Novel insights into the Elm Yellows phytoplasma genome and into the metagenome of Elm Yellows-infected elms

Authors: ROSA, CRISTINA - Pennsylvania State University; MARGARIA, PAOLO - Pennsylvania State University; Geib, Scott; Scully, Erin

Submitted to: Northern Research Station Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/17/2017
Publication Date: 9/27/2017
Citation: Rosa, C., Margaria, P., Geib, S.M., Scully, E.D. 2017. Novel insights into the Elm Yellows phytoplasma genome and into the metagenome of Elm Yellows-infected elms. Northern Research Station Proceedings. Proceedings of the American Elm Restoration Workshop 2016 p. 49-67. Lewis Center, OH: U.S. Forest Service, Northern Research Station.

Interpretive Summary: In North America, American elms were originally present throughout the northeastern United States and southeastern Canada and, due to their resilience in urban environments, they were among the most commonly used landscape trees in North America. However, Dutch elm disease (DED) and Elm yellows disease (EY) have killed large numbers of elm trees since the 1940s and the diseases continue to spread throughout the southern and western regions of the United States. EY, together with DED, have been responsible for the death of most of the American elm species throughout these regions. although the prevalence of EY in American elm trees has increased recently, the interactions between the tree and this pathogen that contribute to the progression of the disease remain poorly defined due largely to the inability to culture this pathogen in the lab. In this work, we sampled EY sequences from an infected elm tree and identified several genes that are likely critical for disease development. These sequences provide a basic step towards understanding how EY invades elm trees and evades their immune system and can serve as targets for reducing infection rates.

Technical Abstract: In North America, American elms were historically present throughout the northeastern United States and southeastern Canada. The longevity of these trees, their resistance to the harsh urban environment, and their aesthetics led to their wide use in landscaping and streetscaping over several decades. American elms were one of most cultivated plants in the United States until the arrival of Dutch elm disease (DED)(OEPP/EPPO 1982) and Elm yellows disease (EY)(OEPP/EPPO 1979; Swingle 1942). EY epidemics have killed large numbers of elm trees in the Northeastern United States beginning in the 1940s (Sinclair 1972; Carter and Carter 1974; Lanier et al. 1988). Since then, the disease has gradually been spreading to the southern and western regions of the United States while remaining endemic in the Northeast. Today EY, together with DED, is responsible for the death of most of the American species of elm trees, including (Ulmus americana(L.), U.rubra(Muh.), U.alata(Michx.), U.crassifolia(Nutt.), U.serotina(Sarg)) and of some of their natural hybrids (i.e. U.pumila x rubra). Here, we performed next-generation sequencing on EY infected elm trees to discover EY effectors genes involved in plant-phytoplasma interactions and to survey the metagenome of the infected elms. This project serves as a basic step to understand how EY infection shapes the elm microbial communities and, in the long term, will lead to a better understanding of the pathogenesis of EY infection in elm and the interactions between EY with its leafhopper vectors.