Annotation of glycolysis, gluconeogenesis, and trehaloneogenesis pathways provide insight into carbohydrate metabolism in the Asian citrus psyllid

Citrus greening disease is caused by the pathogen Candidatus Liberibacter asiaticus, which is transmitted by the Asian citrus psyllid, Diaphorina citri. There is no curative treatment or significant prevention mechanism for this detrimental disease that causes continued economic losses from reduced citrus production. A high quality genome of D. citri is being manually annotated to provide accurate gene models required to identify novel control targets and increase understanding of this pest. Here, we annotated genes involved in glycolysis, gluconeogenesis, and trehaloneogenesis in the D. citri genome, as these are core metabolic pathways and suppression could reduce this pest. Specifically, twenty-five genes were identified and annotated in the glycolysis and gluconeogenesis pathways and seven genes for the trehaloneogenesis pathway. Comparative analysis showed that the glycolysis genes in D. citri are highly conserved compared to orthologs in other insect systems, but copy numbers vary in D. citri. Expression levels of the annotated gene models were analyzed and several enzymes in the glycolysis pathway showed high expression in the thorax. This is consistent with the primary use of glucose by flight muscles located in the thorax. A few of the genes annotated in D. citri have been targeted for gene knockdown as a proof of concept, for RNAi therapeutics. Thus, manual annotation of these core metabolic pathways provides accurate genomic foundations for developing gene-targeting therapeutics to reduce D. citri.

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Citrus Huanglongbing: A Newly Relevant Disease Presents Unprecedented Challenges

Phytopathology ◽

10.1094/phyto-12-12-0331-rvw ◽

2013 ◽

Vol 103 (7) ◽

pp. 652-665 ◽

Cited By ~ 170

Author(s):

Nian Wang ◽

Pankaj Trivedi

Keyword(s):

Pathogenic Bacteria ◽

Management Strategies ◽

Economic Losses ◽

Citrus Industry ◽

Efficient Management ◽

Citrus Diseases ◽

Citrus Production ◽

Candidatus Liberibacter ◽

Citrus Huanglongbing ◽

Ecological Importance

Citrus huanglongbing (HLB) is one of the oldest citrus diseases and has been known for over a century. HLB is caused by ‘Candidatus Liberibacter’ spp. that are phloem-limited, fastidious α-proteobacteria and infect hosts in different Kingdoms (i.e., Animalia and Plantae). When compared with well-characterized, cultivatable plant-pathogenic Gram-negative bacteria, the interactions of uncultured insect-vectored plant-pathogenic bacteria, including ‘Ca. Liberibacter’ spp., with their hosts remain poorly understood. ‘Ca. Liberibacter’ spp. have been known to cause HLB, which has been rapidly spreading worldwide, resulting in dramatic economic losses. HLB presents an unprecedented challenge to citrus production. In this review, we focus on the most recent research on citrus, ‘Candidatus Liberibacter asiaticus’, and psyllid interactions, specifically considering the following topics: evolutionary relationships among ‘Ca. Liberibacter’ spp., genetic diversity, host range, genome analysis, transmission, virulence mechanisms, and the ecological importance of HLB. Currently, no efficient management strategy is available to control HLB, although some promising progress has been made. Further studies are needed to understand citrus, ‘Ca. L. asiaticus’, and psyllid interactions to design innovative management strategies. Although HLB has been problematic for over a century, we can only win the battle against HLB with a coordinated and deliberate effort by the citrus industry, citrus growers, researchers, legislatures, and governments.

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Identification and Characterization of the Huanglongbing Bacterium in Pummelo from Multiple Locations in Guangdong, P. R. China

Plant Disease ◽

10.1094/pdis-92-4-0513 ◽

2008 ◽

Vol 92 (4) ◽

pp. 513-518 ◽

Cited By ~ 23

Author(s):

X. Deng ◽

J. Chen ◽

Z. Feng ◽

Z. Shan ◽

H. Guo ◽

...

Keyword(s):

Sweet Orange ◽

Nucleotide Polymorphisms ◽

Sequence Comparisons ◽

Research Attention ◽

Republic Of China ◽

Citrus Greening Disease ◽

Citrus Production ◽

History Of ◽

Candidatus Liberibacter ◽

Liberibacter Asiaticus

Huanglongbing (HLB, yellow shoot disease, ex. citrus greening disease), caused by Candidatus Liberibacter spp., is highly destructive to citrus production in Asia, Africa, and South America. Although primarily affecting sweet orange and mandarin, HLB has long been observed in pummelo in Guangdong Province, People's Republic of China; however, the disease in pummelo has received little research attention. Accordingly, it remains unclear how closely related the strains of Ca. Liberibacter in pummelo are to those in other citrus species. In this study, the loci of 16S rDNA, rplAJ (β-operon of ribosomal protein), and an outer membrane protein (omp) gene were analyzed and characterized among strains of Ca. Liberibacter in pummelo samples from six different locations in Guangdong. Sequence comparisons indicated that ‘Candidatus Liberibacter asiaticus’, but not ‘Ca. Liberibacter africanus’ or ‘Ca. Liberibacter americanus’, was exclusively associated with HLB symptoms in pummelo. The pummelo strains of ‘Ca. Liberibacter asiaticus’ from Guangdong were highly homogeneous. Analyses of single-nucleotide polymorphisms in the omp locus showed that the Guangdong pummelo strains grouped with ‘Ca. Liberibacter asiaticus’ strains from Thailand, Nepal, and an unspecified location in China but differed from the Philippine and China-Behai strains. Based on the sequence homogeneity at the omp locus, the history of pummelo culture and the means by which HLB is known to be spread, we believe that, likely, the pummelo strain of ‘Ca. Liberibacter asiaticus’ recently was spread to pummelo in the study areas from infected sweet orange or mandarin trees by insect vectors or by propagation of pummelo infected elsewhere.

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Understanding Citrus Greening Disease and Its Possible Management Strategies in Nepal

International Journal of Applied Sciences and Biotechnology ◽

10.3126/ijasbt.v9i4.40805 ◽

2021 ◽

Vol 9 (4) ◽

pp. 227-234

Author(s):

Sameer Pokhrel ◽

Swikriti Pandey ◽

Ashish Ghimire ◽

Savyata Kandel

Keyword(s):

Management Strategies ◽

Citrus Greening ◽

Insect Vector ◽

Candidatus Liberibacter Asiaticus ◽

Citrus Greening Disease ◽

The World ◽

Citrus Production ◽

Candidatus Liberibacter ◽

Liberibacter Asiaticus ◽

Citrus Orchards

Huanglongbing (HLB), also known as citrus greening, is a devastating disease of citrus that has decimated several citrus orchards throughout the world. The disease is associated with three species of unculturable and phloem-limited bacteriae, Candidatus Liberibacter asiaticus, Candidatus Liberibacter africanus and Candidatus Liberibacter americanus. The most common species of bacteria found in Nepal is Candidatus Liberibacter asiaticus which is transmitted by an insect vector, Asian citrus psyllid (Diaphorina citri). This disease has been detected in several economically important citrus production areas of Nepal, which resulted in heavy yield loss. No cure for the disease has been discovered yet and it is essential to practice proper management strategies to maintain citrus health and sustain citrus production under HLB pressure. Several disease management approaches such as pathogen-free nursery establishment, use of disease tolerant rootstock cultivars, proper irrigation and nutrient supply, removal of HLB affected trees, and control of psyllid with frequent insecticide application are widely practiced throughout the world. This review article highlights the characteristics of the citrus greening disease and its insect vector and gives insights into their management techniques. Several technologically advanced options available to minimize the HLB infection might not be feasible currently in Nepal due to economic and topographic constraints. This article also aims to bring into focus the cost-effective methods that growers in Nepal can practice to mitigate the impact of HLB disease in their citrus orchards. Int. J. Appl. Sci. Biotechnol. Vol 9(4): 227-238.

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Revisiting the Complex Pathosystem of Huanglongbing: Deciphering the Role of Citrus Metabolites in Symptom Development

Metabolites ◽

10.3390/metabo10100409 ◽

2020 ◽

Vol 10 (10) ◽

pp. 409

Author(s):

Yasser Nehela ◽

Nabil Killiny

Keyword(s):

Metabolic Pathways ◽

Defense Responses ◽

Symptom Development ◽

Bacterial Diseases ◽

Citrus Greening Disease ◽

History Of ◽

Candidatus Liberibacter ◽

Nutritional Needs ◽

Liberibacter Asiaticus ◽

Host Metabolism

Huanglongbing (HLB), formerly known as citrus greening disease, is one of the most devastating bacterial diseases in citrus worldwide. HLB is caused by ‘Candidatus Liberibacter asiaticus’ bacterium and transmitted by Diaphorina citri. Both ‘Ca. L. asiaticus’ and its vector manipulate the host metabolism to fulfill their nutritional needs and/or to neutralize the host defense responses. Herein, we discuss the history of HLB and the complexity of its pathosystem as well as the geographical distribution of its pathogens and vectors. Recently, our recognition of physiological events associated with ‘Ca. L. asiaticus’ infection and/or D. citri-infestation has greatly improved. However, the roles of citrus metabolites in the development of HLB symptoms are still unclear. We believe that symptom development of HLB disease is a complicated process and relies on a multilayered metabolic network which is mainly regulated by phytohormones. Citrus metabolites play vital roles in the development of HLB symptoms through the modulation of carbohydrate metabolism, phytohormone homeostasis, antioxidant pathways, or via the interaction with other metabolic pathways, particularly involving amino acids, leaf pigments, and polyamines. Understanding how ‘Ca. L. asiaticus’ and its vector, D. citri, affect the metabolic pathways of their host is critical for developing novel, sustainable strategies for HLB management.

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Update on Huanglongbing Progression and Current Research in Florida

ASME 2009 Citrus Engineering Conference ◽

10.1115/cec2009-5501 ◽

2009 ◽

Author(s):

R. H. Brlansky

Keyword(s):

Management Strategies ◽

Causal Agent ◽

Detection Methods ◽

Citrus Greening Disease ◽

Deficiency Symptoms ◽

Cultivar Development ◽

Citrus Production ◽

Candidatus Liberibacter ◽

Citrus Huanglongbing ◽

Causal Bacterium

Citrus Huanglongbing (HLB) or citrus greening disease has been in Florida since at least 2005 and has spread to all of the citrus producing regions. The Asian citrus psyllid (Diaphorina citri) is the insect that transmits the suspected causal bacterium which is tentatively named Candidatus Liberibacter asiaticus. Symptoms of the disease are first the yellow shoot (huanglongbing) and the development of the blotchy mottle symptom in the leaves. Mineral deficiency symptoms are often found on infected trees and may mimic normal deficiency symptoms. Fruit on infected trees may be small and lopsided and may abscise prematurely and therefore productivity is reduced. Tree decline eventually occurs. The suspected causal bacterium has not been obtained in pure culture and a polymerase chain reaction (PCR) test along with symptoms, is the only way to verify infected trees. All citrus cultivars appear susceptible. Current management strategies are chemical and biological control to reduced psyllid populations, inspections for infected trees and removal of infected trees to reduce the available pathogen inoculum. Current research on psyllid control, psyllid transmission, symptomology, detection, culturing the causal agent, development of new detection methods, alternative hosts of the psyllid and the causal agent, physiology of the disease, resistant or tolerant cultivar development and more is discussed. HLB is a major problem for citrus production and often limits commercial production. Paper published with permission.

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African Citrus Greening Disease in East Africa: Incidence, Severity, and Distribution Patterns

Journal of Economic Entomology ◽

10.1093/jee/toz167 ◽

2019 ◽

Vol 112 (5) ◽

pp. 2389-2397 ◽

Cited By ~ 4

Author(s):

B A Rasowo ◽

F M Khamis ◽

S A Mohamed ◽

I J Ajene ◽

O F Aidoo ◽

...

Keyword(s):

East Africa ◽

Distribution Patterns ◽

Causal Agent ◽

Citrus Greening ◽

Citrus Greening Disease ◽

Early Disease Detection ◽

Molecular Phylogenetic ◽

Citrus Production ◽

Candidatus Liberibacter ◽

Greening Disease

Abstract African citrus greening disease (ACGD) is considered as one of the major diseases of citrus threatening citrus production in East Africa. Our study aimed for the first time to assess the incidence, severity, and distribution patterns of ACGD in Kenya and Tanzania. In total, 105 citrus orchards were assessed in 13 regions representing low, mid, and high altitude areas. In each backyard and orchard, trees were randomly selected and rated for visual ACGD symptoms; then leaves and insect samples collected for analysis of ‘Candidatus Liberibacter africanus’ (CLaf), the presumptive causal agent of ACGD. Endpoint PCR, sequencing, and molecular phylogenetic tools were employed to confirm the identity of potential circulating pathogens. Incidence and severity of ACGD varied significantly among the different regions. Both Trioza erytreae (Del Guerico) (Hemiptera: Triozidae) and the invasive Asian citrus psyllid vector Diaphorina citri (Kuwayama) (Hemiptera: Liviidae) were found to co-occur in upper and lower midland regions. Molecular characterization identified ‘Candidatus Liberibacter africanus spp. Clausenae’ (CLafCl) as the main causal agent of ACGD in most of the citrus plants and insect samples. No instances of Candidatus Liberibacter asiaticus infection were found. These findings provide valuable insights into understanding and management of ACGD by employing stringent and early disease detection tools to curb the spread of the disease.

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Technological Advances in Huanglongbing (HLB) or Citrus Greening Disease Management

Journal of Nepal Agricultural Research Council ◽

10.3126/jnarc.v1i0.15735 ◽

2016 ◽

Vol 1 ◽

pp. 41-50 ◽

Cited By ~ 2

Author(s):

Krishna Prasad Paudyal

Keyword(s):

Agricultural Research ◽

Management Strategies ◽

Economic Loss ◽

Citrus Greening ◽

Economic Losses ◽

Detection Techniques ◽

Citrus Greening Disease ◽

The World ◽

Candidatus Liberibacter ◽

Greening Disease

Huanglongbing (HLB), previously citrus greening disease, is the most destructive of citrus species causing major threat to the world citrus industry. The disease was reported from China in 1919 and now known to occur in more than 40 different countries of Asia, Africa, South and North America. Three species of gram negative bacterium namely Candidatus Liberibacter asiaticus, Candidatus Liberibacter africanus and Candidatus Liberibacter americanus are the casual organisms of HLB, respectively prevailing in the continent of Asia, Africa and South America. It is one of the most extensively researched subjects in citriculture world. HLB was detected in 2004 and 2005, respectively in San Paulo of Brazil and Florida of USA: the two leading citrus production hub of the world causing huge economic loss within 5 years of first detection. Since then research on HLB detection and management was further accelerated in American continents. This paper presents the scientific advancement made on detection, spread, economic losses caused by HLB in different parts of the world and controlling management strategies. Remarkable achievements have been made on HLB detection techniques including iodine test, qPCR and more recently in spectroscopy. While efforts are being made to develop resistance varieties using conventional and biotechnological tools management strategy which includes reduction of inoculums source, vector control and replant with disease-free planting materials still remains major option for HLB control. Citrus intercropping with guava have shown promising results for vector reduction.Journal of Nepal Agricultural Research Council Vol.1 2015, pp.41-50

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2006 Florida Citrus Pest Management Guide: Huanglongbing (Citrus Greening)

EDIS ◽

10.32473/edis-cg086-2005 ◽

2019 ◽

Vol 2006 (1) ◽

Author(s):

Ronald H. Brlansky ◽

Kuang-Ren Chung ◽

Michael E. Rogers

Keyword(s):

Citrus Greening ◽

Rapid Decline ◽

Publication Date ◽

Citrus Greening Disease ◽

Bright Yellow ◽

Citrus Production ◽

Candidatus Liberibacter ◽

Greening Disease ◽

Florida Citrus ◽

Serious Disease

Huanglongbing (HLB), commonly called citrus greening disease, is caused by the bacterium, Candidatus Liberibacter spp. The name huanglongbing means “yellow dragon” which describes the symptom of a bright yellow shoot that commonly occurs on a sector of infected trees. HLB is a serious disease of citrus because it affects all citrus cultivars and causes rapid decline of trees. This document is PP-225, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date November 2005. PP-225/CG086: 2020–2021 Florida Citrus Production Guide: Huanglongbing (Citrus Greening) (ufl.edu)

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Detection of Asian Citrus Psyllid (Hemiptera: Psyllidae) in Ethiopia: A New Haplotype and its Implication to the Proliferation of Huanglongbing

Journal of Economic Entomology ◽

10.1093/jee/toaa113 ◽

2020 ◽

Vol 113 (4) ◽

pp. 1640-1647 ◽

Cited By ~ 2

Author(s):

Inusa J Ajene ◽

Fathiya Khamis ◽

Shifa Ballo ◽

Gerhard Pietersen ◽

Barbara van Asch ◽

...

Keyword(s):

Likelihood Method ◽

Coi Gene ◽

Asian Citrus Psyllid ◽

Diaphorina Citri ◽

Candidatus Liberibacter Asiaticus ◽

Citrus Greening Disease ◽

Candidatus Liberibacter ◽

Liberibacter Asiaticus ◽

Mitochondrial Cytochrome Oxidase ◽

Causal Bacterium

Abstract Diaphorina citri Kuwayama, also known as the Asian citrus psyllid, is a pest of citrus known for its transmission of Candidatus Liberibacter asiaticus (Ca. L. asiaticus), the causal bacterium of Huanglongbing. The African citrus triozid Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) has been the putative vector of Candidatus Liberibacter africanus (Ca. L. africanus) which causes the African citrus greening disease, until the recent detection of D. citri on the continent. Following reports of D. citri in Kenya and Tanzania, we surveyed citrus plants to establish the presence/absence of D. citri in Ethiopia in citrus-growing regions ranging from 900 to 2,460 m above sea level (masl). Diaphorina citri adults were detected in five of the surveyed sites in Ethiopia. Adult insects encountered were collected using an aspirator and stored in 97% ethanol. The mitochondrial cytochrome oxidase 1 (mt COI) gene of the collected insects was amplified using LepF1/LepR1 primers, and sequences obtained showed low variation, which fell within the acceptable range of species. BLAST was used to query the sequences obtained, and all the sequences linked to D. citri accessions that are available in GenBank. The analysis of the sequences revealed a new haplotype of the species that differs from haplotypes previously reported. Phylogenetic relationships of our samples and other D. citri reference sequences was inferred using the Maximum-likelihood method. Monophyly was observed between the samples and the publicly available sequences from global accessions. This is the first report of the presence of D. citri in Ethiopia.

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Improved annotation of the insect vector of Citrus greening disease: Biocuration by a diverse genomics community

10.1101/099168 ◽

2017 ◽

Cited By ~ 1

Author(s):

Surya Saha ◽

Prashant S Hosmani ◽

Krystal Villalobos-Ayala ◽

Sherry Miller ◽

Teresa Shippy ◽

...

Keyword(s):

Draft Genome ◽

Gene Families ◽

Citrus Greening ◽

Asian Citrus Psyllid ◽

Clear Understanding ◽

Insect Vector ◽

Training Experience ◽

Citrus Greening Disease ◽

Greening Disease ◽

Gene Models

ABSTRACTThe Asian citrus psyllid (Diaphorina citri Kuwayama) is the insect vector of the bacterium Candidatus Liberibacter asiaticus (CLas), the pathogen associated with citrus Huanglongbing (HLB, citrus greening). HLB threatens citrus production worldwide. Suppression or reduction of the insect vector using chemical insecticides has been the primary method to inhibit the spread of citrus greening disease. Accurate structural and functional annotation of the Asian citrus psyllid genome, as well as a clear understanding of the interactions between the insect and CLas, are required for development of new molecular-based HLB control methods. A draft assembly of the D. citri genome has been generated and annotated with automated pipelines. However, knowledge transfer from well-curated reference genomes such as that of Drosophila melanogaster to newly sequenced ones is challenging due to the complexity and diversity of insect genomes. To identify and improve gene models as potential targets for pest control, we manually curated several gene families with a focus on genes that have key functional roles in D. citri biology and CLas interactions. This community effort produced 530 manually curated gene models across developmental, physiological, RNAi regulatory, and immunity-related pathways. As previously shown in the pea aphid, RNAi machinery genes putatively involved in the microRNA pathway have been specifically duplicated. A comprehensive transcriptome enabled us to identify a number of gene families that are either missing or misassembled in the draft genome. In order to develop biocuration as a training experience, we included undergraduate and graduate students from multiple institutions, as well as experienced annotators from the insect genomics research community. The resulting gene set (OGS v1.0) combines both automatically predicted and manually curated gene models. All data are available on https://citrusgreening.org/.

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