Nuclear genome-encoded mitochondrial OXPHOS complex I genes in Buffalo show tissue-specific differences

Abstract

Abstract Background Buffaloes' energy status is a vital attribute influencing their phenotypic traits and overall health. Mitochondria, primarily through oxidative phosphorylation (OXPHOS), contribute significantly to energy generation; both nuclear (nDNA) and mitochondrial (mtDNA) genomes are involved in OXPHOS process. Previous studies from our laboratory have reported tissue heterogeneity in buffaloes, particularly in mitochondrial functional attributes, is influenced by the mtDNA. Furthermore, there is evidence of higher OXPHOS complex I activity and expression of OXPHOS complex I genes encoded by the mtDNA in various buffalo tissues. Complex I is the largest and mostly involved in energy generation and maintenance of reactive oxygen species. This largest OXPHOS complex consists of proteins encoded by both nDNA and mtDNA. Currently, the tissue-specific expression of nDNA encoded OXPHOS complex I genes expression in metabolically active tissues of buffalo are not well understood. Therefore, the study aimed to investigate the tissue-specific expression of nDNA-encoded OXPHOS complex I genes in buffaloes. Methods and Results To analyze the expression of the OXPHOS complex I genes encoded by nDNA across the various tissues to gain insight into tissue-specific diversity in energy metabolism, RNA-Seq was performed on total RNA extracted from kidney, heart, brain, and ovary of four buffaloes, subsequently identified differentially expressed genes (DEGs) in various tissues comparison. Out of 57 identified OXPHOS complex I genes encoded by nDNA, 51 genes were found to be expressed in each tissue. Comparative analysis revealed 12 DEGs between kidney and brain, 30 for kidney vs ovary, 26 for kidney vs heart, 20 for heart vs brain, 38 for heart vs ovary, and 26 for brain vs ovary, with log2(FC)≥1 and p<0.05. Notably, compared to the ovary, other tissues such as the heart, kidney cortex, and brain exhibited a higher proportion of up-regulated OXPHOS complex I genes. The finding of nuclear derived OXPHOS complex I genes expression of our study showed a close relation with our earlier published report from our laboratory concerning OXPHOS complex I activity. Conclusions Our findings revealed substantial changes in OXPHOS complex I subunit gene expression encoded by nDNA across tissues, with up-regulation of specific genes potentially reflecting increased metabolic needs or adaptation to specific roles. These tissue-specific differential expression patterns of OXPHOS complex I subunit-related genes provide valuable insights into the importance of their integrity for tissue-specific energy requirements, mitochondrial function, and their implications for buffalo's productive and reproductive health.