Submitted to: Genome Announcements
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2017
Publication Date: 4/20/2017
Citation: Davis, R.E., Shao, J.Y., Zhao, Y., Gasparich, G.E., Gaynor, B.J., Donofrio, N. 2017. Complete genome sequence of Spiroplasma citri strain R8-A2T, causal agent of stubborn disease in Citrus spp. Genome Announcements. 5:e00206-17.

Interpretive Summary: Citrus plants growing in arid and semi-arid regions are affected by stubborn disease (citrus little leaf disease). Symptoms include mottled and small leaves, abnormally shaped fruit, stunting of trees, and reduced production of fruits. Originally observed in California ca. 1915, the disease was first mistakenly attributed to infection by a virus. Later, the disease was attributed to a (nonhelical) mycoplasma, based on results from electron microscopy that failed to reveal the three-dimensional structure of the disease agent. Subsequently, in vitro culture of the presumed mycoplasma was reported. Only after the discovery by R.E. Davis of a new form of cellular pathogen - helical and motile cell wall-less bacteria, for which Davis coined the name spiroplasma - was the citrus stubborn agent recognized to be a spiroplasma, and a new species was described, Spiroplasma citri. The present paper provides the second completely sequenced genome of a plant disease-causing spiroplasma, and the first completely sequenced genome of a strain of S. citri. The completed gene decoding will interest quarantine agencies, diagnostics companies, microbiologists, plant pathologists, entomologists, professors, students, plant breeders, and seed companies. Availability of the S. citri complete genome should facilitate studies to elucidate the evolutionary biology of plant-pathogenic spiroplasmas.

Technical Abstract: Spiroplasma citri is the causal agent of stubborn disease in Citrus spp., as well as the cause of diseases in numerous other plant genera. Here we report the nucleotide sequence of the 1,599,709 bp circular chromosome and two plasmids of strain R8-A2T. This information will facilitate comparative genome analyses aimed at understanding spiroplasma pathogenicity and evolutionary adaptations to varied lifestyles in plants and arthropod hosts.