Phytoplasmas are plant pathogenic bacteria that have no cell wall and are responsible for major crop losses throughout the world. Phytoplasma-infected plants show a variety of symptoms and the mechanisms they use to physiologically alter the host plants are of considerable interest, but poorly understood. In this study we undertook a detailed analysis of Paulownia infected by Paulownia witches’-broom (PaWB) Phytoplasma using high-throughput mRNA sequencing (RNA-Seq) and digital gene expression (DGE). RNA-Seq analysis identified 74,831 unigenes, which were subsequently used as reference sequences for DGE analysis of diseased and healthy Paulownia in field grown and tissue cultured plants. Our study revealed that dramatic changes occurred in the gene expression profile of Paulownia after PaWB Phytoplasma infection. Genes encoding key enzymes in cytokinin biosynthesis, such as isopentenyl diphosphate isomerase and isopentenyltransferase, were significantly induced in the infected Paulownia. Genes involved in cell wall biosynthesis and degradation were largely up-regulated and genes related to photosynthesis were down-regulated after PaWB Phytoplasma infection. Our systematic analysis provides comprehensive transcriptomic data about plants infected by Phytoplasma. This information will help further our understanding of the detailed interaction mechanisms between plants and Phytoplasma.

Two Gram-stain negative aerobic bacterial strains were isolated from the bark tissue of Populus × euramericana. The novel isolates were investigated using a polyphasic approach including 16S rRNA gene sequencing, genome sequencing, average nucleotide identity (ANI) and both phenotypic and chemotaxonomic assays. The genome core gene sequence and 16S rRNA gene phylogenies suggest that the novel isolates are different from the genera Snodgrassella and Stenoxybacter. Additionally, the ANI, G+C content, main fatty acids and phospholipid profile data supported the distinctiveness of the novel strain from genus Snodgrassella. Therefore, based on the data presented, the strains constitute a novel species of a novel genus within the family Neisseriaceae, for which the name Populibacter corticis gen. nov., sp. nov. is proposed. The type strain is 15-3-5T (= CFCC 13594T = KCTC 42251T).

Five Gran-stain-negative, facultatively anaerobic, motile, bacterial strains were isolated from symptomatic bark tissue of Populus¾euramericana canker. Strains grew at 4-41 6C, pH 4-10 and 0-6 % (w/v) salinity. They were positive with respect to catalase activity and negative for oxidase activity, nitrate reduction and the Voges-Proskauer reaction. Analysis of 16S rRNA gene sequences indicated that these five poplar isolates belong to the genus Brenneria, having highest sequence similarity of 95.98 % with Brenneria goodwinii LMG 26270 T . These five isolates formed a single cluster based on multilocus sequence analysis, indicating that they all belong to a single taxon within the genus Brenneria, which was confirmed by DNA-DNA hybridization. The DNA G+C content was 54.9-55.7 mol%, and the main fatty acids were C 16 : 0 , C 18 : 1 v7c, C 17 : 0 cyclo and C 16 : 1 v7c/iso-C 15 : 0 2-OH. Based on these results, we describe a novel species of the genus Brenneria with the proposed name Brenneria populi sp. nov. The type strain is D9-5 T (5CFCC 11963 T 5KCTC 42088 T ).The genus Brenneria was first established by Hauben et al. (1998a). At the time of writing, the genus Brenneria comprises five species with validly published names. Almost all species of the genus are plant pathogens. Brenneria salicis (the type species of the genus) causes willow (Salix spp.) watermark disease, and occurs mainly in the xylem vessels of the host plants (Hauben et al., 1998b). There are also three species which can cause plant bark canker disease. Brenneria nigrifluens and Brenneria rubrifaciens are the causal agents of bark canker and deep bark canker of walnut, respectively (Loreti et al., 2008;McClean et al., 2008). Brenneria alni is the causal agent of bark canker of alder (Surico et al., 1996). Moreover, another two species, namely Brenneria goodwinii and 'Brenneria roseae' (including two subspecies), which were isolated from symptomatic oak tissues, are both associated with acute oak decline (Denman et al., 2012;Brady et al., 2014). Here, we describe the phenotypic and genotypic properties of five novel strains representing the genus Brenneria isolated from symptomatic bark of Populus6euramericana canker in Henan Province of China. The Populus6euramericana canker with abundant white, sour exudates on poplar trees more than five years old were observed for the first time in China's Henan and Shandong provinces in 2006. Diseased plants had stem or branch bark that cracked and exuded frothy fluid. When the disease progressed, many cankers (50-15063-8 cm, width by length) appeared rapidly (Li et al., 2014). Lonsdalea quercina subsp. populi proved to be the causal agent of the bark canker (Li et al., 2014).During our research on pathogen isolation from Populus6euramericana canker, besides the pathogen L. quercina subsp. populi, five other strains (D9-5 T 5CFCC