First Insights into the Mitochondrial Genome of Perennial Ryegrass (Lolium perenne)

Abstract

Plant mitochondrial genomes encode the majority of genes that are involved in aerobic respiration which provides energy for the plant cell. To date only 32 plant mitochondrial genomes have been sequenced completely and only one from the Pooideae subfamily to which Lolium belongs. We aimed to sequence the complete mitochondrial genome of perennial ryegrass to assess its variation in comparison to other grasses and to provide insights into agronomically important traits such as cytoplasmic male sterility. We found all 33 known plant mitochondria protein-coding genes, three ribosomal RNA and 20 transfer RNA genes. However, plant mitochondrial genomes are complex in their structure and exhibit a low degree of conservation in relation to other mitochondrial genomes. Thus, a complete assembly of the perennial ryegrass mitochondrial genome was not possible due to the lack of a suitable reference genome and the high variability. However, we reduced the large number of contigs to a set of 43 that contained either protein-coding genes or consisted of more than 10 kb. Based on this data set we found evidence for intracellular gene transfer events from the chloroplast genome to the mitochondrial genome and possibly duplicated gene exons. We estimated the size of the mitochondrial genome of perennial ryegrass to be approximately 565 kb.