title: Transient Expression of Candidatus Liberibacter Asiaticus Effector Induces Cell Death in Nicotiana benthamiana.
abstract: Candidatus Liberibacter asiaticus "Las" is a phloem-limited bacterial plant pathogen, and the most prevalent species of Liberibacter associated with citrus huanglongbing (HLB), a devastating disease of citrus worldwide. Although, the complete sequence of the Las genome provides the basis for studying functional genomics of Las and molecular mechanisms of Las-plant interactions, the functional characterization of Las effectors remains a slow process since remains to be cultured. Like other plant pathogens, Las may deliver effector proteins into host cells and modulate a variety of host cellular functions for their infection progression. In this study, we identified 16 putative Las effectors via bioinformatics, and transiently expressed them in Nicotiana benthamiana. Diverse subcellular localization with different shapes and aggregation patterns of the effector candidates were revealed by UV- microscopy after transient expression in leaf tissue. Intriguingly, one of the 16 candidates, Las5315mp (mature protein), was localized in the chloroplast and induced cell death at 3 days post inoculation (dpi) in N. benthamiana. Moreover, Las5315mp induced strong callose deposition in plant cells. This study provides new insights into the localizations and potential roles of these Las effectors in planta.
authors.affiliation: U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture Fort Pierce, FL, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Pitino
authors.affiliation: U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture Fort Pierce, FL, USA.
authors.forename: Cheryl M
authors.initials: CM
authors.lastname: Armstrong
authors.affiliation: Institute of Food and Agricultural Sciences, Department of Plant Pathology, Indian River Research and Education Center, University of Florida Fort Pierce, FL, USA.
authors.forename: Liliana M
authors.initials: LM
authors.lastname: Cano
authors.affiliation: U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture Fort Pierce, FL, USA.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Duan
keywords: Candidatus Liberibacter asiaticus; Nicotiana benthamiana; bacterial effectors; callose deposition; cell death; chloroplast localization; huanglongbing