Positive Selection Drives the Adaptive Evolution of Mitochondrial Antiviral Signaling (MAVS) Proteins-Mediating Innate Immunity in Mammals

ARIES domains: functional signaling units of type I interferon responses

The innate immune system relies on a network of signaling proteins classified by shared domains, which serve as functional units that orchestrate inflammatory and host defensive activities. Within type I interferon (IFN) responses, the stimulator of interferon genes protein (STING), mitochondrial antiviral-signaling protein (MAVS), Toll-IL-1 receptor-resistance protein domain-containing adapter-inducing interferon-β (TRIF), Toll-like receptor adapter interacting with SLC15A4 on the lysosome (TASL), insulin receptor tyrosine kinase substrate protein of 53 kDa (IRSp53), and GEM interacting protein (GMIP) utilize a conserved pLxIS motif to recruit IRF family transcription factors. Notably, the pLxIS motif functions within a larger signaling unit, which is referred to here as an Activator of Interferon Expression via a pLxIS motif (ARIES) domain. ARIES domains consist of the pLxIS motif and adjacent kinase activation motifs that together drive IFN responses. This review explores how ARIES domains promote immune responses via shared and distinct signaling mechanisms, protein localization, and regulation of metabolic shifts, underscoring their evolutionary conservation and critical role in host defense.

Genomic insights into Yak (Bos grunniens) adaptations for nutrient assimilation in high-altitudes

High-altitude environments present formidable challenges for survival and reproduction, with organisms facing limited oxygen availability and scarce nutrient resources. The yak (Bos grunniens), indigenous to the Tibetan Plateau, has notably adapted to these extreme conditions. This study delves into the genomic basis of the yak's adaptation, focusing on the positive selection acting on genes involved in nutrient assimilation pathways. Employing techniques in comparative genomics and molecular evolutionary analyses, we selected genes in the yak that show signs of positive selection associated with nutrient metabolism, absorption, and transport. Our findings reveal specific genetic adaptations related to nutrient metabolism in harsh climatic conditions. Notably, genes involved in energy metabolism, oxygen transport, and thermoregulation exhibited signs of positive selection, suggesting their crucial role in the yak's successful colonization of high-altitude regions. The study also sheds light on the yak's immune system adaptations, emphasizing genes involved in response to various stresses prevalent at elevated altitudes. Insights into the yak's genomic makeup provide valuable information for understanding the broader implications of high-altitude adaptations in mammalian evolution. They may contribute to efforts in enhancing livestock resilience to environmental challenges.

Patterns of Evolution of TRIM Genes Highlight the Evolutionary Plasticity of Antiviral Effectors in Mammals

The innate immune system of mammals is formed by a complex web of interacting proteins, which together constitute the first barrier of entry for infectious pathogens. Genes from the E3-ubiquitin ligase tripartite motif (TRIM) family have been shown to play an important role in the innate immune system by restricting the activity of different retrovirus species. For example, TRIM5 and TRIM22 have both been associated with HIV restriction and are regarded as crucial parts of the antiretroviral machinery of mammals. Our analyses of positive selection corroborate the great significance of these genes for some groups of mammals. However, we also show that many species lack TRIM5 and TRIM22 altogether. By analyzing a large number of mammalian genomes, here we provide the first comprehensive view of the evolution of these genes in eutherians, showcasing that the pattern of accumulation of TRIM genes has been dissimilar across mammalian orders. Our data suggest that these differences are caused by the evolutionary plasticity of the immune system of eutherians, which have adapted to use different strategies to combat retrovirus infections. Altogether, our results provide insights into the dissimilar evolution of a representative family of restriction factors, highlighting an example of adaptive and idiosyncratic evolution in the innate immune system.

Asymmetric Evolution of Protein Domains in the Leucine-Rich Repeat Receptor-Like Kinase Family of Plant Signaling Proteins

The coding sequences of developmental genes are expected to be deeply conserved, with cis-regulatory change driving the modulation of gene function. In contrast, proteins with roles in defense are expected to evolve rapidly, in molecular arms races with pathogens. However, some gene families include both developmental and defense genes. In these families, does the tempo and mode of evolution differ between genes with divergent functions, despite shared ancestry and structure? The leucine-rich repeat receptor-like kinase (LRR-RLKs) protein family includes members with roles in plant development and defense, thus providing an ideal system for answering this question. LRR-RLKs are receptors that traverse plasma membranes. LRR domains bind extracellular ligands; RLK domains initiate intracellular signaling cascades in response to ligand binding. In LRR-RLKs with roles in defense, LRR domains evolve faster than RLK domains. To determine whether this asymmetry extends to LRR-RLKs that function primarily in development, we assessed evolutionary rates and tested for selection acting on 11 subfamilies of LRR-RLKs, using deeply sampled protein trees. To assess functional evolution, we performed heterologous complementation assays in Arabidopsis thaliana (Arabidopsis). We found that the LRR domains of all tested LRR-RLK proteins evolved faster than their cognate RLK domains. All tested subfamilies of LRR-RLKs had strikingly similar patterns of molecular evolution, despite divergent functions. Heterologous transformation experiments revealed that multiple mechanisms likely contribute to the evolution of LRR-RLK function, including escape from adaptive conflict. Our results indicate specific and distinct evolutionary pressures acting on LRR versus RLK domains, despite diverse organismal roles for LRR-RLK proteins.

Molecular Evolution of the Bactericidal/Permeability-Increasing Protein (BPIFA1) Regulating the Innate Immune Responses in Mammals

Bactericidal/permeability-increasing protein, a primary factor of the innate immune system of mammals, participates in natural immune protection against invading bacteria. BPIFA1 actively contributes to host defense via multiple mechanisms, such as antibacterial, surfactant, airway surface liquid control, and immunomodulatory activities. However, the evolutionary history and selection forces on the BPIFA1 gene in mammals during adaptive evolution are poorly understood. This study examined the BPIFA1 gene of humans compared with that of other mammalian species to estimate the selective pressure derived by adaptive evolution. To assess whether or not positive selection occurred, we employed several different possibility tests (M1 vs. M2 and M7 vs. M8). The proportions of positively selected sites were significant, with a likelihood log value of 93.63 for the BPIFA1 protein. The Selecton server was used on the same dataset to reconfirm positive selection for specific sites by employing the Mechanistic-Empirical Combination model, thus providing additional evidence supporting the findings of positive selection. There was convincing evidence for positive selection signals in the BPIFA1 genes of mammalian species, which was more significant for selection signs and creating signals. We performed probability tests comparing various models based on dN/dS ratios to recognize specific codons under positive selection pressure. We identified positively selected sites in the LBP-BPI domain of BPIFA1 proteins in the mammalian genome, including a lipid-binding domain with a very high degree of selectivity for DPPC. BPIFA1 activates the upper airway's innate immune system in response to numerous genetic signals in the mammalian genome. These findings highlight evolutionary advancements in immunoregulatory effects that play a significant role in the antibacterial and antiviral defenses of mammalian species.

A Simulation Analysis and Screening of Deleterious Nonsynonymous Single Nucleotide Polymorphisms (nsSNPs) in Sheep LEP Gene

Leptin is a polypeptide hormone produced in the adipose tissue and governs many processes in the body. Recently, polymorphisms in the LEP gene revealed a significant change in body weight regulation, energy balance, food intake, and reproductive hormone secretion. This study considers its crucial role in the regulation of the economically important traits of sheep. Several computational tools, including SIFT, Predict SNP2, SNAP2, and PROVEAN, have been used to screen out the deleterious nsSNPs. Following the screening of 11 nsSNPs in the sheep genome, 5 nsSNPs, T86M (C → T), D98N (G → A), N136T (A → C), R142Q (G → A), and P157Q (C → A), were predicted to have a significant deleterious effect on the LEP protein function, leading to phenotypic difference. The analysis of proteins’ stability change due to amino acid substitution using the I-stable, SDM, and DynaMut consistently confirmed that three nsSNPs (T86M (C → T), D98N (G → A), and P157Q (C → A)) increased protein stability. It is suggested that these three nsSNPs may enhance the evolvability of LEP protein, which is vital for the evolutionary adaptation of sheep. Our findings demonstrate that the five nsSNPs reported in this study might be responsible for sheep’s structural and functional modifications of LEP protein. This is the first comprehensive report on the sheep LEP gene. It narrow downs the candidate nsSNPs for in vitro experiments to facilitate the development of reliable molecular markers for associated traits.

Genomic and Computational Analysis of Novel SNPs in TNP1 Gene Promoter Region of Bos indicus Breeding Bulls

Transition nuclear proteins (TNPs), the principal proteins identified in the condensing spermatids chromatin, have been found to play a key role in histone displacement and chromatin condensation during mammalian spermatogenesis. One such gene belonging to the TNP family called TNP1 gene is abundantly expressed in the regulation of spermatogenesis, and its sequence is remarkably well conserved among mammals. Genomic analysis, by sequencing and computational approach, was used to identify the novel polymorphisms and to evaluate the molecular regulation of TNP1 gene expression in Sahiwal cattle breeding bulls. DNA samples were sequenced to identify novel single nucleotide polymorphisms (SNPs) in the TNP1 gene. Modern computational tools were used to predict putative transcription factor binding in the TNP1 promoter and CpG islands in the TNP1 promoter region. In the TNP1 gene, four SNPs, three TATA boxes, and one CAAT box were identified. One CAAT box was discovered at 89 bp upstream of start site ATG. The computational analyses indicated that the polymorphisms inside the promoter sequence results in an added HNF-1 transcription factor binding site. In contrast, the other variations may remove the naturally occurring SRF transcription factor binding site. The CpG islands in the TNP1 promoter region were predicted to be absent by the MethPrimer program before and after SNP site mutations. These findings pave the way for more research into the TNP1 gene's promoter activity and the links between these SNPs and reproductive attributes in the Sahiwal breeding bulls.