Publications

4467

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.

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.

Bamboo is used for making structures, furniture, handicrafts, and ropes, as well as a source of food in the Philippines. One of the emerging diseases of bamboo in the country is the bamboo witches’ broom (BWB), which has been occasionally noted in three genera of bamboo – including Dendrocalamus, Gigantochloa, and Schizostachyum from various provinces in the Philippines (Ilocos Norte, Laguna, Batangas, Quezon, Agusan del Sur, Bukidnon, and South Cotabato) since the 1990s. However, studies and information about BWB in the country remain lacking and largely unexplored. In this study, we report a similar disease affecting Dendrocalamus and Gigantochloa bamboo species from Bohol and Davao and – for the first time – in Dendrocalamus merrillianus ("bayog") and Bambusa spinosa ("kawayan-tinik") from Isabela and Nueva Vizcaya. As a result of the surveys conducted from 1999–2019, the disease is now identified in six species across four genera of bamboo – namely, Gigantochloa spp. (G. levis and G. atter), Dendrocalamus spp. (D. asper and D. merrillianus), Schizostachyum lumampao, and Bambusa spinosa recorded in 11 provinces in the Philippines. The BWB symptoms include clustering of leaves forming a rosette-like structure, leaf proliferation, excessive limb formation from a single node, and shortening of internodes. Nested PCR using the universal primers P1/P7 and R16MF2/R1 targeting the phytoplasma 16S ribosomal RNA gene revealed positive amplification in five symptomatic BWB samples from Isabela, Philippines. Subsequent sequencing (~ 1.3kbp) and phylogenetic analysis using the representative BWB isolates from Isabela revealed > 98.65% genetic similarity and clustering to Candidatus Phytoplasma luffae, which belongs to the 16SrVIII group (Loofah Witches’ Broom Group). This paper determined the distribution of BWB in different species of bamboo in the Philippines, as well as the association of 'Ca. Phytoplasma luffae'-related strain (16SrVIII) to BWB.

AbstractBACKGROUNDCorn is one of the main crops grown globally to produce food for human consumption and animal feed, including raw materials for bioenergy. Effective pest management is critical for the economic viability of corn production. The leafhopper Dalbulus maidis and the diseases transmitted by it have become relevant to corn production. Our study aimed to determine environmental parameters that affect D. maidis populations and the impacts of pathogen dispersion on corn productivity under different rotation systems and sowing seasons.RESULTSThe population density of leafhoppers found in the studied crops was low but capable of establishing the diseases and spreading them widely in the crops. The leafhopper's highest occurrence was in the corn vegetative development stage, and its population peaks were earlier in the corn off‐season. The incidence of maize rayado fino virus and maize bushy stunt phytoplasma were higher in corn off‐season than in the growing season. The incidence of diseases was higher in the final stages of the cultivation cycle. Yield losses were significantly higher for maize bushy stunt phytoplasma and not significant for maize rayado fino virus.CONCLUSIONOur study observed that corn's physiological stage was the main factor influencing D. maidis dynamics. The occurrence of D. maidis at low densities was sufficient to ensure the efficient transmission and dissemination of maize rayado fino virus and maize bushy stunt phytoplasma, which had a higher incidence in the reproductive stage and the corn sowed off‐season. © 2023 Society of Chemical Industry.