathway were significantly enriched under acute high temperatures.Interestingly,the upregulation of xenobiotic metabolism by cytochrome P450 showed population-specific response in the low-latitude clams under both heat and cold stress but not in the high-latitude clams,whereas genes encoding peroxisomes were upregulated in high-latitude clams under heat stress but not in low-latitude clams.83 RpHSP70,6 RpHSP90 and 3 RpHSF genes were identified in R.philippinarum.The structural characteristics,chromosomal localization,and the gene structure map was constructed to reveal the characteristics of protein structures.Furthermore,the expression profiling of transcriptome data showed the expression pattern of HSP70,HSP90 and HSF genes in Manila clam from different population and under high and low temperature stress.In addition,proteinprotein interaction network analysis was performed between HSP70,HSP90 and HSF gene family which enabled us to recognize the regulatory relationship between two HSP gene families and HSF gene family.Furthermore,the predicted sub-cellular location revealed a diversified subcellular distribution of HSP70,HSP90 and HSF proteins which may be directly or indirectly associated with functional diversification under heat stress condition.This study provided useful information related to the response of R.philippinarum to temperature stress,which could be helpful for improving the temperature stress resistance of these clams in the aquaculture industry,as well as improving our understanding to enable the prediction of future biodiversity trends under temperature change scenarios.On the other hand,a total 32 gene modules were identified,of which 18 gene modules were identified as temperature-related modules.Blue module was one significantly correlated with temperature which was associated with the cellular metabolism,apoptosis pathway,ER stress and othersOur overall study provided new insight into molecular response of Manila clam to high and low temperature stress.Species like Manila clam which are widely distributed in the sea may respond differentially to temperature stress,especially habitat-specific responses.This study devoted to address this gap by assessing temperature stress response to Manila clam fromlow andhighlatitudepopulationsanddelineatingtheir potential thermalacclimationandadaption.