The complete chloroplast genome sequence of American elm (Ulmus americana) and comparative genomics of related species

Abstract

ABSTRACTAmerican elm,Ulmus americanaL., was cultivated widely in USA and Canada as a landscape tree, but the genome of this important species is poorly characterized. For the first time, we describe the sequencing and assembly of the chloroplast genomes of two American elm genotypes (RV16 and Am57845). The complete chloroplast genome ofU. americanaranged from 158,935-158,993 bp. The genome contains 127 genes, including 85 protein-coding genes, 34 tRNA genes and 8 rRNA genes. Between the two American elm chloroplasts we sequenced, we identified 240 sequence variants (SNPs and indels). To evaluate the phylogeny of American elm, we compared the chloroplast genomes of two American elms along with seven Asian elm species and twelve other chloroplast genomes available through the NCBI database. As expected,Ulmuswas closely related toMorusandCannabis, as all three genera are assigned to the Urticales. Comparison of American elm with Asian elms revealed thattrnH was absent from the chloroplast of American elm but not most Asian elms; conversely,petB,petD,psbL,trnK, andrps16 are present in the American elm but absent from all Asian elms. The complete chloroplast genome ofU. americanawill provide useful genetic resources for characterizing the genetic diversity ofU. americanaand potentially help to conserve natural populations of American elm.