Xanthomonas Campestris Pathovar Research Articles

The Type III Effector XopLXcc in Xanthomonas campestris pv. campestris Targets the Proton Pump Interactor 1 and Suppresses Innate Immunity in Arabidopsis.

Xanthomonas campestris pathovar campestris (Xcc) is a significant phytopathogen causing black rot disease in crucifers. Xcc injects a variety of type III effectors (T3Es) into the host cell to assist infection or propagation. A number of T3Es inhibit plant immunity, but the biochemical basis for a vast majority of them remains unknown. Previous research has revealed that the evolutionarily conserved XopL-family effector XopLXcc inhibits plant immunity, although the underlying mechanisms remain incompletely elucidated. In this study, we identified proton pump interactor (PPI1) as a specific virulence target of XopLXcc in Arabidopsis. Notably, the C-terminus of PPI1 and the Leucine-rich repeat (LRR) domains of XopLXcc are pivotal for facilitating this interaction. Our findings indicate that PPI1 plays a role in the immune response of Arabidopsis to Xcc. These results propose a model in which XopLXcc binds to PPI1, disrupting the early defense responses activated in Arabidopsis during Xcc infection and providing valuable insights into potential strategies for regulating plasma membrane (PM) H+-ATPase activity during infection. These novel insights enhance our understanding of the pathogenic mechanisms of T3Es and contribute to the development of effective strategies for controlling bacterial diseases.

Functional characterization and transcriptional analysis of degQ of Xanthomonas campestris pathovar campestris.

High-temperature-requirement protein A (HtrA) family proteins play important roles in controlling protein quality and are recognized as virulence factors in numerous animal and human bacterial pathogens. The role of HtrA family proteins in plant pathogens remains largely unexplored. Here, we investigated the HtrA family protein, DegQ, in the crucifer black rot pathogen Xanthomonas campestris pathovar campestris (Xcc). DegQ is essential for bacterial attachment and full virulence of Xcc. Moreover, the degQ mutant strain showed increased sensitivity to heat treatment and sodium dodecyl sulfate. Expressing the intact degQ gene in trans in the degQ mutant could reverse the observed phenotypic changes. In addition, we demonstrated that the DegQ protein exhibited chaperone-like activity. Transcriptional analysis displayed that degQ expression was induced under heat treatment. Our results contribute to understanding the function and expression of DegQ of Xcc for the first time and provide a novel perspective about HtrA family proteins in plant pathogen.

SsrA and SmpB have multifaceted physiological roles in the black rot pathogen Xanthomonas campestris pathovar campestris.

SsrA and SmpB are known to play important roles in translational quality control and are essential for virulence in many human and animal pathogenic bacteria. The physiological roles and contribution of SsrA and SmpB to plant pathogen are unclear. Here, we present evidence to show that ssrA and smpB are involved in pathogenesis of Xanthomonas campestris pathovar campestris, the cause of black rot diseases in crucifers. The ssrA and smpB mutants exhibited defects in bacterial attachment, cell motility, and extracellular enzyme activity. The mutation of ssrA and smpB also resulted in a reduction in temperature tolerance. These altered phenotypes of the ssrA and smpB mutants could be complemented to wild-type levels by the intact ssrA and smpB genes. This is the first demonstration of the roles of SsrA and SmpB in phytopathogen.

Cruciferous Weed Isolates of Xanthomonas campestris Yield Insight into Pathovar Genomic Relationships and Genetic Determinants of Host and Tissue Specificity.

Pathovars of Xanthomonas campestris cause distinct diseases on different brassicaceous hosts. The genomic relationships among pathovars as well as the genetic determinants of host range and tissue specificity remain poorly understood despite decades of research. Here, leveraging advances in multiplexed long-read technology, we fully sequenced the genomes of a collection of X. campestris strains isolated from cruciferous crops and weeds in New York and California as well as strains from global collections, to investigate pathovar relationships and candidate genes for host- and tissue-specificity. Pathogenicity assays and genomic comparisons across this collection and publicly available X. campestris genomes revealed a correlation between pathovar and genomic relatedness and provide support for X. campestris pv. barbareae, the validity of which had been questioned. Linking strain host range with type III effector repertoires identified AvrAC (also 'XopAC') as a candidate host-range determinant, preventing infection of Matthiola incana, and this was confirmed experimentally. Furthermore, the presence of a copy of the cellobiosidase gene cbsA with coding sequence for a signal peptide was found to correlate with the ability to infect vascular tissues, in agreement with a previous study of diverse Xanthomonas species; however, heterologous expression in strains lacking the gene gave mixed results, indicating that factors in addition to cbsA influence tissue specificity of X. campestris pathovars. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Cruciferous Weeds Do Not Act as Major Reservoirs of Inoculum for Black Rot Outbreaks in New York State.

Cruciferous weeds have been shown to harbor diverse Xanthomonas campestris pathovars, including the agronomically damaging black rot of cabbage pathogen, X. campestris pv. campestris. However, the importance of weeds as inoculum sources for X. campestris pv. campestris outbreaks in New York remains unknown. To determine if cruciferous weeds act as primary reservoirs for X. campestris pv. campestris, fields that were rotating between cabbage or had severe black rot outbreaks were chosen for evaluation. Over a consecutive 3-year period, 148 cruciferous and noncruciferous weed samples were collected at 34 unique sites located across five New York counties. Of the 148 weed samples analyzed, 48 X. campestris isolates were identified, with a subset characterized using multilocus sequence analysis. All X. campestris isolates originated from weeds belonging to the Brassicaceae family, with predominant weed hosts being shepherd's purse (Capsella bursa-pastoris), wild mustard (Sinapis arvensis), yellow rocket (Barbarea vulgaris), and pennycress (Thlaspi arvense). Identifying pathogenic X. campestris weed isolates was rare, with only eight isolates causing brown necrotic leaf spots or typical V-shaped lesions on cabbage. There was no evidence of cabbage-infecting weed isolates persisting in an infected field by overwintering in weed hosts; however, similar cabbage and weed X. campestris haplotypes were identified in the same field during an active black rot outbreak. X. campestris weed isolates are genetically diverse both within and between fields, but our findings indicate that X. campestris weed isolates do not appear to act as primary sources of inoculum for B. oleracea fields in New York.

Detailed analysis of the fatty acid composition of six plant-pathogenic bacteria

Bacteria show distinct and characteristic fatty acid (FA) patterns which can be modified by environmental conditions. In this study, we cultivated six plant-pathogenic bacteria of agricultural concern and performed a detailed analysis of the fatty acid composition. The study covered four strains of the gram-negative Xanthomonas campestris pathovar (pv) campestris (Xcc), Xanthomonas perforans (Xp), Acidovorax citrulli (Ac) and Pseudomonas syringae pv. tomato (Pst), and two strains of the gram-positive Clavibacter michiganensis subsp. michiganensis (Cmm) and Streptomyces scabies (Ssc). After cultivation, freeze-dried bacteria samples were transesterified and analysed by gas chromatography with mass spectrometry in full scan and selected ion monitoring (SIM) modes. Altogether, 44 different FAs were detected in the six strains with individual contributions of 0.01–43.8% to the total FAs. The variety in the six strains ranged between 12 and 31 individual FAs. The FA composition of Xcc, Xp, Cmm and Ssc were dominated by iso- and anteiso-fatty acids (especially i15:0, a15:0, i16:0), which is typical for most bacteria. In contrast to this, Ac and Pst showed only saturated and monounsaturated FAs. Four of the six bacteria showed similar FA patterns as reported before in the literature. Differences were observed in the case of Cmm where many more FAs were detected in the present study. In addition, to the best of our knowledge, the FA pattern of Xp was presented for the first time.

Xanthomonas campestris Pathovars.

This infographic describes those regulated traits and pathogenicity determinants of Xanthomonas campestris pathovars that are key for interactions with plants.

Genetic analysis of resistance to bacterial leaf spot in the heirloom lettuce cultivar Reine des Glaces

Bacterial leaf spot (BLS) is a disease that affects lettuce (Lactuca sativa L.) worldwide. The disease is caused by the bacterium Xanthomonas campestris pathovar vitians (Xcv), which exclusively infects lettuce and is particularly devastating in warm humid climates. Reine des Glaces (RG), an old Batavia-type cultivar, exhibited an uninvestigated partial resistance to Xcv. Quantitative trait loci (QTLs) were analyzed using two recombinant inbred line (RIL) populations derived from RG × Eruption and RG × Delsay using three isolates collected in California and Canada, each representing a different race, and an isolate collected in France. A major QTL was identified in linkage group 2 in both populations; additional, minor QTLs were also detected in other linkage groups. The major QTL collocates with the Xanthomonas resistance 1 (Xar1) and Xanthomonas campestris vitians resistance (Xcvr) genes that had previously been identified using RIL populations derived from Salinas 88 × La Brillante and PI 358001-1 × Tall Guzmaine. RG provides another resistance resource for combating BLS using data provided by this study for marker-assisted selection.

The crystal structure of the phytopathogenic bacterial sensor PcrK reveals different cytokinin recognition mechanism from the plant sensor AHK4

Plant cytokinins (CKs) are essential for many central cellular processes and play important roles in the interaction between bacteria and plants. Perception of CK is executed by the CHASE domain in the histidine kinase sensors of a class of two-component regulatory systems. Despite advances in understanding the structural basis for CK perception by the sensor AHK4 in Arabidopsis, the molecular mechanism of CK binding by other sensors is unclear. Here, we report the crystal structure of the CHASE domain in the histidine kinase PcrK of the bacterial plant pathogen Xanthomonas campestris pathovar campestris, which senses plant CK, determined at 2.55 Å resolution. The structure reveals that the PcrK has an AHK4-like overall topology and assembles into a homodimer. Strikingly, detailed structural analysis unveils two unique features of the PcrK ligand binding pocket: the size of the pocket is restricted for CK binding, and the PcrK applies a positively charged arginine but not a negatively charged aspartate to recognize the ligand. We propose a model to explain how the PcrK accommodates CK-sized compounds through conformational changes, providing a potential mechanistic framework for understanding ligand recognition by the PcrK.

A type III effector XopLXcc8004 is vital for Xanthomonas campestris pathovar campestris to regulate plant immunity

Xanthomonas campestris pv. campestris (Xcc) secretes a suite of effectors into host plants via the type III secretion system (T3SS), modulating plant immunity defenses. Strain Xcc8004 causes black rot in brassica plants, including Arabidopsis thaliana, making it a classical model for the study of Xanthomonas pathogenesis. XopLXcc8004 was defined as a T3SS effector (T3SE) since its homologues XopLXcv85-10 from Xanthomonas campestris pv. vesicatoria (Xcv85-10) contribute to virulence in host plants. Except for its virulence on Chinese radish plants, little was previously known about the regulation and function of XopLXcc8004. Here, we tested the role of XopLXcc8004 in the pathogenicity of Xcc8004 on different host plants including Arabidopsis. We found that it was required for full virulence of Xcc8004 in Chinese cabbage. XopLXcc8004 promoted bacterial infection in Arabidopsis and suppressed bacterial flagellin (flg22)-induced FRK1 transcription, reactive oxygen species (ROS) burst, callose deposition, and pathogenesis-related marker gene expression, but it did not affect mitogen-activated protein kinases (MAPKs) cascade. Early and prolonged expression of XopLXcc8004 affected Arabidopsis growth and development. We demonstrated that XopLXcc8004 is a virulence factor and interferes with innate immunity of Arabidopsis by suppressing pathogen-associated molecular pattern-triggered immunity (PTI) signaling, independent of MAPKs.

Retraction: Detection and Functional Characterization of a 215 Amino Acid N-Terminal Extension in the Xanthomonas Type III Effector XopD.

During evolution, pathogens have developed a variety of strategies to suppress plant-triggered immunity and promote successful infection. In Gram-negative phytopathogenic bacteria, the so-called type III protein secretion system works as a molecular syringe to inject type III effectors (T3Es) into plant cells. The XopD T3E from the strain 85-10 of Xanthomonas campestris pathovar vesicatoria (Xcv) delays the onset of symptom development and alters basal defence responses to promote pathogen growth in infected tomato leaves. XopD was previously described as a modular protein that contains (i) an N-terminal DNA-binding domain (DBD), (ii) two tandemly repeated EAR (ERF-associated amphiphillic repression) motifs involved in transcriptional repression, and (iii) a C-terminal cysteine protease domain, involved in release of SUMO (small ubiquitin-like modifier) from SUMO-modified proteins. Here, we show that the XopD protein that is produced and secreted by Xcv presents an additional N-terminal extension of 215 amino acids. Closer analysis of this newly identified N-terminal domain shows a low complexity region rich in lysine, alanine and glutamic acid residues (KAE-rich) with high propensity to form coiled-coil structures that confers to XopD the ability to form dimers when expressed in E. coli. The full length XopD protein identified in this study (XopD1-760) displays stronger repression of the XopD plant target promoter PR1, as compared to the XopD version annotated in the public databases (XopD216-760). Furthermore, the N-terminal extension of XopD, which is absent in XopD216-760, is essential for XopD type III-dependent secretion and, therefore, for complementation of an Xcv mutant strain deleted from XopD in its ability to delay symptom development in tomato susceptible cultivars. The identification of the complete sequence of XopD opens new perspectives for future studies on the XopD protein and its virulence-associated functions in planta.

Inference of the phylogenetic diversity and population structure of Xanthomonas campestris affecting Brassicaceae using a multilocus sequence typing‐based approach

Xanthomonas campestris pathovars are widely distributed throughout the globe and have a broad host range, causing severe economic losses in the food and ornamental crucifers markets. Using an approach based on multilocus sequence typing, phylogenetic diversity and population structure of a set of 75 Portuguese and other Xanthomonas campestris isolates from several cruciferous hosts were assessed. Although this population displayed a major clonal structure, neighbour‐net phylogenetic analysis highlighted the presence of recombinational events that may have driven the ecological specialization of X. campestris with different host ranges within the Brassicaceae family. A high level of genetic diversity within and among X. campestris pathovars was also revealed, through the establishment of 46 sequence types (STs). This approach provided a snapshot of the global X. campestris population structure in cruciferous host plants, correlating the existing pathovars with three distinct genetic lineages. Phylogenetic relationships between the founder genotype and remaining isolates that constitute the X. campestris pv. campestris population were further clarified using goeBURST algorithm. Identification of an intermediate link between X. campestris pv. campestris and X. campestris pv. raphani provided new insights into the mechanisms driving the differentiation of both pathovars. Wide geographic distribution of allelic variants suggests that evolution of X. campestris as a seedborne pathogen was not shaped by natural barriers. However, as Portuguese isolates encompass 26 unique STs and this country is an important centre of domestication of Brassica oleracea crops, a strong case is made for its role as a diversification reservoir, most probably through host–pathogen coevolution.

Competence of Xanthomonas campestris from Cruciferous Weeds and Wallflower (Erysimum cheiri) to Induce Black Rot in Cabbage

In order to verify the role of cruciferous weeds and ornamentals to serve as a source of primary inoculum of Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot of Brassicas, Xanthomonas isolates from shepherd’s purse (Capsella bursa-pastoris), fanweed (Thlaspi arvense) and wallflower (Erysimum cheiri) were characterized by molecular data and by their pathogenicity on kohlrabi and shepherd’s purse. These characteristics were compared to those of xanthomonads isolated from infested Brassica crops and contaminated transplants. Only one of 30 Xanthomonas isolates from shepherd’s purse in boundary ridges and field paths adjacent to Brassica fields, and from plants outside the Brassica growing area, was able to induce black rot (BR) on kohlrabi; nearly all of them (except one) were able to cause black rot like symptoms with black vascular veins (BRL) on shepherd’s purse. Six of ten tested isolates from different asymptomatic weeds growing in BR infested cauliflower fields were able to induce BR on kohlrabi, but all isolates caused BRL on shepherd’s purse. All Xanthomonas isolates from symptomatic wallflower induced BR on kohlrabi and BRL on shepherd’s purse. Inoculations with isolates from BR infested cauliflower, representing the pathovar campestris (Xcc), always led to BR on kohlrabi and BRL on shepherd’s purse. The isolates from rucola and radish field crops and from Brassica transplants showed typical symptoms of the pathovars campestris (Xcc) and raphani (Xcr), respectively. In a PCR with the newly designed primer set SP-1, only the isolates which were able to induce BR on kohlrabi could be detected. The sequence analysis of the gyrB-gene showed that all Xanthomonas isolates which induced BR on kohlrabi clustered in one major clade, while the remaining isolates clustered into several different clades. Based on these results, the authors conclude that Xanthomonas isolates from shepherd’s purse may not constitute a serious risk to serve as primary inoculum for BR epidemics in Brassicas. By contrast, Xanthomonas isolates from wallflower have this potential. Most of the isolates from cruciferous weeds and the wallflower isolates do not fit into the actual classification of Xanthomonas campestris pathovars.

Corrigendum

Functional EcologyVolume 31, Issue 8 p. 1670-1670 CorrigendumFree Access Corrigendum This article corrects the following: Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps Camille Ponzio, Berhane T. Weldegergis, Marcel Dicke, Rieta Gols, Sergio Rasmann, Volume 30Issue 11Functional Ecology pages: 1779-1789 First Published online: June 28, 2016 First published: 10 July 2017 https://doi.org/10.1111/1365-2435.12931Citations: 1AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Ponzio, C., Weldegergis, B.T., Dicke, M. & Gols, R. (2016) Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps. Functional Ecology, 30, 1779–1789. https://doi.org/10.1111/1365-2435.12689. After publication of this article the authors carried out some further symptom development and PCR analyses of the bacterial strains used. Based on these analyses the authors have found that the virulent pathogen used in the article was in fact Xanthomonas campestris pathovar raphani, (formerly known as Xanthomonas campestris pathovar armoraciae), not Xanthomonas campestris pathovar campestris as listed in the article. The journal editors and authors are satisfied that this error does not affect the results or conclusions of the article. The authors apologise for any confusion or inconvenience caused by this error. Reference Ponzio, C., Weldegergis, B.T., Dicke, M., & Gols, R. (2016) Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps. Functional Ecology, 30, 1779– 1789. https://doi.org/10.1111/1365-2435.12689 Citing Literature Volume31, Issue8August 2017Pages 1670-1670 ReferencesRelatedInformation

Probing the Role of Cyclic di-GMP Signaling Systems in Disease Using Chinese Radish.

The determination of the genome sequences of pathogenic bacteria has facilitated functional analyses that aim to understand the molecular basis of virulence. In particular, genome sequence information of the pathogen Xanthomonas campestris pathovar campestris has allowed researchers to identify and functionally analyze the role of intracellular signaling involving cyclic di-GMP in black rot disease of crucifers. Here, we describe leaf clipping and spraying methods for testing the virulence of wild type and derived mutants of X. campestris in Chinese radish. These methods address different facets of the disease cycle, which requires the ability to survive epiphytically before entry into the plant and growth and systemic spread within the xylem.

Rapid, specific, simple, in-field detection of Xanthomonas campestris pathovar musacearum by loop-mediated isothermal amplification.

To develop and evaluate a loop-mediated isothermal amplification (LAMP) assay for Xanthomonas campestris pathovar musacearum (Xcm), the causal agent of banana Xanthomonas wilt, a major disease of banana in Africa. LAMP primers were designed to the general secretion pathway protein D gene and tested against 17 isolates of Xcm encompassing the known genetic and geographic diversity of the bacterium and all isolates were detected. Seventeen other Xanthomonas isolates, including closely related Xanthomonas vasicola, other bacterial pathogens/endophytes of Musa and two healthy Musa varieties gave negative results with the LAMP assay. The assay showed good sensitivity, detecting as little as 51fg of Xcm DNA, a greater level of sensitivity than that of an Xcm PCR assay. Amplification with the LAMP assay was very rapid, typically within 9min from bacterial cultures. Symptomatic field samples of Musa from Uganda were tested and all produced amplification in less than 13min. The LAMP assay provides rapid, sensitive detection of the pathogen that is ideally suited for deployment in laboratories with basic facilities and in-field situations. This is the first LAMP assay for Xcm which provides a significant improvement compared to existing diagnostics.

English

Previous biochemical and molecular sequence analyses of Xanthomonas campestris pathovar musacearum, the etiological agent of banana Xanthomonas wilt, suggest that it belongs within the species Xanthomonas vasicola (X. vasicola pv. vasculorum and X. vasicola pathovar holcicola. However, the X. vasicola pathovar names were considered invalid according to pathovar naming standards and placed as one X. vasicola species; this was also not helped by the lack of sufficient comparative pathogenicity studies. Hence the proposal to rename X. campestris pathovar musacearum was no longer further supported. This study therefore carried out large scale comparative pathogenicity trial studies on the X. vasicola strains and X. campestris pathovar musacearum on 112 plants for banana and maize, and 84 plants for sugarcane, to establish or support the proper X. vasicola pathovar designations. The study also included nine common plant pathogenic Xanthomonas pathovars and one non-Xanthomonas strain. The six strains of X. campestris pathovar musacearum used in the study caused disease in sugarcane and banana but not on maize. 2 and 4 strains of X. vasicola pathovar vasculorum and X. vasicola pathovar holcicola, respectively were not only pathogenic on maize and sugarcane but each also caused distinct symptoms on maize. X. vasicola pathovar vasculorum caused deformation of the plant while X. vasicola pathovar holcicola caused stunted growth. Key words: Pathogenicity, X. axonopodis pv. vasculorum, X.campestris pv. musacearum, X vasicola pv. holcicola, X. vasicola pv. vasculorum, Xanthomonas wilt of bananas.

Aggressive Emerging Pathovars of Xanthomonas arboricola Represent Widespread Epidemic Clones Distinct from Poorly Pathogenic Strains, as Revealed by Multilocus Sequence Typing.

Deep and comprehensive knowledge of the genetic structure of pathogenic species is the cornerstone on which the design of precise molecular diagnostic tools is built. Xanthomonas arboricola is divided into pathovars, some of which are classified as quarantine organisms in many countries and are responsible for diseases on nut and stone fruit trees that have emerged worldwide. Recent taxonomic studies of the genus Xanthomonas showed that strains isolated from other hosts should be classified in X. arboricola, extending the host range of the species. To investigate the genetic structure of X. arboricola and the genetic relationships between highly pathogenic strains and strains apparently not relevant to plant health, we conducted multilocus sequence analyses on a collection of strains representative of the known diversity of the species. Most of the pathovars were clustered in separate monophyletic groups. The pathovars pruni, corylina, and juglandis, responsible for pandemics in specific hosts, were highly phylogenetically related and clustered in three distinct clonal complexes. In contrast, strains with no or uncertain pathogenicity were represented by numerous unrelated singletons scattered in the phylogenic tree. Depending on the pathovar, intra- and interspecies recombination played contrasting roles in generating nucleotide polymorphism. This work provides a population genetics framework for molecular epidemiological surveys of emerging plant pathogens within X. arboricola. Based on our results, we propose to reclassify three former pathovars of Xanthomonas campestris as X. arboricola pv. arracaciae comb. nov., X. arboricola pv. guizotiae comb. nov., and X. arboricola pv. zantedeschiae comb. nov. An emended description of X. arboricola Vauterin et al. 1995 is provided.

Characterization of the pyrophosphate-dependent 6-phosphofructokinase from Xanthomonas campestris pv. campestris

Xanthomonads are plant pathogenic proteobacteria that produce the polysaccharide xanthan. They are assumed to catabolize glucose mainly via the Entner–Doudoroff pathway. Whereas previous studies have demonstrated no phosphofructokinase (PFK) activity in xanthomonads, detailed genome analysis revealed in Xanthomonas campestris pathovar campestris (Xcc) genes for all Embden–Meyerhof–Parnas pathway (glycolysis) enzymes, including a conserved pfkA gene similar to 6-phosphofructokinase genes. To address this discrepancy between genetic and physiological properties, the pfkA gene of Xcc strain B100 was cloned into the expression vector pET28a+. The 45-kDa pfkA gene product exhibited no conventional PFK activity. Bioinformatic analysis of the Xcc PfkA amino acid sequence suggested utilization of pyrophosphate as an alternative cosubstrate. Pyrophosphate-dependent PFK activity was shown in an in vitro enzyme assay for purified Xcc PfkA, as well as in the Xcc B100 crude protein extract. Kinetic constants were determined for the forward and reverse reactions. Primary structure conservation indicates the global presence of similar enzymes among Xanthomonadaceae.

Transcriptome profiling of Xanthomonas campestris pv. campestris grown in minimal medium MMX and rich medium NYG

Xanthomonas campestris pathovar campestris (Xcc) is the causal agent of black rot disease in cruciferous plants worldwide. Although the complete genomes of several Xcc strains have been determined, the gene expression and regulation mechanisms in this pathogen are far from clear. In this work, transcriptome profiling of Xcc 8004 grown in MMX medium (minimal medium for Xanthomonas campestris) and NYG medium (peptone yeast glycerol medium) were investigated by RNA-Seq. Using the Illumina HiSeq 2000 platform, a total of 26,514,630 reads (90 nt in average) were generated, of which 15,708,478 reads mapped uniquely to coding regions of Xcc 8004 genome. Of the 4273 annotated protein-coding genes of Xcc 8004, 629 were found differentially expressed in Xcc grown in MMX and NYG. Of the differentially expressed genes, 495 were up-regulated and 134 were down-regulated in MMX. The MMX-induced genes are mainly involved in amino acid metabolism, transport systems, atypical condition adaptation and pathogenicity, especially the type III secretion system, while the MMX-repressed genes are mainly involved in chemotaxis and degradation of small molecules. The global transcriptome analyzes of Xcc 8004 grown in MMX and NYG might facilitate the gene functional characterization of this phytopathogenic bacterium.