The Influence Of Nuclear Genome on the Evolution of Mitochondrial ATP6 in Wheat

Following their acquisition by eukaryotic cells during endosymbiosis, cytoplasmic organelles followed their own evolutionary pathway under strict control of nuclear genome. Among all eukaryotes, wheat possesses the largest set of alloplsmic lines (those with alien cytoplasm) providing an invaluable resource for analysis of nuclear-cytoplasm interaction and evolutionary investigation of their genome In this study we selected ATP6 gene, as one the most diverse parts of mitochondrial genome among various species. Sanger sequencing was conducted after cloning of this gene from four euoplasmic lines including Triticum timopheevii (G plasmon), T. durum (B plasmon), Triticum taushchii (D plasmon) and T. longissimum (S^v plasmon). ATP6 was also sequenced from an alloplasmic line with T. longissimum cytoplasm and T.durum nucleus to further analyze the nuclear effect on mitochondrial genome evolution. Our results reveal a major structural difference between ATP6 of G/B plasmons in comparisons with their counterpart in D/S^v plasmon that may have led to cytoplasmic specification. Although comparative study among consensus sequences couldn’t identify any SNP between G and B plasmons, twelve SNPs were found between D and S^v in ATP6 region. Lack of SNP between G and B further confirms the close evolutionary relationship between these two cytoplasms.  Variation among clones of each line considered as different mitotypes in heteroplasmy condition. Interestingly both G/B and D/S^v forms of ATP6 were detected in alloplasmic (lo) durum line as an evidence of paternal leakage or nucleus induced stoichiometric shift.