Mitochondrial Gene Sequence Analysis Of Parasitic Plant Cynomorium And Horizontal Gene Transfer Research

Horizontal gene transfer (HGT) phenomenon of higher plants has been discovered and investigated in recent years, and it is very important to eukaryotic genomes evolution. The parasitic relationship of higher plants is an important way for HGT. Because of its specific structure of mitochondrion genome, HGT is more likely to happen in mitochondrial genes than nuclear genes and chloroplast genes. There are few reports on HGT in higher plants, and the mechanism of HGT was divergent in different plants. We selected medicinal parasitic plant Cynomorium songaricum Pupr. for the study, we had cloned and analyzed sequences of mitochondria genes coxl, cox2, naadl, cob, nad5, nadl, rps3, nad6; nad9, rpl5, ccmC and cox3 gene, aiming to elucidate the phenomena of gene transfer. The results are as follows:1. Using the maximum likelihood method to analyze the introns and exons of coxl and cox2 gene, we found that the phylogeny of coxl gene intron were not consistent with phylogenetic relationship, suggesting that coxl intron may have HGT phenomenon.2. We compared the average distance of exon and intron sequences of mitochondrial genes coxl, cox2 and nadl in six different populations of C. songaricum, and found that the genetic distance of cox2 and nadl genes are relatively high between populations, the genetic distance of coxl gene was relatively low between differences populations, and homology of coxl intron had reached to 100% in six different populations. The results suggested the intron of coxl gene may have function. Bioinformatics analysis showed that the intron most likely coded for endonuclease, and endonuclease is thought to promote the intron to transfer.3. RT-PCR indicated coxl intron can be transcribed to mRNA independently.4. We have amplified and analyzed the sequences of mitochondrial genes cob, nad5, nad7, rps3, nad6, nad9, rpl5, ccmC and cox3 in medicinal parasitic plant C. songaricum and its host. The phylogeny analysis of nad6 and nad9 showed that C. songaricum and its host Nitraria tangutorum Bobr. were in the same branch, indicating that the nad6 and nad9 genes of C.songaricum and Nitraria may have HGT phenomenon; The high similarities of nad6 and nad9 gene nucleotide sequences and amino acid sequences between C.songaricum and Nitraria, were high indicated that nad6 and nad9 genes of C.songaricum and Nitraria may have similar functions.