The effect of ‘Candidatus Liberibacter asiaticus’ infection on the proteomic profiles and nutritional status of pre-symptomatic and symptomatic grapefruit (Citrus paradisi) plants

Abstract

BackgroundHuanglongbing (HLB) is a highly destructive citrus disease which threatens citrus production worldwide and ‘Candidatus Liberibacter asiaticus’ (Las), a non-culturable phloem-limited bacterium, is an associated causal agent of the disease. To better understand the physiological and molecular processes involved in host responses to Las, 2-DE and mass spectrometry analyses, as well as ICP spectroscopy analysis were employed to elucidate the global protein expression profiles and nutrient concentrations in leaves of Las-infected grapefruit plants at pre-symptomatic or symptomatic stages for HLB.ResultsThis study identified 123 protein spots out of 191 spots that showed significant changes in the leaves of grapefruit plants in response to Las infection and all identified spots matched to 69 unique proteins/peptides. A down-regulation of 56 proteins including those associated with photosynthesis, protein synthesis, and metabolism was correlated with significant reductions in the concentrations of Ca, Mg, Fe, Zn, Mn, and Cu in leaves of grapefruit plants in response to Las infection, particularly in symptomatic plants. Oxygen-evolving enhancer (OEE) proteins, a PSI 9 kDa protein, and a Btf3-like protein were among a small group of proteins that were down-regulated in both pre-symptomatic and symptomatic plants in response to Las infection. Furthermore, a Las-mediated up-regulation of 13 grapefruit proteins was detected, which included Cu/Zn superoxide dismutase, chitinases, lectin-related proteins, miraculin-like proteins, peroxiredoxins and a CAP 160 protein. Interestingly, a Las-mediated up-regulation of granule-bound starch synthase was correlated with an increase in the K concentrations of pre-symptomatic and symptomatic plants.ConclusionsThis study constitutes the first attempt to characterize the interrelationships between protein expression and nutritional status of Las-infected pre-symptomatic or symptomatic grapefruit plants and sheds light on the physiological and molecular mechanisms associated with HLB disease development.

Proteomics analysis reveals novel host molecular mechanisms associated with thermotherapy of ‘Ca. Liberibacter asiaticus’-infected citrus plants

“…This result validates the efficacy of the total protein extraction method used in the current study. Additionally, using PDQuest gel-image analysis software, the mean number of detected spots was over 1250 in the present study (Table 1), compared to less than 800 in our prior study [28]. Thus, the higher protein yields and improved protein coverage observed in the present study compared to our prior study is encouraging and suggests a more exhaustive comparative proteomics analysis.…”

“…The exhaustive total protein extraction method (see Methods section) used in this study produced an average protein yield of over 20 mg g −1 from citrus grapefruit leaves irrespective of Las or heat treatment (Table 1), which is higher than the mean protein yield of approximately 13 mg g −1 from citrus grapefruit leaves in our prior study [28]. This result validates the efficacy of the total protein extraction method used in the current study.…”

“…A prior study by our group showed that Las infection caused a broad down-regulation of chaperone-related proteins in grapefruit plants [28]. Citrus tristeza virus (CTV) exhibits a pathosystem similar to Las, and a proteomic study by Laino et al [35] showed that CTV-tolerant citrus plants generally over-activate the phosphorylation of RuBisCO-binding proteins, chaperones and other reactive oxygen scavenging enzymes.…”

Can CRISPR Win the Battle against Huanglongbing?

“…ATPase alpha subunit was only induced in leaves with HLB symptoms. HLB infected grapefruit showed the similar results regarding to the up-regulated proteins [36]. There were 69 proteins that showed differential expression in Las positive leaves compared with healthy leaves.…”

Molecular mechanisms behind the accumulation of ATP and H2O2 in citrus plants in response to ‘Candidatus Liberibacter asiaticus’ infection

“…8 Identification of the host responses to the pathogen is critical for understanding disease development overall and may be exploited in the formulation of efficient disease management practices. 10 When a pathogen attacks, an array of defense mechanisms become activated within the host plant including both basal defense and gene-for-gene resistance. Jones and Dangl 11 conceptualized the plant immune system using a zig-zag model with three phases.…”