Longitudinal transcriptomic, proteomic, and metabolomic analyses of Citrus sinensis (L.) Osbeck graft-inoculated with ‘Candidatus Liberibacter asiaticus’

Authors: CHIN, ELIZABETH - University Of California, Davis; Ramsey, John - John; MISHCHUK, DARYA - University Of California, Davis; SAHA, SURYA - Boyce Thompson Institute; MITROVIC, ELIZABETH - University Of California, Davis; CHAVEZ, JUAN - University Of Washington; Howe, Kevin; ZHONG, XUEFEI - University Of Washington; Polek, Marylou; GODFREY, KRIS - University Of California, Davis; MUELLER, LUKAS - Boyce Thompson Institute; BRUCE, JAMES - University Of Washington; Heck, Michelle; SLUPSKY, CAROLYN - University Of California, Davis

Submitted to: Journal of Proteome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2019
Publication Date: 12/30/2019
Citation: Chin, E., Ramsey, J.S., Mishchuk, D.O., Saha, S., Mitrovic, E., Chavez, J.D., Howe, K.J., Zhong, X., Polek, M., Godfrey, K.E., Mueller, L.A., Bruce, J.E., Heck, M.L., Slupsky, C.M. 2019. Longitudinal transcriptomic, proteomic, and metabolomic analyses of Citrus sinensis (L.) Osbeck graft-inoculated with ‘Candidatus Liberibacter asiaticus’. Journal of Proteome Research. 19(2):719-732. https://doi.org/10.1021/acs.jproteome.9b00616.
DOI: https://doi.org/10.1021/acs.jproteome.9b00616

Interpretive Summary: Citrus trees can be infected for months or years with the bacterium associated with citrus greening disease before they develop visual symptoms. This study used genomics, proteomics, and metabolomics to identify molecular changes in leaves of navel orange trees in response to inoculation with the citrus greening bacterium. We collected leaf samples for analysis every two weeks from replicate healthy and infected trees over the 46 weeks that the plants were maintained in greenhouses. Specific changes in plant genes, proteins, and metabolites were observed as early as eight weeks after infection. These findings enable the development of innovative disease detection technologies, and reveal details of the plant response to infection.

Technical Abstract: ‘Candidatus Liberibacter asiaticus’ (CLas) is the bacterium associated with citrus greening disease (Huanglongbing, HLB). The bacterium can be transmitted between citrus trees by its insect vector, the Asian citrus psyllid, or by graft inoculation. A longitudinal multi-omics study was performed on navel orange plants grafted with either CLas(+) or CLas(-) budwood to understand how CLas affects citrus metabolism and to determine whether infected plants produce systemic signals that can be used to develop improved detection techniques. Following graft inoculation, leaves were collected biweekly over the course of 46 weeks and analyzed using transcriptomics (RNA-seq), proteomics (LC-MS/MS), and metabolomics (1H NMR). Differences in expression of genes and proteins related to plant defense, photosynthesis, and cell wall modification were observed between healthy and infected plants as early as 8 weeks post-grafting. Metabolite analysis revealed higher sugar concentrations in CLas-infected plants at the later stages of infection. These results reveal coordinated changes in greenhouse navel leaves during CLas infection at the transcript, protein, and metabolite levels. These results reveal details of the plant response to the citrus greening bacterium and can be used for development of biomarkers of infection.