Nuclear progesterone receptor (nPR) is an evolutionary innovation in vertebrates that mediates genomic responses to progesterone. Vertebrates also respond to progesterone via membrane progesterone receptors (mPRs) or membrane associated progesterone receptors (MAPRs) through rapid nongenomic mechanisms. Lampreys are extant agnathan vertebrates, residing at the evolutionary juncture where vertebrates diverged from invertebrates. A survey of the progesterone receptor (PR) gene sequences in lamprey genomes would inform PR gene evolutionary events during the transition from invertebrates to vertebrates. In this study, we annotated sequences of one nPR, four mPR (β, γ, δ and ε) and four MAPR genes from genomes of two lamprey species (Petromyzon marinus and Lethenteron japonicum). To infer the origin and evolutionary history of PR genes, we constructed phylogenetic trees of PR homologous sequences across representative species of metazoans. Phylogenetic analyses revealed that the mPRγ gene first appeared in non-bilaterians, and the mPRβ gene likely arose from a duplication of mPRγ. On the other hand, the mPRγ gene gave rise to the mPRδ and ε genes much later in the vertebrate lineage. In addition, the mPRα gene first appeared in cartilaginous fishes, likely derived from duplication of mPRβ after the agnathan-gnathostome divergence. All known MAPR genes were present in the lamprey genomes. Progesterone receptor membrane component 1 (PGRMC1), neudesin and neuferricin genes probably evolved in parallel in non-bilaterians, whereas two copies of PGRMC genes probably derived from duplication of ancestral PGRMC1 sequence and appeared before the speciation of lampreys. Non-classical mPR and MAPR genes first evolved in non-bilaterians and classical nPR genes evolved later in basal vertebrates. Sequence repertoires for membrane progesterone receptor genes in vertebrates likely originated from an ancestral metazoan sequence and expanded via several duplication events.

Temperature variations significantly influence physiological processes in arthropod. The transient receptor potential (TRP) channels are key cellular sensors in the detection of temperature, pain, and mechanical stimuli. However, a comprehensive genome-wide identification and functional characterization of the TRP gene family in Procambarus clarkii has not yet been conducted. In this study, we performed a genome-wide analysis and identified 29 TRP genes in P. clarkii, including 11 newly reported, which were classified into seven subfamilies: TRPA, TRPC, TRPP, TRPM, TRPML, TRPN, and TRPV. Phylogenetic analysis revealed a remarkable expansion of the TRPA subfamily in crayfish compared with insects. Tissue expression profiling demonstrated diverse transcriptional patterns of PclaTRP genes across different organs. Comparative transcriptome analysis under temperature stress further indicated that P. clarkii employs distinct molecular strategies to cope with thermal extremes: heat stress induces proteostasis disruption and biosynthetic suppression, whereas cold stress promotes controlled metabolic downregulation. Specifically, cold stress (10 °C) significantly modulated the expression of 9 PclaTRP genes (4 genes up-regulated and 5 genes down-regulated), whereas non-noxious (30 °C) and noxious heat (35 °C) challenges drastically affected the mRNA levels of 9 (6 genes up-regulated and 3 genes down-regulated) and 12 (10 genes up-regulated and 2 genes down-regulated) PclaTRP genes, respectively. Moreover, temperature-responsive alternative splicing events were identified in two key thermo-responsive candidate factors, PclaTRPA1 and PclaPain2, implicating them in thermosensation. Together, these findings provide a comprehensive overview of the TRP gene family in P. clarkii, revealing their differential expression patterns and alternative splicing regulation under heat and cold challenges, and identifying candidate genes that warrant further investigation for temperature tolerance improvement in crayfish breeding.

Water temperature fluctuations directly affect the feeding, reproduction, and survival of aquatic animals. Understanding the molecular networks that regulate temperature responses is therefore critical for selective breeding of thermotolerant strains. In this study, we first assessed the thermotolerant performances of two Procambarus clarkii populations (selected and normal cultured populations) with contrasting thermal endurance capacities. Temperature stress challenges showed that the selected population exhibited great endurance capacities to both heat and cold stresses. Further comparative transcriptomic analysis showed that cold stress mainly upregulated energy metabolism genes, whereas heat stress affected oxidative stress and membrane-related genes in both populations. However, we found that immune-related pathway genes were significantly downregulated in the selected population in response to heat challenge. Furthermore, heat shock proteins (HSPs), E3 ubiquitination, and autophagy-related genes showed contrasting expression patterns between the thermotolerant and normal cultured populations, suggesting that transcriptional regulations of these signaling pathways may contribute to thermal tolerance. Collectively, these results provide a reference for breeding thermotolerant P. clarkii strains and supporting the sustainable development of the aquaculture industry.