Salim, B. | bioRxiv Science

bioRxiv2026

The genomic basis of heat stress adaptation in indigenous Ethiopian cattle from arid and hot-humid climates

African zebu cattle (Bos indicus) exhibit remarkable adaptation to extreme thermal conditions, yet the genomic bases of this resilience are not fully elucidated. Ethiopia provides a unique natural setting where closely related zebu populations have divergently adapted to hot-arid (DHETZ) and hot-humid (HHETZ) climates. In this study, we performed whole-genome sequencing of 46 Ethiopian zebu cattle from five populations and compared them with Asian zebu, Sudanese zebu, African taurine, and European taurine breeds. By integrating genome-wide SNP analysis, population genetic structure assessment, and multiple selection scans (iHS, Hp, XP-EHH, and XP-CLR), we identified distinct and shared selection signatures between DHETZ and HHETZ cattle. Ethiopian zebu closely clustered with Sudanese zebu but showed clear divergence from Asian zebu and taurine breeds. Although DHETZ and HHETZ cattle exhibited minimal genetic differentiation, reflecting their shared ancestry, each group displayed unique selection signals. DHETZ cattle showed strong selection in genes involved in oxidative stress regulation, protein folding, mitochondrial function, and vascular remodeling (e.g., SESN2, DNAJC8, GRPEL2, ABLIM3, and AFAP1L1). In contrast, HHETZ cattle displayed signatures in genes associated with immune responses, energy metabolism, and angiogenesis inhibition (e.g., MYD88, PRKACA, PRKACB, and WIF1). Several genes, including VEGFC, TNIP3, and DMXL2, were under selection in both groups, suggesting conserved mechanisms of thermotolerance and reproductive adaptation. These findings reveal a dual pattern of genomic adaptation: while core heat-response pathways are shared, population-specific signatures reflect distinct metabolic and vascular strategies for coping with arid versus humid heat stress. This study provides novel insights into the genomic architecture of environmental adaptation in tropical cattle and offers valuable markers for breeding climate-resilient livestock.

genomics↗

bioRxiv2021

Genomic signatures of desert adaptation at gene-rich regions in zebu cattle from the African drylands

Sudan, the largest country in Africa, acts as a corridor between North and sub-Saharan Africa along the river Niles. It comprises warm arid and semi-arid grazing lands, and it is home to the second-largest African population of indigenous livestock. Indigenous Sudanese cattle are mainly indicine/zebu (humped) type. They thrive in the harshest dryland environments characterised by high temperatures, long seasonal dry periods, nutritional shortages, and vector diseases challenges. We investigated genome diversity in six indigenous African zebu breeds sampled in Sudan (Aryashai, Baggara, Butana, Fulani, Gash, and Kenana). We adopted three genomic scan approaches to identify candidate selective sweeps regions (ZHp, FST, XP-EHH). We identified a set of gene-rich selective sweep regions shared across African and Asian zebu or unique to Sudanese zebu. In particular, African and Asian zebu candidate gene-rich regions are detected on chromosomes 2, 5 and 7. They include genes involved in immune response, body size and conformation, and stress response to heat. In addition, a 250 kb selective sweep on chromosome 16 was detected exclusively in five Sudanese zebu populations. This region spans seven genes, including PLCH2, PEX10, PRKCZ and SKI, which are involved in alternative adaptive metabolic strategies of insulin signalling, glucose homeostasis, and fat metabolism. Together, these genes may contribute to the zebu cattle resilience to heat, nutritional and water shortages. Our results highlight the putative importance of selection at gene-rich genome regions, which might be under a common regulatory genetic control, as an evolutionary mechanism for rapid adaptation to the complexity of environmental challenges.

evolutionary biology↗

bioRxiv2020

BoLA-DRB3 gene haplotypes show divergence in native Sudanese cattle from Taurine and Zebu breeds

Autochthonous Sudanese cattle breeds, namely Baggara for beef and Butana and Kenana for dairy, are characterized by their adaptive characteristics and high performance in hot and dry agro-ecosystems, are used largely by nomadic and semi-nomadic pastoralists. Here we analyzed the diversity and genetic structure of the BoLA-DRB3 gene, a genetic locus linked to the immune response, for the indigenous cattle of Sudan and in the context of the global cattle repository. Blood samples (n=225) were taken from three indigenous breeds (Baggara; n=113, Butana; n= 60 and Kenana; n=52) distributed across six regions of Sudan. Nucleotide sequences were genotyped using the sequence-based typing method. Sequence electropherograms were analyzed using the Assign SBT software. We describe 53 alleles, including seven new, novel alleles. In the Baggara breed the number of alleles was 46 (40 previously reported and six new ones), 33 in the Kenana breed (28 previously reported and five new ones), and 33 in the Butana breed (28 previously reported and five new ones). Venn analysis of Sudanese breeds with Southeast Asian, European and American cattle showed 115 alleles of which 14 were unique to Sudanese breeds. Three of the alleles exhibited gene frequency of > 0.5%, representing 26% of the 53 alleles detected in the native Sudanese cattle. Observed versus expected heterozygosity was higher than 0.93 in all three breeds analyzed and equilibrium status revealed by Hardy-Weinberg Equilibrium suggests pure genetic drift. Gene frequency distributions of Baggara cattle showed an even distribution (P = 0.016), consistent with the theoretical proportion expected under balancing selection pressure as opposed to positive or neutral selection. In contrast, Butana and Kenana cattle (P = 0.225 and P = 0.138, respectively) were more congruent with neutral selection, similar to the results obtained for most of the cattle breeds analyzed so far. Sudanese cattle breeds were located within a narrow cloud in an intermediate position between the Zebu and Taurine breeds and close to other Southeast Asian breeds, in accordance with the composite origin of these native breeds, which is also reinforced by the presence of African and Zebu unique BoLA-DRB3 alleles within these breeds. The results of the Principal Component Analysis were in agreement with the overall clustering pattern observed on the NJ and/or UPGMA trees. These results contribute to our understanding of the genetic diversity and distribution pattern of BoLA-DRB3 gene alleles in Sudanese cattle breeds and provide insight into their uniqueness in their ability to survive arrays of tropical diseases and reproduce well in Sudans harsh environment. Author summaryAfrican cattle survive and adapt to a variety of diseases via acquired immunity capable of presenting antigens through the function of the major histocompatibility complex (MHC) or bovine leukocyte antigen (BoLA) in cattle. The aim of this study was to investigate how the immune system is structured and to what extent three economically important breeds in Sudan differ from exotic cattle. Here, we use the sequence-based typing approach to analyze BoLA-DRB3s genetic diversity linked to immunity against complex diseases that infect cattle. By examining 225 indigenous cattle belonging to three breeds in Sudan, we demonstrate that these cattle are unique from all known cattle by identifying seven new alleles; BoLA-DRB3*004:02Sp, BoLA-DRB3*011:02Sp, BoLA-DRB3*018:01Sp, BoLA-DRB3*021:01sp, BoLA-DRB3*024:18Sp, BoLA-DRB3*027:05sp, and BoLA-DRB3*032:01sp. When analyzing frequency of the protein pockets implicated in the antigen-binding function of the MHC complex by PCA we found that pockets 4 and 9 are the ones that best differentiate these native breeds from the rest. This may be attributed to high disease tolerance/susceptibility to tropical infections, such as those carried by ticks and intestinal parasites. Further studies are needed on these newly identified variants and their association with specific common disease(s). This finding is especially important for disease resistance/susceptibility association to help advise on candidate animals in selection schemes.

evolutionary biology↗