Publications

3867

AbstractAsian citrus psyllid (Diaphorina citri, D. citri) is the important vector of “Candidatus Liberibacter asiaticus” (CLas), associated with Huanglongbing, the most devastating citrus disease worldwide. CLas can affect endosymbiont abundance of D. citri. Here, we generated the high-quality gut endosymbiont metagenomes of Diaphorina citri on the condition of CLas infected and uninfected. The dataset comprised 6616.74 M and 6586.04 M raw reads, on overage, from CLas uninfected and infected psyllid strains, respectively. Taxonomic analysis revealed that a total of 1046 species were annotated with 10 Archaea, 733 Bacteria, 234 Eukaryota, and 69 Viruses. 80 unique genera in CLas infected D. citri were identified. DIAMOND software was used for complement function research against various functional databases, including Nr, KEGG, eggNOG, and CAZy, which annotated 84543 protein-coding genes. These datasets provided an avenue for further study of the interaction mechanism between CLas and D. citri.

“Bois noir” disease associated with ‘Candidatus Phytoplasma solani’ seriously compromises the production and survival of grapevines (Vitis vinifera L.) in Europe. Understanding the plant response to phytoplasmas should help to improve disease control strategies. Using a combined metabolomic and transcriptomic analysis, this work, therefore, investigated the phytoplasma–grapevine interaction in red cultivar Sangiovese in a vineyard over four seasonal growth stages (from late spring to late summer), comparing leaves from healthy and infected grapevines (symptomatic and symptomless). We found an accumulation of both conjugate and free salicylic acids (SAs) in the leaves of ‘Ca. P. solani’-positive plants from early stages of infection, when plants are still asymptomatic. A strong accumulation of gentisic acid (GA) associated with symptoms progression was found for the first time. A detailed analysis of phenylpropanoids revealed a significant accumulation of hydroxycinnamic acids, flavonols, flavan 3-ols, and anthocyanin cyanidin 3-O-glucoside, which are extensively studied due to their involvement in the plant response to various pathogens. Metabolomic data corroborated by gene expression analysis indicated that phenylpropanoid biosynthetic and salicylic acid-responsive genes were upregulated in ‘Ca. P. solani-positive plants compared to -negative ones during the observed period.

Psyllid yellows, vein-greening (VG), and zebra chip (ZC) diseases, which are primarily transmitted by potato psyllid (PoP) carrying Candidatus Liberibacter solanacearum (CLso), have caused significant losses in solanaceous crop production worldwide. Pathogens interact with their vectors at the organic and cellular levels, while the potential changes that may occur at the biochemical level are less well reported. In this study, the impact of CLso on the metabolism of PoP and the identification of biomarkers from infected psyllids were examined. Using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) analysis, metabolomic changes in CLso-infected psyllids were compared to uninfected ones. A total of 34 metabolites were identified as potential biomarkers of CLso infection, which were primarily related to amino acid, carbohydrate, and lipid metabolism. The significant increase in glycerophospholipids is thought to be associated with CLso evading the insect vector’s immune defense. Matrix-assisted Laser Desorption Ionization Mass Spectrometry Imaging (MALDI-MSI) was used to map the spatial distribution of these biomarkers, revealing that 15-keto-Prostaglandin E2 and alpha-D-Glucose were highly expressed in the abdomen of uninfected psyllids but down-regulated in infected psyllids. It is speculated that this down-regulation may be due to CLso evading surveillance by immune suppression in the PoP midgut. Overall, valuable biochemical information was provided, a theoretical basis for a better understanding of psyllid-pathogen interactions was offered, and the findings may aid in breaking the transmission cycle of these diseases.

Huanglongbing (HLB), caused by the Candidatus Liberibacter spp., is the most devastating disease in the citrus industry. HLB significantly affects and alters the microbial community structure or potential function of the microbial community of leaves and roots. However, it is unknown how the microbial community structure of the pericarp with different pigments is affected by Candidatus Liberibacter asiaticus (CLas). This study identified the enriched taxa of the microbial community in the citrus pericarp with normal or abnormal pigment and determine the effects of HLB on the pericarp microbial community using 16S rRNA-seq. The alpha and beta diversity and composition of microbial communities were significantly different between normal and abnormal pigment pericarp tissues of ripe fruits infected by CLas. Firmicutes, Actinobacteriota, Bacteroidota, Acidobacteriota, and Desulfobacterota dominated the pericarp microbiota composition in WDYFs (whole dark yellow fruits) samples. The relative abundance of most genera in WDYFs was higher than 1%, such as Burkholderia, and Pelomonas. However, with the exception of the HLB pathogen, the relative abundance of most genera in the abnormal-colored pericarp samples was less than 1%. CLas decreased the relative abundance of pericarp taxonomic. The predicted function of microbial was more plentiful and functional properties in the WDYF sample, such as translation, ribosomal structure and biogenesis, amino acid transport and metabolism, energy production and conversion, and some other clusters of orthologous groups (COG) except for cell motility. The results of this study offer novel insights into understanding the composition of microbial communities of the CLas-affected citrus pericarps and contribute to the development of biological control strategies for citrus against Huanglongbing.

AbstractDuring the past two decades, a high mortality of coconut palms was observed in the coastal areas of Equatorial Guinea. Reportedly, the palm population has been reduced by 60%–70%, and coconut production has decreased accordingly. To identify the cause of the mortality, a survey was carried out in April 2021 in various localities of the coconut belt. Molecular analyses carried out on 16S rRNA and secA genes detected phytoplasma presence in the majority of the samples. Sequencing and BLAST search of the 16S rRNA gene sequences showed >99% identity of the detected phytoplasmas to ‘Candidatus Phytoplasma palmicola’. The RFLP analyses of 16S ribosomal gene using Tru1I and TaqI enzymes led to assign these phytoplasmas to subgroup 16SrXXII‐A. In all samples that tested positive, including one from a hybrid coconut palm and two from oil palm the same phytoplasma was identified. The phylogenetic analyses of 16S rRNA and secA genes confirmed respectively 99.98%–100% and 97.94%–100% identity to ‘Ca. P. palmicola’. RFLP analyses using MboII enzyme on the secA gene amplicon differentiated the phytoplasma found in Equatorial Guinea from those present in Ghana and Ivory Coast. The Equatorial Guinean phytoplasma strain resulted to be identical to the strains from Mozambique, confirming the presence of a geographic differentiation among phytoplasma strains in the coastal areas of Western and Central Africa. The identified phytoplasma is different from the ‘Ca. P. palmicola’ strains found in Ghana and Ivory Coast and represents the first identification a 16SrXXII‐A strain in Equatorial Guinea and in Central Africa. Strict monitoring and surveillance procedures for early detection of the pathogen are strongly recommended to reduce its impact and further spread in the country and permit the recovery of coconut plantations.

AbstractCandidatusLiberibacter asiaticus (CLas) is the causal agent of the devastating citrus Huanglongbing (HLB) disease. Our understanding of the pathogenicity mechanism and biology of CLas remain limited because CLas has not been cultured in artificial media. CLas encodes 1136 proteins of which 415 have unknown functions. Since genetic studies of CLas genes with unknown functions are impossible, we utilized genome-wide protein-protein interactions (PPIs) yeast-two-hybrid (Y2H) assays to help solve the mystery. PPIs are fundamental to all cellular processes and machinery and instrumental in investigating uncharacterized proteins and inferring biological pathways. In total, 916 bait and 936 prey proteins were included in the three-phase screening, which identified 4245 interactions. The false positive rate of the Y2H assay was estimated to be 3.1%. Pull-down assays confirmed the robustness of our Y2H. The average interactions per node for CLas Y2H interactome were approximately 15.6, significantly higher than free-living bacteria, indicating genome reduction has led to a multi-function of proteins. PPIs provide clues for functions of 371 uncharacterized proteins of CLas. Forty HUB node proteins were identified which might play critical roles in CLas, including a quinone oxidoreductase and LysR that are known to protect bacteria against oxidative stress. This explains why CLas survives well in the phloem even though it triggers immune-mediated disease, systemic and chronic production of reactive oxygen species, and phloem cell death. This PPI database facilitates the investigation of CLas cellular biochemistry and physiology, functions of uncharacterized proteins, and pathogenicity mechanisms of the pathogen.

Abstract Objectives: “Candidatus Liberibacter asiaticus” (CLas) is an un-culturable α-proteobacterium that caused citrus Huanglongbing (HLB), a destructive disease threatening citrus production worldwide. In China, the presence of HLB was first reported in Chaoshan region of Guangdong province, China around a century ago. Thus, whole genome information of CLas strains from Chaoshan area become the most important resource to understand the population diversity and evaluation of CLas in China. Data description: CLas strain GDCZ was originally from Chaozhou city (Chaoshan area) and sequenced using Pacbio Sequel long-read sequencing and Illumina short-read sequencing. The genome of strain GDCZ comprised of 1,230,507 bp with an average G+C content of 36.4%, along with a circular CLasMV1 phage: CLasMV1_GDCZ (8,869 bp). The CLas strain GDCZ contained a Type 2 prophage (37,452 bp) and encoded a total of 1,057 open reading frames and 53 RNA genes. The whole genome sequence of CLas strain GDCZ from the historical HLB endemic region in China will serve as a useful resource for further analyses of CLas evolution and HLB epidemiology in China and world.