scholarly journals Overexpression of Salicylic Acid Carboxyl Methyltransferase (CsSAMT1) Enhances Tolerance to Huanglongbing Disease in Wanjincheng Orange (Citrus sinensis (L.) Osbeck)

2021 ◽  
Vol 22 (6) ◽  
pp. 2803
Author(s):  
Xiuping Zou ◽  
Ke Zhao ◽  
Yunuo Liu ◽  
Meixia Du ◽  
Lin Zheng ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Citrus Sinensis ◽  
Plant Defenses ◽  
Citrus Fruits ◽  
Wild Type ◽  
Citrus Industry ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus

Citrus Huanglongbing (HLB) disease or citrus greening is caused by Candidatus Liberibacter asiaticus (Las) and is the most devastating disease in the global citrus industry. Salicylic acid (SA) plays a central role in regulating plant defenses against pathogenic attack. SA methyltransferase (SAMT) modulates SA homeostasis by converting SA to methyl salicylate (MeSA). Here, we report on the functions of the citrus SAMT (CsSAMT1) gene from HLB-susceptible Wanjincheng orange (Citrus sinensis (L.) Osbeck) in plant defenses against Las infection. The CsSAMT1 cDNA was expressed in yeast. Using in vitro enzyme assays, yeast expressing CsSAMT1 was confirmed to specifically catalyze the formation of MeSA using SA as a substrate. Transgenic Wanjincheng orange plants overexpressing CsSAMT1 had significantly increased levels of SA and MeSA compared to wild-type controls. HLB resistance was evaluated for two years and showed that transgenic plants displayed significantly alleviated symptoms including a lack of chlorosis, low bacterial counts, reduced hyperplasia of the phloem cells, and lower levels of starch and callose compared to wild-type plants. These data confirmed that CsSAMT1 overexpression confers an enhanced tolerance to Las in citrus fruits. RNA-seq analysis revealed that CsSAMT1 overexpression significantly upregulated the citrus defense response by enhancing the transcription of disease resistance genes. This study provides insight for improving host resistance to HLB by manipulation of SA signaling in citrus fruits.

scholarly journals ‘Candidatus Liberibacter asiaticus’ Encodes a Functional Salicylic Acid (SA) Hydroxylase That Degrades SA to Suppress Plant Defenses

2017 ◽  
Vol 30 (8) ◽  
pp. 620-630 ◽  
Author(s):  
Jinyun Li ◽  
Zhiqian Pang ◽  
Pankaj Trivedi ◽  
Xiaofeng Zhou ◽  
Xiaobao Ying ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Enzymatic Activity ◽  
Plant Defenses ◽  
Plant Diseases ◽  
Transgenic Tobacco Plants ◽  
Candidatus Liberibacter Asiaticus ◽  
Tobacco Plants ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Management Approaches

Pathogens from the fastidious, phloem-restricted ‘Candidatus Liberibacter’ species cause the devastating Huanglongbing (HLB) disease in citrus worldwide and cause diseases on many solanaceous crops and plants in the Apiaceae family. However, little is known about the pathogenic mechanisms due to the difficulty in culturing the corresponding ‘Ca. Liberibacter’ species. Here, we report that the citrus HLB pathogen ‘Ca. L. asiaticus’ uses an active salicylate hydroxylase SahA to degrade salicylic acid (SA) and suppress plant defenses. Purified SahA protein displays strong enzymatic activity to degrade SA and its derivatives. Overexpression of SahA in transgenic tobacco plants abolishes SA accumulation and hypersensitive response (HR) induced by nonhost pathogen infection. By degrading SA, ‘Ca. L. asiaticus’ not only enhances the susceptibility of citrus plants to both nonpathogenic and pathogenic Xanthomonas citri but also attenuates the responses of citrus plants to exogenous SA. In addition, foliar spraying of 2,1,3-benzothiadiazole and 2,6-dichloroisonicotinic acid, SA functional analogs not degradable by SahA, displays comparable (and even better) effectiveness with SA in suppressing ‘Ca. L. asiaticus’ population growth and HLB disease progression in infected citrus trees under field conditions. This study demonstrates one or more pathogens suppress plant defenses by degrading SA and establish clues for developing novel SA derivatives-based management approaches to control the associated plant diseases.

scholarly journals Genome Sequence Resource of ‘Candidatus Liberibacter asiaticus’ from Thailand

Plant Disease ◽  
2020 ◽  
Vol 104 (3) ◽  
pp. 624-626
Author(s):  
Tao Li ◽  
Narit Thaochan ◽  
Jiaquan Huang ◽  
Jianchi Chen ◽  
Xiaoling Deng ◽  
...  
Keyword(s):  
Genome Sequence ◽  
Candidatus Liberibacter Asiaticus ◽  
Citrus Industry ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus

‘Candidatus Liberibacter asiaticus’ (Las) is an unculturable α-proteobacterium associated with citrus huanglongbing (HLB), a devastating disease currently threatening the citrus industry worldwide. Here, we present the genome sequence of Las strain TaiYZ2 from an HLB-affected pomelo tree in Hat Yai district, Songkhla Province, Thailand. The TaiYZ2 genome is composed of 1,230,623 bp with G+C content of 36.4%. This is the first Las genome sequence from Thailand, which will enrich current Las genome resource and facilitate HLB research and management.

scholarly journals First report of ‘Candidatus Liberibacter asiaticus’ affecting sour orange in urban areas of Mayabeque, Cuba

2020 ◽  
Author(s):  
Edel Pérez-López ◽  
Tim J. Dumonceaux
Keyword(s):  
Urban Areas ◽  
Sour Orange ◽  
Candidatus Liberibacter Asiaticus ◽  
Citrus Industry ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus ◽  
Molecular Barcode ◽  
Serious Disease ◽  
First Time

Abstract‘Candidatus Liberibacter asiaticus’ (CLas) is an unculturable, Gram-negative, phloem restricted plant pathogenic bacterium associated with a very serious disease of citrus worldwide known as Citrus Huanglongbing (HLB). CLas is widely spread in the Americas. In Cuba, CLas has been associated with HLB symptoms and has seriously affected the Cuban citrus industry. In this short communication we discuss the identification of CLas-infected sour orange in urban areas of Mayabeque Province in Cuba, an area previously unexplored for the presence of HLB, and a host widely cultivated in gardens and yards along Cuba. We used for the first time the bacteria molecular barcode chaperonin-60 universal target (cpn60 UT) to identify and to detect CLas in HLB-symptomatic host plants.

scholarly journals Molecular signatures between citrus and Candidatus Liberibacter asiaticus

2021 ◽  
Vol 17 (12) ◽  
pp. e1010071
Author(s):  
Bin Hu ◽  
Muhammad Junaid Rao ◽  
Xiuxin Deng ◽  
Sheo Shankar Pandey ◽  
Connor Hendrich ◽  
...  
Keyword(s):  
Genomic Research ◽  
Molecular Signatures ◽  
Mechanistic Studies ◽  
Candidatus Liberibacter Asiaticus ◽  
Citrus Diseases ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Prevalent Strain ◽  
Liberibacter Asiaticus

Citrus Huanglongbing (HLB), also known as citrus greening, is one of the most devastating citrus diseases worldwide. Candidatus Liberibacter asiaticus (CLas) is the most prevalent strain associated with HLB, which is yet to be cultured in vitro. None of the commercial citrus cultivars are resistant to HLB. The pathosystem of Ca. Liberibacter is complex and remains a mystery. In this review, we focus on the recent progress in genomic research on the pathogen, the interaction of host and CLas, and the influence of CLas infection on the transcripts, proteins, and metabolism of the host. We have also focused on the identification of candidate genes for CLas pathogenicity or the improvements of HLB tolerance in citrus. In the end, we propose potentially promising areas for mechanistic studies of CLas pathogenicity, defense regulators, and genetic improvement for HLB tolerance/resistance in the future.

scholarly journals Lack of Evidence for Transmission of ‘Candidatus Liberibacter asiaticus’ Through Citrus Seed Taken from Affected Fruit

Plant Disease ◽  
2010 ◽  
Vol 94 (10) ◽  
pp. 1200-1205 ◽  
Author(s):  
John S. Hartung ◽  
Susan E. Halbert ◽  
Kirsten Pelz-Stelinski ◽  
Ronald H. Brlansky ◽  
Chunxian Chen ◽  
...  
Keyword(s):  
Expressed Sequence Tag ◽  
Zygotic Embryos ◽  
Candidatus Liberibacter Asiaticus ◽  
Repeated Testing ◽  
Citrus Industry ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus ◽  
Citrus Seed ◽  
Growth Habits

Citrus huanglongbing, putatively caused by the associated bacterium ‘Candidatus Liberibacter asiaticus’, is the greatest threat to the world citrus industry today. The bacterium is spread locally and regionally by the citrus psyllid Diaphorina citri, and also can be disseminated by propagation of contaminated scion budwood that is grafted to the appropriate rootstock. The planting of ‘Ca. Liberibacter asiaticus’-free trees is a component of a comprehensive strategy to manage huanglongbing. In contrast to the scion budwood, the rootstocks used to produce these trees are grown from seed. This research was undertaken to provide evidence as to whether or not ‘Ca. L. asiaticus’ can be transmitted through seed. Two groups of 360 or more seedlings each of various citrus species were grown from seed removed from fruit on trees that were symptomatic for huanglongbing and confirmed to be infected with ‘Ca. L. asiaticus’ by polymerase chain reaction (PCR) tests. These seedlings were tested multiple times over periods of up to 3 years. No symptoms typical of huanglongbing, such as blotchy leaf mottle, chlorotic shoots, or dieback of branches, were observed in these seedlings, and none of these 723 seedlings tested positive for the presence of ‘Ca. L. asiaticus’ even after repeated testing by sensitive quantitative PCR assays. Some sour orange seedlings did have quite pronounced and atypical growth, including stunting and mild to severe leaf malformation. These atypical growth habits were limited to seedlings that arose from zygotic embryos as determined by expressed-sequence tag simple-sequence repeat analyses. Thus, no evidence of transmission of ‘Ca. L. asiaticus’ via seed was obtained, and an earlier report of transmission of the pathogen through seed was not confirmed.

scholarly journals Chemical Compounds Effective Against the Citrus Huanglongbing Bacterium ‘Candidatus Liberibacter asiaticus’ In Planta

2011 ◽  
Vol 101 (9) ◽  
pp. 1097-1103 ◽  
Author(s):  
Muqing Zhang ◽  
Charles A. Powell ◽  
Lijuan Zhou ◽  
Zhenli He ◽  
Ed Stover ◽  
...  
Keyword(s):  
Test System ◽  
Candidatus Liberibacter Asiaticus ◽  
In Planta ◽  
Citrus Industry ◽  
Effective Level ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus ◽  
Trunk Injection ◽  
Therapeutic Compounds

Citrus Huanglongbing (HLB) is one of the most destructive diseases of citrus worldwide and is threatening the survival of the Floridian citrus industry. Currently, there is no established cure for this century-old and emerging disease. As a possible control strategy for citrus HLB, therapeutic compounds were screened using a propagation test system with ‘Candidatus Liberibacter asiaticus’-infected periwinkle and citrus plants. The results demonstrated that the combination of penicillin and streptomycin (PS) was effective in eliminating or suppressing the ‘Ca. L. asiaticus’ bacterium and provided a therapeutically effective level of control for a much longer period of time than when administering either antibiotic separately. When treated with the PS, ‘Ca. L. asiaticus’-infected periwinkle cuttings achieved 70% of regeneration rates versus <50% by other treatments. The ‘Ca. L. asiaticus’ bacterial titers in the infected periwinkle plants, as measured by quantitative real-time polymerase chain reaction, decreased significantly following root soaking or foliar spraying with PS. Application of the PS via trunk injection or root soaking also eliminated or suppressed the ‘Ca. L. asiaticus’ bacterium in the HLB-affected citrus plants. This may provide a useful tool for the management of citrus HLB and other Liberibacter-associated diseases.

scholarly journals Effect of Adjuvants on Oxytetracycline Uptake upon Foliar Application in Citrus

Antibiotics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 677
Author(s):  
Nabil Killiny ◽  
Faraj Hijaz ◽  
Pedro Gonzalez-Blanco ◽  
Shelley E. Jones ◽  
Myrtho O. Pierre ◽  
...  
Keyword(s):  
Foliar Application ◽  
Foliar Spray ◽  
Bacterial Pathogen ◽  
Water Addition ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus ◽  
Trunk Injection ◽  
Citrus Leaves ◽  
Target Effects

Recently in Florida, foliar treatments using products with the antibiotics oxytetracycline and streptomycin have been approved for the treatment of citrus Huanglongbing (HLB), which is caused by the putative bacterial pathogen ‘Candidatus Liberibacter asiaticus’. Herein, we assessed the levels of oxytetracycline and ‘Ca. L. asiaticus’ titers in citrus trees upon foliar applications with and without a variety of commercial penetrant adjuvants and upon trunk injection. The level of oxytetracycline in citrus leaves was measured using an oxytetracycline ELISA kit and ‘Ca. L. asiaticus’ titer was measured using quantitative PCR. Low levels of oxytetracycline were taken up by citrus leaves after foliar sprays of oxytetracycline in water. Addition of various adjuvants to the oxytetracycline solution showed minimal effects on its uptake by citrus leaves. The level of oxytetracycline in leaves from trunk-injected trees was higher than those treated with all foliar applications. The titer of ‘Ca. L. asiaticus’ in the midrib of leaves from trees receiving oxytetracycline by foliar application was not affected after four days and thirty days of application, whereas the titer was significantly reduced in oxytetracycline-injected trees thirty days after treatment. Investigation of citrus leaves using microscopy showed that they are covered by a thick lipidized cuticle. Perforation of citrus leaf cuticle with a laser significantly increased the uptake of oxytetracycline, decreasing the titer of ‘Ca. L. asiaticus’ in citrus leaves upon foliar application. Taken together, our findings indicate that trunk injection is more efficient than foliar spray even after the use of adjuvants. Our conclusion could help in setting useful recommendations for the application of oxytetracycline in citrus to improve tree health, minimize the amount of applied antibiotic, reduce environmental exposure, and limit off-target effects.

scholarly journals Viability of ‘Candidatus Liberibacter asiaticus’ Prolonged by Addition of Citrus Juice to Culture Medium

2014 ◽  
Vol 104 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Jennifer K. Parker ◽  
Sarah R. Wisotsky ◽  
Evan G. Johnson ◽  
Faraj M. Hijaz ◽  
Nabil Killiny ◽  
...  
Keyword(s):  
Grapefruit Juice ◽  
Culture Medium ◽  
Quantitative Polymerase Chain Reaction ◽  
Chemical Characterization ◽  
Candidatus Liberibacter Asiaticus ◽  
Citrus Greening Disease ◽  
Candidatus Liberibacter ◽  
The Media ◽  
Liberibacter Asiaticus

Huanglongbing, or citrus greening disease, is associated with infection by the phloem-limited bacterium ‘Candidatus Liberibacter asiaticus’. Infection with ‘Ca. L. asiaticus’ is incurable; therefore, knowledge regarding ‘Ca. L. asiaticus’ biology and pathogenesis is essential to develop a treatment. However, ‘Ca. L. asiaticus’ cannot currently be successfully cultured, limiting its study. To gain insight into the conditions conducive for growth of ‘Ca. L. asiaticus’ in vitro, ‘Ca. L. asiaticus’ inoculum obtained from seed of fruit from infected pomelo trees (Citrus maxima ‘Mato Buntan’) was added to different media, and cell viability was monitored for up to 2 months using quantitative polymerase chain reaction in conjunction with ethidium monoazide. Media tested included one-third King's B (K), K with 50% juice from the infected fruit, K with 50% commercially available grapefruit juice, and 100% commercially available grapefruit juice. Results show that juice-containing media dramatically prolong viability compared with K in experiments reproduced during 2 years using different juice sources. Furthermore, biofilm formed at the air–liquid interface of juice cultures contained ‘Ca. L. asiaticus’ cells, though next-generation sequencing indicated that other bacterial genera were predominant. Chemical characterization of the media was conducted to discuss possible factors sustaining ‘Ca. L. asiaticus’ viability in vitro, which will contribute to future development of a culture medium for ‘Ca. L. asiaticus’.

Highly sensitive and rapid detection of citrus Huanglongbing pathogen (Candidatus Liberibacter asiaticus) using Cas12a-based methods

2021 ◽  
Author(s):  
Matthew Wheatley ◽  
Yong-Ping Duan ◽  
Yinong Yang
Keyword(s):  
Early Detection ◽  
Nucleic Acids ◽  
Detection Sensitivity ◽  
Sensitive Detection ◽  
Detection Methods ◽  
Candidatus Liberibacter Asiaticus ◽  
Fluorescent Reporter ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus

Citrus Huanglongbing (HLB) or greening is one of the most devastating diseases of citrus worldwide. Sensitive detection of its causal agent, Candidatus Liberibacter asiaticus (CLas), is critical for early diagnosis and successful management of HLB. However, current nucleic acid-based detection methods are often insufficient for the early detection of CLas from asymptomatic tissue, and unsuitable for high-throughput and field-deployable diagnosis of HLB. Here we report the development of the Cas12a-based DETECTR (DNA endonuclease-targeted CRISPR trans reporter) assay for highly specific and sensitive detection of CLas nucleic acids from infected samples. The DETECTR assay, which targets the five-copy nrdB gene specific to CLas, couples isothermal amplification with Cas12a trans-cleavage of fluorescent reporter oligos and enables detection of CLas nucleic acids at the attomolar level. The DETECTR assay was capable of specifically detecting the presence of CLas across different infected citrus, periwinkle and psyllid samples, and shown to be compatible with lateral flow assay technology for potential field-deployable diagnosis. The improvements in detection sensitivity and flexibility of the DETECTR technology position the assay as a potentially suitable tool for early detection of CLas in infected regions.

scholarly journals Characterization of an ATP Translocase Identified in the Destructive Plant Pathogen “Candidatus Liberibacter asiaticus”

2009 ◽  
Vol 192 (3) ◽  
pp. 834-840 ◽  
Author(s):  
Cheryl M. Vahling ◽  
Yongping Duan ◽  
Hong Lin
Keyword(s):  
Plant Pathogen ◽  
Bioinformatic Analysis ◽  
Intracellular Bacteria ◽  
Cell Competition ◽  
Candidatus Liberibacter ◽  
Citrus Huanglongbing ◽  
Liberibacter Asiaticus ◽  
High Concentrations ◽  
Obligate Intracellular Bacteria

ABSTRACT ATP/ADP translocases transport ATP across a lipid bilayer, which is normally impermeable to this molecule due to its size and charge. These transport proteins appear to be unique to mitochondria, plant plastids, and obligate intracellular bacteria. All bacterial ATP/ADP translocases characterized thus far have been found in endosymbionts of protozoa or pathogens of higher-order animals, including humans. A putative ATP/ADP translocase was uncovered during the genomic sequencing of the intracellular plant pathogen “Candidatus Liberibacter asiaticus,” the causal agent of citrus huanglongbing. Bioinformatic analysis of the protein revealed 12 transmembrane helices and predicted an isoelectric point of 9.4, both of which are characteristic of this family of proteins. The “Ca. Liberibacter asiaticus” gene (nttA) encoding the translocase was subsequently expressed in Escherichia coli and shown to enable E. coli to import ATP directly into the cell. Competition assays with the heterologous E. coli system demonstrated that the translocase was highly specific for ATP and ADP but that other nucleotides, if present in high concentrations, could also be taken up and/or block the ability of the translocase to import ATP. In addition, a protein homologous to NttA was identified in “Ca. Liberibacter solanacearum,” the bacterium associated with potato zebra chip disease. This is the first reported characterization of an ATP translocase from “Ca. Liberibacter asiaticus,” indicating that some intracellular bacteria of plants also have the potential to import ATP directly from their environment.

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