Occurrence and genetic characterization of Enterocytozoon bieneusi in pet dogs in Yunnan Province, China.

Enterocytozoon bieneusi is the most common microsporidian species in humans and can affect over 200 animal species. Considering possible increasing risk of human E. bieneusi infection due to close contact with pet dogs and identification of zoonotic E. bieneusi genotypes, 589 fresh fecal specimens of pet dogs were collected from Yunnan Province, China to determine the occurrence of E. bieneusi, characterize dog-derived E. bieneusi isolates, and assess their zoonotic potential at the genotype level. Enterocytozoon bieneusi was identified and genotyped by PCR and sequencing of the internal transcribed spacer (ITS) region of the ribosomal RNA (rRNA) gene. Twenty-nine specimens (4.9%) were positive. A statistical difference was observed in occurrence rates of E. bieneusi in pet dogs among 11 sampling sites by Fisher's exact test. Fifteen genotypes were identified and all of them phylogenetically belonged to zoonotic group 1, including four known genotypes (EbpC, D, Peru 8, and Henan-III) and 11 novel genotypes. Genotype Henan-III was reported in dogs for the first time. The finding of known genotypes found previously in humans and novel genotypes falling into zoonotic group 1 indicates that dogs may play a role in the transmission of E. bieneusi to humans in the investigated areas.

Title: Occurrence et caractérisation génétique d'Enterocytozoon bieneusi chez les chiens de compagnie dans la province du Yunnan, Chine. Abstract: Enterocytozoon bieneusi est l'espèce de microsporidies la plus répandue chez l'homme et peut affecter plus de 200 espèces animales. Compte tenu du risque accru possible d'infection humaine à E. bieneusi en raison d'un contact étroit avec des chiens de compagnie et de l'identification de génotypes zoonotiques d'E. bieneusi, 589 échantillons fécaux frais de chiens de compagnie ont été collectés dans la province du Yunnan, en Chine, pour déterminer la présence d'E. bieneusi, caractériser les isolats obtenus de chiens, et évaluer leur potentiel zoonotique au niveau du génotype. Enterocytozoon bieneusi a été identifié et génotypé par PCR et séquençage de la région d'espacement transcrit interne (ITS) du gène de l'ARN ribosomal (ARNr). Vingt-neuf échantillons (4,9%) étaient positifs. Une différence statistique a été observée dans les taux de présence d'E. bieneusi chez les chiens de compagnie parmi 11 sites d'échantillonnage par le test exact de Fisher. Quinze génotypes ont été identifiés et tous appartenaient phylogénétiquement au groupe zoonotique 1, dont quatre génotypes connus (EbpC, D, Peru 8 et Henan-III) et 11 nouveaux génotypes. Le génotype Henan-III est signalé pour la première fois chez le chien. La découverte de génotypes connus précédemment trouvés chez l'homme et de nouveaux génotypes appartenant au groupe zoonotique 1 indique que les chiens peuvent jouer un rôle dans la transmission d'E. bieneusi aux humains dans les zones étudiées.

Reversible phosphorylation of a lectin-receptor-like kinase controls xylem immunity.

Pattern-recognition receptors (PRRs) mediate basal resistance to most phytopathogens. However, plant responses can be cell type specific, and the mechanisms governing xylem immunity remain largely unknown. We show that the lectin-receptor-like kinase LORE contributes to xylem basal resistance in Arabidopsis upon infection with Ralstonia solanacearum, a destructive plant pathogen that colonizes the xylem to cause bacterial wilt. Following R. solanacearum infection, LORE is activated by phosphorylation at residue S761, initiating a phosphorelay that activates reactive oxygen species production and cell wall lignification. To prevent prolonged activation of immune signaling, LORE recruits and phosphorylates type 2C protein phosphatase LOPP, which dephosphorylates LORE and attenuates LORE-mediated xylem immunity to maintain immune homeostasis. A LOPP knockout confers resistance against bacterial wilt disease in Arabidopsis and tomatoes without impacting plant growth. Thus, our study reveals a regulatory mechanism in xylem immunity involving the reversible phosphorylation of receptor-like kinases.

Genome-Wide Identification of Ralstonia solanacearum Genes Required for Survival in Tomato Plants.

Ralstonia solanacearum is an extremely destructive phytopathogenic bacterium for which there is no effective control method. Though many pathogenic factors have been identified, the survival strategies of R. solanacearum in host plants remain unclear. Transposon insertion sequencing (Tn-seq) is a high-throughput genetic screening technology. This study conducted a Tn-seq analysis using the in planta environment as selective pressure to identify R. solanacearum genes required for survival in tomato plants. One hundred thirty genes were identified as putative genes required for survival in tomato plants. Sixty-three of these genes were classified into four Clusters of Orthologous Groups categories. The absence of genes that encode the outer membrane lipoprotein LolB (RS_RS01965) or the membrane protein RS_RS04475 severely decreased the in planta fitness of R. solanacearum. RS_RS09970 and RS_RS04490 are involved in tryptophan and serine biosynthesis, respectively. Mutants that lack RS_RS09970 or RS_RS04490 did not cause any wilt symptoms in susceptible tomato plants. These results confirmed the importance of genes related to "cell wall/membrane/envelope biogenesis" and "amino acid transport and metabolism" for survival in plants. The gene encoding NADH-quinone oxidoreductase subunit B (RS_RS10340) is one of the 13 identified genes involved in "energy production and conversion," and the Clp protease gene (RS_RS08645) is one of the 11 identified genes assigned to "posttranslational modification, protein turnover, and chaperones." Both genes were confirmed to be required for survival in plants. In conclusion, this study globally identified and validated R. solanacearum genes required for survival in tomato plants and provided essential information for a more complete view of the pathogenic mechanism of R. solanacearum. IMPORTANCE Tomato plant xylem is a nutritionally limiting and dynamically changing habitat. Studies on how R. solanacearum survives in this hostile environment are important for our full understanding of the pathogenic mechanism of this bacterium. Though many omics approaches have been employed to study in planta survival strategies, the direct genome-wide identification of R. solanacearum genes required for survival in plants is still lacking. This study performed a Tn-seq analysis in R. solanacearum and revealed that genes in the categories "cell wall/membrane/envelope biogenesis," "amino acid transport and metabolism," "energy production and conversion," "posttranslational modification, protein turnover, chaperones" and others play important roles in the survival of R. solanacearum in tomato plants.

The essential genome of Ralstonia solanacearum.

Ralstonia solanacearum is a scientifically/economically important plant pathogenic bacterium. The plant disease caused by R. solanacearum causes huge economic losses, and efficient control measures for the disease remain limited. To gain a better system-level understanding of R. solanacearum, we generated a near-saturated transposon insertion library of R. solanacearum GMI1000 with approximately 240,000 individual insertion mutants. Transposon sequencing (Tn-seq) allowed the mapping of 70.44%-80.96% of all potential insertion sites of the mariner C9 transposase in the genome of R. solanacearum and the identification of 465 genes essential for the growth of R. solanacearum in rich medium. Functional and comparative analyses of essential genes revealed that many basic physiological and biochemical processes such as transcription differ between R. solanacearum and other bacteria. A comparative analysis of essential genes also suggested that 34 genes might be essential only for Ralstonia group bacteria, whereas another 16 essential genes are unique to Ralstonia, providing high-priority candidate targets for developing R. solanacearum-specific drugs.