title: High-throughput discovery of chloroplast and mitochondrial DNA polymorphisms in Brassicaceae species by ORG-EcoTILLING.
abstract: BACKGROUND
  Information on polymorphic DNA in organelle genomes is essential for evolutionary and ecological studies. However, it is challenging to perform high-throughput investigations of chloroplast and mitochondrial DNA polymorphisms. In recent years, EcoTILLING stands out as one of the most universal, low-cost, and high-throughput reverse genetic methods, and the identification of natural genetic variants can provide much information about gene function, association mapping and linkage disequilibrium analysis and species evolution. Until now, no report exists on whether this method is applicable to organelle genomes and to what extent it can be used.
  
  
  RESULTS
  To address this problem, we adapted the CEL I-based heteroduplex cleavage strategy used in Targeting Induced Local Lesions in Genomes (TILLING) for the discovery of nucleotide polymorphisms in organelle genomes. To assess the applicability and accuracy of this technology, designated ORG-EcoTILLING, at different taxonomic levels, we sampled two sets of taxa representing accessions from the Brassicaceae with three chloroplast genes (accD, matK and rbcL) and one mitochondrial gene (atp6). The method successfully detected nine, six and one mutation sites in the accD, matK and rbcL genes, respectively, in 96 Brassica accessions. These mutations were confirmed by DNA sequencing, with 100% accuracy at both inter- and intraspecific levels. We also detected 44 putative mutations in accD in 91 accessions from 45 species and 29 genera of seven tribes. Compared with DNA sequencing results, the false negative rate was 36%. However, 17 SNPs detected in atp6 were completely identical to the sequencing results.
  
  
  CONCLUSIONS
  These results suggest that ORG-EcoTILLING is a powerful and cost-effective alternative method for high-throughput genome-wide assessment of inter- and intraspecific chloroplast and mitochondrial DNA polymorphisms. It will play an important role in evolutionary and ecological biology studies, in identification of related genes associated with agronomic importance such as high yield and improved cytoplasmic quality, and for identifying mitochondrial point mutations responsible for diseases in humans and other animals.
authors.affiliation: Oil Crop Research Institute, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Oil Crops, Ministry of Agriculture, Wuhan, China.
authors.forename: Chang-Li
authors.initials: CL
authors.lastname: Zeng
authors.forename: Guang-Yong
authors.initials: GY
authors.lastname: Wang
authors.forename: Jian-Bo
authors.initials: JB
authors.lastname: Wang
authors.forename: Gui-Xin
authors.initials: GX
authors.lastname: Yan
authors.forename: Bi-Yun
authors.initials: BY
authors.lastname: Chen
authors.forename: Kun
authors.initials: K
authors.lastname: Xu
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Gui-Zhen
authors.initials: GZ
authors.lastname: Gao
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Wu
authors.forename: Bo
authors.initials: B
authors.lastname: Zhao
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
mesh_terms: D001483:Base Sequence; D019607:Brassicaceae / Q000235:genetics*; D018742:DNA, Chloroplast / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D060146:Ecotype; D004587:Electrophoresis, Agar Gel; D061125:Genes, Chloroplast / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods*; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D015388:Organelles / Q000235:genetics*; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D015203:Reproducibility of Results; D013045:Species Specificity
chemical_list: D018742:DNA, Chloroplast; D004272:DNA, Mitochondrial