Format: ORAL

Qing Liu1,2,3*, Hongyu Yuan1,2,4, Jiaxin Xu5, Dongli Cui1,2,4, Gui Xiong1,2,4, Trude Schwarzacher1,2,6, and John Seymour Heslop-Harrison1,2,6*Qing Liu1,2,3*, Hongyu Yuan1,2,4, Jiaxin Xu5, Dongli Cui1,2,4, Gui Xiong1,2,4, Trude Schwarzacher1,2,6, and John S. Heslop-Harrison1,2,6*

1 Key Laboratory of Plant Resources Conservation and Sustainable Utilization / Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China. 2 South China National Botanical Garden, Guangzhou, China. 3 Center for Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou 510650, China. 4 University of Chinese Academy of Sciences, Beijing, China. 5 College of Plant Protection, South China Agricultural University, Guangzhou, China 6 University of Leicester, Department of Genetics and Genome Biology, Institute for Environmental Futures, Leicester , UK

Background: Avena longiglumis Durieu (2n=2x=14) is a wild relative of cultivated oat (Avena sativa, 2n=6x=42) with good agronomic and nutritional traits. The plant mitochondrial genome has a complex organization and carries genetic traits of value in exploiting genetic resources, not least male sterility alleles used to generate F1 hybrid seed. Therefore, we aimed to complement the chromosomal-level nuclear and chloroplast genome assemblies of A. longiglumis with the complete assembly of the mitochondrial genome (mitogenome) based on Illumina and ONT long reads, comparing its structure with Poaceae species. Results: The complete mitochondrial genome of A. longiglumiscan be represented by one master circular genome being 548,445 bp long with a GC content of 44.05%. It can be represented in four circular DNA molecules (isoforms or contigs), with multiple alternative configurations mediated by long (4,10031,235 bp) and medium (144792 bp) size repeats. Thirty-five unique protein-coding genes, three unique rRNA genes, and 11 unique tRNA genes were identified. The mitogenome was rich in duplications (up to 233 kb long) and multiple tandem or simple sequence repeats, together accounting for more than 42.5% of the length. We identified homologous sequences between the mitochondrial, plastid and nuclear genomes, including exchange of eight plastid-derived tRNA genes, and nuclear-derived retroelement fragments. At least 85% of the mitogenome is duplicating in the A. longiglumis nuclear genome. We identified 269 RNA editing sites in mitochondrial protein-coding genes including stop codons truncating ccmFC transcripts. Conclusions: Comparative analysis with Poaceae species revealed the dynamic and ongoing evolutionary changes in mitochondrial genome structure and gene content. The complete mitochondrial genome of A. longiglumis, completes the last link of the oat reference genome and lays the foundation for oat breeding and exploiting the biodiversity in the genus.