Mitochondrial Genome Sequence Analysis Of A Brassica Juncea Landrace

B. juncea that has better resistance to stress that other Brassica species, is a germplasm resource of important value to rapeseed breeding. Our research completes mitochondrial genome sequencing of a B. juncea landrace Jiangpu-yejiecai, and analyzed the genome sequence. This research has bettered the understanding the B. juncea mitochondrial genome and the relationship of the mitochondrial genome with other Brassica mitotypes. Main results are as follows:1. Analysis of the mitochondrial genome sequence. Using Roche 454 high-throughput sequencing, an entire mitochondrial genome sequence of the B. juncea landrace Jiangpu-yejiecai, is obtained, which is a circular mitochondrial DNA sequence length of 219,766bp, named jun mitotype. Compared with the nap mitotype in B. napus, jun mitotype contains the insertion and deletion sequence which is totally about 9.4kb specific sequences. Jun mitotype also contains 10 fragments which are longer than 2kb and more than 99% homology to nap mitotype. Compared with pol mitotype in B. napus, jun mitotype contains a specific sequences of 813bp. SNPs of jun in comparisons with nap, pol mitotypes, is respectively 155 and 20. The single nucleotide variations occurred usually in the mitochondrial non-coding regions, and the three genomes are highly conserved in the coding genes. Jun mitotype contains numerous small fragments repeat sequences, a pair of 2.4 kb large fragment repeat sequences and tandem repeat sequences. The repeats account for 7.50% of the genome sequence.2. Gene analysis.33 protein-coding genes,3 ribosomal RNA genes and 18 tRNA genes were identified in jun mitotype. The total length of function-known genes is 38,139bp, accounting for 17.35% of jun genome. Compared with nap, function-known gene coxl, cox2, atpl, trnC and trnE in jun mitotype have a nucleotide substitution, but does not affect the gene function. Jun mitotype doesn't contain orf222, but has two copies of trnH gene, however nap mitotype has only one copy. The function-known genes in jun are almost the same to pol mitotype, but it don't contain the orf224. Jun mitotype contains 44 function-unknown ORFs longer than 100 codons. All of the ORFs are the same as pol mitotype, but 8 out of these are different from the nap mitotype. orfl22 and orf132 are present in jun mitotype,but unpresent in nap mitotype.This study has elucidated the difference between B. juncea mitochondrial genome and the B. napus, and also provide the good basis for understanding the mitochondrial genome of Brassica.