Cytochrome b or cytochrome c oxidase subunit I for mammalian species identification—An answer to the debate

Background and Aim: India has large varieties (recognized, unrecognized) of native chickens (Desi) scattered throughout the country, managed under scavenging system different from commercial chicken breeds. However, they are less investigated for genetic diversity they harbor. The present study was planned to evaluate genetic diversity among two native chicken populations of North Gujarat (proposed Aravali breed) and South Gujarat (Ankleshwar breed). Aravali chicken, a distinct population with unique characters different from the registered chicken breeds of India is under process to be registered as a new chicken breed of Gujarat, India. Materials and Methods: Two mitochondrial markers, namely, cytochrome c oxidase subunit I (COX I) and cytochrome b (Cyt b) genes were studied across 10 birds from each population. Methodology included sample collection (blood), DNA isolation (manual), polymerase chain reaction amplification of mitochondrial genes, Sanger sequencing, and purification followed by data analysis using various softwares. Results: Haplotype analysis of the COX I gene unveiled a total eight and three haplotypes from the Aravali and Ankleshwar populations, respectively, with haplotype diversity (Hd) of 92.70 % for the Aravali and 34.50% for the Ankleshwar breed. Haplotype analysis of the Cyt b gene revealed a total of four haplotypes from the Aravali population with 60% Hd and no polymorphism in Ankleshwar breed. The phylogenetic analysis uncovered Red Jungle Fowl and Gray Jungle Fowl as prime roots for both populations and all domestic chicken breeds. Conclusion: Study findings indicated high genetic variability in Aravali chicken populations with COX I mitochondrial marker being more informative for evaluating genetic diversity in chickens.

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Deletion of the Leader Peptide of the Mitochondrially Encoded Precursor of Saccharomyces cerevisiae Cytochrome c Oxidase Subunit II

Genetics ◽

10.1093/genetics/145.4.903 ◽

1997 ◽

Vol 145 (4) ◽

pp. 903-910 ◽

Cited By ~ 3

Author(s):

A Thomas Torello ◽

Michael H Overholtzer ◽

Vicki L Cameron ◽

Nathalie Bonnefoy ◽

Thomas D Fox

Keyword(s):

Saccharomyces Cerevisiae ◽

Cytochrome C ◽

Cytochrome C Oxidase ◽

Cytochrome B ◽

Mitochondrial Gene ◽

Leader Peptide ◽

Intermembrane Space ◽

Gene Encoding ◽

Amino Terminal ◽

Oxidase Subunit

Cytochrome c oxidase subunit II (Cox2p) of Saccharomyces cerevisiae is synthesized within mitochondria as a precursor, pre-Cox2p. The 15-amino acid leader peptide is processed after export to the intermembrane space. Leader peptides are relatively unusual in mitochondrially coded proteins: indeed mammalian Cox2p lacks a leader peptide. We generated two deletions in the S. cerevisiae COX2 gene, removing either the leader peptide (cox2-20) or the leader peptide and processing site (cox2-21) without altering either the promoter or the mRNA-specific translational activation site. When inserted into mtDNA, both deletions substantially reduced the steady-state levels of Cox2p and caused a tight nonrespiratory phenotype. A respiring pseudorevertant of the cox2-20 mutant was heteroplasmic for the original mutant mtDNA and a ρ–-mtDNA whose deletion fused the first 251 codons of the mitochondrial gene encoding cytochrome b to the cox2-20 sequence. The resulting fusion protein was processed to yield functional Cox2p. Thus, the presence of amino-terminal cytochrome b sequence bypassed the need for the pre-Cox2p leader peptide. We propose that the pre-Cox2p leader peptide contains a targeting signal necessary for membrane insertion, without which it remains in the matrix and is rapidly degraded.

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