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CORESTA Meeting, Agronomy/Phytopathology, 2021, Online, AP 31

High quality genome assembly of Nicotiana tabacum

GAYSSANT H.(1); DARNIGE E.(1); COTUCHEAU J.(2); DORLHAC DE BORNE F.(2); JULIO E.(2); ZOUINE M.(1)
(1) Laboratoire de Recherche en Sciences Végétales (LRSV), Université de Toulouse, CNRS, UPS, Toulouse INP, Castanet-Tolosan, France; (2) Imperial Tobacco Limited and Imperial Brands PLC Companies, Bergerac, France

Nicotiana tabacum, or cultivated tobacco, is an important plant model whose genome has been explored recently. However, the previous tobacco assemblies based on short reads sequencing showed some flaws. Thanks to new sequencing technologies, the genome assembly quality and its completeness was improved. Using 10X Genomics linked read and Hi-C data, we first produced a 4.2 Gb draft genome assembly (N50 = 61Mb, L50=19).

By anchoring the genetic maps, we generated a 3,04 Gb chromosome level genome assembly. In total, 244 scaffolds were anchored into 24 pseudomolecules with single nucleotide polymorphism (SNPs) and simple-sequence repeats (SSRs) genetic markers. The completeness of the genome assembly has been checked by Benchmarking Universal Single-Copy Orthologs genes analysis (BUSCO). The current genome assembly showed the highest BUSCO score of 93.5 % compared to the published tobacco genomes. Previous studies have shown that tobacco descends from two ancestral diploids plants: Nicotiana sylvestris and Nicotiana tomentosiformis. By proceeding to the mapping of short reads generated from the genomes of these two presumed ancestors on the tobacco pseudomolecules, we were able to pinpoint which tobacco genome region corresponds to which ancestor allowing to gain insight into the evolutionary history of the current tobacco genome. The release of this chromosome-scale genome will provide an important resource for further studies at the fundamental and applied research level.