scholarly journals Modulation of plant defense responses by Salicylate hydroxylase of Candidatus Liberibacter asiaticus

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Pankaj Trivedi ◽  
Nian Wang
Keyword(s):  
Plant Defense ◽  
Defense Responses ◽  
Plant Defense Responses ◽  
Candidatus Liberibacter Asiaticus ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus

scholarly journals A Secreted ‘Candidatus Liberibacter asiaticus’ Peroxiredoxin Simultaneously Suppresses Both Localized and Systemic Innate Immune Responses In Planta

2018 ◽  
Vol 31 (12) ◽  
pp. 1312-1322 ◽  
Author(s):  
Mukesh Jain ◽  
Alejandra Munoz-Bodnar ◽  
Shujian Zhang ◽  
Dean W. Gabriel
Keyword(s):  
Plant Defense ◽  
Transcriptional Activation ◽  
Lipid Membranes ◽  
Transcript Abundance ◽  
Housekeeping Gene ◽  
Candidatus Liberibacter Asiaticus ◽  
In Planta ◽  
Hypersensitive Cell Death ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus

The oxidative (H2O2) burst is a seminal feature of the basal plant defense response to attempted pathogen invasions. In ‘Candidatus Liberibacter asiaticus’ UF506, expression of the SC2 prophage-encoded secreted peroxidase (F489_gp15) increases bacterial fitness and delays symptom progression in citrus. Two chromosomal 1-Cys peroxiredoxin genes, CLIBASIA_RS00940 (Lasprx5) and CLIBASIA_RS00445 (Lasbcp), are conserved among all sequenced ‘Ca. L. asiaticus’ strains, including those lacking prophages. Both LasBCP and LasdPrx5 have only a single conserved peroxidatic Cys (CP/SH) and lack the resolving Cys (CR/SH). Lasprx5 appeared to be a housekeeping gene with similar moderate transcript abundance in both ‘Ca. L. asiaticus’–infected psyllids and citrus. By contrast, Lasbcp was expressed only in planta, similar to the expression of the SC2 peroxidase. Since ‘Ca. L. asiaticus’ is uncultured, Lasbcp and Lasprx5 were functionally validated in a cultured surrogate species, Liberibacter crescens, and both genes significantly increased oxidative stress tolerance and cell viability in culture. LasBCP was nonclassically secreted and, in L. crescens, conferred 214-fold more resistance to tert-butyl hydroperoxide (tBOOH) than wild type. Transient overexpression of Lasbcp in tobacco suppressed H2O2-mediated transcriptional activation of RbohB, the key gatekeeper of the systemic plant defense signaling cascade. Lasbcp expression did not interfere with the perception of ‘Ca. L. asiaticus’ flagellin (flg22Las) but interrupted the downstream activation of RbohB and stereotypical deposition of callose in tobacco. Critically, LasBCP also protected against tBOOH-induced peroxidative degradation of lipid membranes in planta, preventing subsequent accumulation of antimicrobial oxylipins that can also trigger the localized hypersensitive cell death response.

scholarly journals Identification of Gene Candidates Associated with Huanglongbing Tolerance, Using ‘Candidatus Liberibacter asiaticus’ Flagellin 22 as a Proxy to Challenge Citrus

2018 ◽  
Vol 31 (2) ◽  
pp. 200-211 ◽  
Author(s):  
Qingchun Shi ◽  
Vicente J. Febres ◽  
Shujian Zhang ◽  
Fahong Yu ◽  
Greg McCollum ◽  
...  
Keyword(s):  
Quantitative Polymerase Chain Reaction ◽  
Citrus Canker ◽  
Defense Responses ◽  
Candidatus Liberibacter Asiaticus ◽  
Tolerance Mechanisms ◽  
Molecular Pattern ◽  
Number Of Genes ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Polymerase Chain

The 22–amino acid (flg22) pathogen-associated molecular pattern from the flagellin of Xanthomonas citri subsp. citri has been shown to induce defense responses correlated with citrus canker resistance. Here, flg22 of ‘Candidatus Liberibacter asiaticus’, the putative causal agent of Huanglongbing (HLB), elicited differential defense responses that were weaker than those from Xcc-flg22, between those of the HLB-tolerant mandarin cultivar Sun Chu Sha and susceptible grapefruit cultivar Duncan. Transcriptomics was used to compare the effect of CLas-flg22 and Xcc-flg22 between the citrus genotypes and identified 86 genes induced only by CLas-flg22 in the tolerant mandarin. Expression of 16 selected genes was validated, by reverse transcription-quantitative polymerase chain reaction, and was evaluated in citrus during ‘Ca. L. asiaticus’ infection. Differential expression of a number of genes occurred between tolerant and susceptible citrus infected with ‘Ca. L. asiaticus’, suggesting their involvement in HLB tolerance. In addition, several genes were similarly regulated by CLas-flg22 and ‘Ca. L. asiaticus’ treatments, while others were oppositely regulated in the tolerant mandarin, suggesting similarity and interplay between CLas-flg22 and ‘Ca. L. asiaticus’–triggered defenses. Genes identified are valuable in furthering the study of HLB tolerance mechanisms and, potentially, for screening for HLB-tolerant citrus using CLas-flg22 as a pathogen proxy.

scholarly journals Not Just a Cycle: Three gab genes Enable the Non-cyclic Flux Toward Succinate Via GABA Shunt in ‘Candidatus Liberibacter asiaticus’-infected citrus

2021 ◽  
Author(s):  
Yasser Nehela ◽  
Nabil Killiny
Keyword(s):  
Tca Cycle ◽  
Defense Responses ◽  
Candidatus Liberibacter Asiaticus ◽  
Amino Acid Permease ◽  
Phytopathogenic Bacterium ◽  
Gaba Shunt ◽  
Semialdehyde Dehydrogenase ◽  
The Tca Cycle ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus

Although the mitochondria retain all required enzymes for an intact tricarboxylic acid (TCA) cycle, plants might shift the cyclic flux from the TCA cycle to an alternative non-cyclic pathway via γ-aminobutyric acid (GABA) shunt under specific physiological conditions. We hypothesize that several genes may ease this non-cyclic flux and contribute to the citrus response to the phytopathogenic bacterium ‘Candidatus Liberibacter asiaticus’, the causal agent of Huanglongbing in citrus. To test this hypothesis, we used multi-omics techniques (metabolomics, fluxomics, and transcriptomics) to investigate the potential role(s) of putative gab homologies from Valencia sweet orange (Citrus sinensis). Our findings showed that ‘Ca. L. asiaticus’ significantly increased the endogenous GABA and succinate content but decreased ketoglutarate in infected citrus plants. Citrus genome harbors three putative gab genes including amino-acid permease (aka GABA permease; CsgabP), GABA transaminase (CsgabT), and succinate-semialdehyde dehydrogenase (aka GABA dehydrogenase; CsgabD). The transcript levels of CsgabP, CsgabT, and CsgabD were upregulated in citrus leaves upon the infection with ‘Ca. L. asiaticus’ and after the exogenous application of GABA or deuterium-labeled GABA isotope (GABA-D6). Moreover, our finding showed that exogenously applied GABA is quickly converted to succinate and fed into the TCA cycle. Likewise, the fluxomics study showed that GABA-D6 is rapidly metabolized to succinate-D4. Our work proved that GABA shunt and three predicated gab genes from citrus, support the upstream non-cyclic flux toward succinate rather than an intact TCA cycle and contribute to citrus defense responses to ‘Ca. L. asiaticus’.

scholarly journals An efficient direct screening system for microorganisms that activate plant immune responses based on plant–microbe interactions using cultured plant cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mari Kurokawa ◽  
Masataka Nakano ◽  
Nobutaka Kitahata ◽  
Kazuyuki Kuchitsu ◽  
Toshiki Furuya
Keyword(s):  
Immune Responses ◽  
Plant Defense ◽  
Pseudomonas Syringae ◽  
Large Scale ◽  
Plant Cells ◽  
Defense Responses ◽  
Root Tip ◽  
General Strategy ◽  
Plant Defense Responses ◽  
Microbe Interactions

AbstractMicroorganisms that activate plant immune responses have attracted considerable attention as potential biocontrol agents in agriculture because they could reduce agrochemical use. However, conventional methods to screen for such microorganisms using whole plants and pathogens are generally laborious and time consuming. Here, we describe a general strategy using cultured plant cells to identify microorganisms that activate plant defense responses based on plant–microbe interactions. Microbial cells were incubated with tobacco BY-2 cells, followed by treatment with cryptogein, a proteinaceous elicitor of tobacco immune responses secreted by an oomycete. Cryptogein-induced production of reactive oxygen species (ROS) in BY-2 cells served as a marker to evaluate the potential of microorganisms to activate plant defense responses. Twenty-nine bacterial strains isolated from the interior of Brassica rapa var. perviridis plants were screened, and 8 strains that enhanced cryptogein-induced ROS production in BY-2 cells were selected. Following application of these strains to the root tip of Arabidopsis seedlings, two strains, Delftia sp. BR1R-2 and Arthrobacter sp. BR2S-6, were found to induce whole-plant resistance to bacterial pathogens (Pseudomonas syringae pv. tomato DC3000 and Pectobacterium carotovora subsp. carotovora NBRC 14082). Pathogen-induced expression of plant defense-related genes (PR-1, PR-5, and PDF1.2) was enhanced by the pretreatment with strain BR1R-2. This cell–cell interaction-based platform is readily applicable to large-scale screening for microorganisms that enhance plant defense responses under various environmental conditions.

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