Mitochondrial Genome Sequencing Of Four Cajanus Genotypes

To understand the molecular basis of cytoplasmic male sterility (CMS) in pigeonpea (Cajanus cajan), we sequenced the mitochondrial genomes of three C. cajan lines (male-sterile line ICPA 2039, maintainer line ICPB 2039, hybrid line ICPH 2433) and of the wild relative (C. cajanifolius ICPW 29). A single, circular-mapping molecule of length 545.7 Kb was assembled and annotated for ICPA 2039 line. Sequence annotation predicted 51 genes, including 34 protein-coding, 14 tRNA and 3 rRNA genes. Further the ICPA 2039 mitochondrial genome was used as a reference sequence for comparison to identify polymorphism in the other three genotypes. Detailed analysis of the mitochondrial genomes identified 18 and 13 chimeric mitochondrial open reading frames (ORFs) in ICPA 2039 when compared with ICPW 29 and ICPB 2039 line respectively. Amongst these chimeric ORFs, 13 chimeric ORFs identified in ICPA 2039 on comparison with ICPB 2039, comprising five carry parts of annotated mitochondrial genes, and another eight of them are in proximity to other mitochondrial genes. Together, these represent the most promising candidates for CMS-related mitochondrial rearrangements in pigeonpea.