Genome-wide association study reveals the underlying regulatory mechanisms of red blood traits in Anadara granosa.

BACKGROUND: Anadara granosa, commonly known as the blood clam, exhibits the unusual characteristic of having red blood among invertebrates. There is significant individual variation in blood color intensity among blood clams; individuals with vibrant red blood are deemed healthier and exhibit stronger stress resistance. However, the molecular basis underlying these red blood traits (RBTs) remains poorly understood. RESULTS: In this study, we performed genome-wide association studies (GWAS) in a population of 300 A. granosa individuals, focusing on RBTs as measured by hemoglobin concentration (HC), total hemocyte count (THC), and heme concentration (HEME). Our analysis identified 18 single nucleotide polymorphisms (SNPs) correlated with RBTs, subsequently selected 117 candidate genes within a 100 kb flanking region of these SNPs, potentially involved in the RBTs of A. granosa. Moreover, we discovered two haplotype blocks specifically associated with THC and HEME. Further analysis revealed eight genes (Septin7, Hox5, Cbfa2t3, Avpr1b, Hhex, Eif2ak3, Glrk, and Rpl35a) that significantly influence RBTs. Notably, a heterozygous A/T mutation in the 3'UTR of Cbfa2t3 was found to promote blood cell proliferation. These genes suggest that the hematopoietic function plays a significant role in the variability of RBTs in A. granosa. CONCLUSIONS: Our findings reveal a conservation of the regulatory mechanisms of RBTs between blood clams and vertebrates. The results not only provide a scientific basis for selective breeding in blood clams, but also offer deeper insights into the evolutionary mechanisms of RBTs in invertebrates.

Transcriptomic analysis of mRNA and miRNA reveals new insights into the regulatory mechanisms of Anadara granosa responses to heat stress.

Temperature fluctuations resulting from climate change and global warming pose significant threats to various species. The blood clam, Anadara granosa, a commercially important marine bivalve, predominantly inhabits intertidal mudflats that are especially susceptible to elevated temperatures. This vulnerability has led to noticeable declines in the survival rates of A. granosa larvae, accompanied by an increase in malformations. Despite these observable trends, there is a lack of comprehensive research on the regulatory mechanisms underlying A. granosa's responses to heat stress. In this study, we examined the survival rates of A. granosa under varying high temperature conditions, selecting 34 °C as heat stress temperature. Enzyme activity assays have shed light on A. granosa's adaptive response to heat stress, revealing its ability to maintain redox balance and transition from aerobic to anaerobic metabolic pathways. Subsequently, mRNA and miRNA transcriptome analyses were conducted, elucidating several key responses of A. granosa to heat stress. These responses include the upregulation of transcription and protein synthesis, downregulation of proteasome activity, and metabolic pattern adjustments. Furthermore, we identified miRNA-mRNA networks implicated in heat stress responses, potentially serving as valuable candidate markers for A. granosa's heat stress response. Notably, we validated the involvement of agr-miR-3199 in A. granosa's heat stress response through its regulation of the target gene Foxj1. These findings not only deepen our understanding of the molecular mechanisms underlying the blood clam's response to heat stress but also offer valuable insights for enhancing heat stress resilience in the blood clam aquaculture industry. Moreover, they contribute to improved cultivation strategies for molluscs in the face of global warming and have significant implications for the conservation of marine resources and the preservation of ecological balance.