👤 Daniela Lourenco

Tick infestation is one of the main challenges in tropical beef cattle production, leading to significant economic losses. Knowledge of the molecular factors underlying natural tick resistance in cattle contributes to genetic selection through the identification of biomarkers that can be used to accurately identify animals resistant to ticks. Although several genes associated with resistance to ticks have been identified, the molecular mechanisms underlying tick resistance are yet to be elucidated. This study investigated the biological processes, pathways, and key proteins involved in the resistance to the tick Rhipicephalus (Boophilus) microplus in a tropically adapted beef cattle breed. Tick resistance was evaluated in 162 Caracu cows. Blood samples were collected from a subset of 16 extreme animals, including eight with a high tick load (SUS) and eight with a low tick load (RES), for proteomic analysis by LC-MS/MS. A total of 172 and 34 proteins were exclusively identified in plasma samples from the SUS and RES groups, respectively. In addition, 14,034 proteins were detected in the blood plasma of both groups, of which 51 and 101 proteins were significantly increased in plasma samples of the SUS and RES groups, respectively. Among the top 20 proteins with the highest absolute log-fold change values, those encoded by the RNASE1, TNS2, NOXO1, ZNRF3, APOA4, KMT2B, RPS6KA5, PON1, C4BPA, SETD2, HP, TMEM63A, MAST2, and SETD1B genes were highlighted based on their functions that may contribute to a response to tick infestation. Functional enrichment analysis revealed 36 biological processes, 35 molecular functions, and 16 pathways to be significant (P < 0.05), highlighting those related to hemostasis, vesicular transport, cell proliferation and migration, calcium, actin, lipids, scavenger receptors, hydrogen peroxide, tyrosine, and insulin-like growth factor, which may contribute to tick resistance. In addition, PPI network analysis revealed several proteins involved in complement and coagulation systems, hematopoiesis, and immune response as important nodes, based on their centrality and edges. The identification of differentially abundant proteins between RES and SUS animals, as well as their relationships and roles in key biological processes and molecular pathways detected, contribute to improving our understanding of the mechanisms underlying tick resistance in naturally adapted cattle breeds. Furthermore, the differentially abundant proteins detected in this study are potential biomarkers for the response to R. microplus infestation. Show less

Heat stress has deleterious effects on physiological and performance traits in livestock. Within this context, using tropically adapted cattle breeds in pure herds or terminal crossbreeding schemes to explore heterosis is attractive for increasing animal production in warmer climate regions. This study aimed to identify biological processes, pathways, and potential biomarkers related to thermotolerance in Caracu, a tropically adapted beef cattle breed, by proteomic analysis of blood plasma. To achieve this goal, 61 bulls had their thermotolerance evaluated through a heat tolerance index. A subset of 14 extreme animals, including the seven most thermotolerant (HIGH group) and the seven least thermotolerant (LOW group), had their blood plasma samples used for proteomic analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The differentially regulated proteins detected between HIGH and LOW groups were used to perform functional enrichment analysis and a protein-protein interaction network analysis. A total of 217 proteins were detected only in the HIGH thermotolerant group and 51 only in the LOW thermotolerant group. In addition, 81 and 87 proteins had significantly higher and lower abundancies in the HIGH group, respectively. Regarding proteins with the highest absolute log-fold change values, we highlighted those encoded by DUSP5, IGFALS, ROCK2, RTN4, IRAG1, and NNT genes based on their functions. The functional enrichment analysis detected several biological processes, molecular functions, and pathways related to cellular responses to stress, immune system, complement system, and hemostasis in both HIGH and LOW groups, in addition to terms and pathways related to lipids and calcium only in the HIGH group. Protein-protein interaction (PPI) network revealed as important nodes many proteins with roles in response to stress, hemostasis, immune system, inflammation, and homeostasis. Additionally, proteins with high absolute log-fold change values and proteins detected as essential nodes by PPI analysis highlighted herein are potential biomarkers for thermotolerance, such as ADRA1A, APOA1, APOB, APOC3, C4BPA, CAT, CFB, CFH, CLU, CXADR, DNAJB1, DNAJC13, DUSP5, FGA, FGB, FGG, HBA, HBB, HP, HSPD1, IGFALS, IRAG1, KNG1, NNT, OSGIN1, PROC, PROS1, ROCK2, RTN4, RYR1, TGFB2, VLDLR, VTN, and VWF. Identifying potential biomarkers, molecular mechanisms and pathways that act in response to heat stress in tropically adapted beef cattle contributes to developing strategies to improve performance and welfare traits in livestock under tropical climates. Show less

The purpose of this study was to identify genomic regions associated with carcass traits in an experimental Nelore cattle population. The studied data set contained 2,306 ultrasound records for longissimus muscle area (LMA), 1,832 for backfat thickness (BF), and 1,830 for rump fat thickness (RF). A high-density SNP panel (BovineHD BeadChip assay 700k, Illumina Inc., San Diego, CA) was used for genotyping. After genomic data quality control, 437,197 SNPs from 761 animals were available, of which 721 had phenotypes for LMA, 669 for BF, and 718 for RF. The SNP solutions were estimated using a single-step genomic BLUP approach (ssGWAS), which calculated the variance for windows of 50 consecutive SNPs and the regions that accounted for more than 0.5% of the additive genetic variance were used to search for candidate genes. The results indicated that 12, 18, and 15 different windows were associated to LMA, BF, and RF, respectively. Confirming the polygenic nature of the studied traits, 43, 65, and 53 genes were found in those associated windows, respectively for LMA, BF, and RF. Among the candidate genes, some of them, which already had their functions associated with the expression of energy metabolism, were found associated with fat deposition in this study. In addition, ALKBH3 and HSD17B12 genes, which are related in fibroblast death and metabolism of steroids, were found associated with LMA. The results presented here should help to better understand the genetic and physiologic mechanism regulating the muscle tissue deposition and subcutaneous fat cover expression of Zebu animals. The identification of candidate genes should contribute for Zebu breeding programs in order to consider carcass traits as selection criteria in their genetic evaluation. Show less