Project description:In the xylem vessels of susceptible hosts, such as citrus trees or grapevines, Xylella fastidiosa forms biofilm like-colonies that can block water transport, which appears to correlate to disease symptoms. Besides helping host colonization, bacterial biofilms play an important role in resistance against antimicrobial agents, for instance antimicrobial peptides (AMP). Here we show that gomesin, a potent AMP from a Brazilian tarantula spider, modulates X. fastidiosa gene expression profile upon 60 min treatment with a sublethal concentration. Data from DNA microarray hybridizations revealed that among the up-regulated coding sequences (CDS), some are related to biofilm production. In addition, we show that the biofilm formed by gomesin-treated bacteria is thicker than that formed by non-treated cells or cells exposed to streptomycin. We have also observed that treatment of X. fastidiosa with sublethal concentration of gomesin before inoculation in tobacco plants correlates with reduction in CVC symptoms, an effect possibly due to trapping of bacterial cells to fewer xylem vessels given the enhancement in biofilm production. Together, our results suggest that X. fastidiosa can selectively sense a sublethal concentration of gomesin modulating its gene expression to produce a stronger biofilm that may protect itself against the toxic effects of this AMP.
Project description:In the xylem vessels of susceptible hosts, such as citrus trees or grapevines, Xylella fastidiosa forms biofilm like-colonies that can block water transport, which appears to correlate to disease symptoms. Besides helping host colonization, bacterial biofilms play an important role in resistance against antimicrobial agents, for instance antimicrobial peptides (AMP). Here we show that gomesin, a potent AMP from a Brazilian tarantula spider, modulates X. fastidiosa gene expression profile upon 60 min treatment with a sublethal concentration. Data from DNA microarray hybridizations revealed that among the up-regulated coding sequences (CDS), some are related to biofilm production. In addition, we show that the biofilm formed by gomesin-treated bacteria is thicker than that formed by non-treated cells or cells exposed to streptomycin. We have also observed that treatment of X. fastidiosa with sublethal concentration of gomesin before inoculation in tobacco plants correlates with reduction in CVC symptoms, an effect possibly due to trapping of bacterial cells to fewer xylem vessels given the enhancement in biofilm production. Together, our results suggest that X. fastidiosa can selectively sense a sublethal concentration of gomesin modulating its gene expression to produce a stronger biofilm that may protect itself against the toxic effects of this AMP. Two-condition experiment, control (PW media) vs. gomesin-treated cells. Biological replicates: 5 control, 5 gomesin-treated, independently grown and harvested. Two replicates (left and right side of slide) per array. Total of 10 slides were hibridized, including dye-swap of and two self-self experiments.
Project description:This is the study of the Heat Shock response of phytopathogenic bacteria Xylella fastidiosa. This series keeps the 25 minutes 40oC stimulus response (Aug 2005). Keywords: stress response; heat shock response
Project description:Pierce's disease (PD) in grapevine (Vitis vinifera) is caused by the bacterial pathogen Xylella fastidiosa. X. fastidiosa is limited to the xylem tissue and following infection induces extensive plant‐derived xylem blockages, primarily in the form of tyloses. Tylose‐mediated vessel occlusions are a hallmark of PD, particularly in susceptible V. vinifera. We temporally monitored tylose development over the course of the disease to link symptom severity to the level of tylose occlusion and the presence/absence of the bacterial pathogen at fine‐scale resolution. The majority of vessels containing tyloses were devoid of bacterial cells, indicating that direct, localized perception of X. fastidiosa was not a primary cause of tylose formation. In addition, we used X‐ray computed microtomography and machine‐learning to determine that X. fastidiosa induces significant starch depletion in xylem ray parenchyma cells. This suggests that a signalling mechanism emanating from the vessels colonized by bacteria enables a systemic response to X. fastidiosa infection. To understand the transcriptional changes underlying these phenotypes, we integrated global transcriptomics into the phenotypes we tracked over the disease spectrum. Differential gene expression analysis revealed that considerable transcriptomic reprogramming occurred during early PD before symptom appearance. Specifically, we determined that many genes associated with tylose formation (ethylene signalling and cell wall biogenesis) and drought stress were up‐regulated during both Phase I and Phase II of PD. On the contrary, several genes related to photosynthesis and carbon fixation were down‐regulated during both phases. These responses correlate with significant starch depletion observed in ray cells and tylose synthesis in vessels.
Project description:PAMP-triggered immunity (PTI) is the first line of plant defense against invading organisms. Initiated through the perception of conserved pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharide or flagellin, PTI can provide early protection against a broad range of pathogens. Active suppression of PTI by microbial effector proteins, particularly those secreted by the Type III secretion system (T3SS), is a well-known strategy employed by bacterial plant pathogens that enables them to subvert PTI and successfully colonize their hosts. In this study, we demonstrate that the xylem-limited bacterium, Xylella fastidiosa, which lacks a T3SS, utilizes an alternative strategy to delay elicitation of innate immune responses. By decorating its LPS PAMP molecule with a high molecular weight O antigen, this bacterium physically masks itself from early recognition by the grapevine innate immune system. We have elucidated the chemical structure of the O antigen and found that it is primarily an α1,2-linked rhamnan polymer. X. fastidiosa cells lacking O antigen elicited hallmarks of PTI such as ROS production, specifically in the plant xylem tissue compartment, which is comprised primarily of non-living cells. By coupling histological and genome-wide transcriptional profiling, we demonstrate that X. fastidiosa lacking its O antigen shield activates defense-related genes in grapevine. This includes a stronger and more prolonged oxidative burst at concentrations high enough to inhibit pathogen proliferation. To begin exploring translational applications of our findings, we also demonstrate that purified X. fastidiosa LPS elicitor can prime grapevine defenses, thereby conferring host tolerance to subsequent challenge with X. fastidiosa.
Project description:Background: Xylella fastidiosa, a Gram-negative fastidious bacterium, grows exclusively in the xylem of several plants, causing diseases such as citrus variegated chlorosis. As the xylem sap contains low concentrations of amino acids and other compounds, X. fastidiosa needs to cope with nitrogen limitation in its natural habitat. Results: In this work, we performed a whole-genome microarray analysis of the X. fastidiosa nitrogen starvation response. A time-course experiment (2, 8 and 12 hours) revealed many differentially expressed genes under nitrogen starvation, such as genes related to transport, nitrogen assimilation, amino acid biosynthesis, transcriptional regulation, and many genes encoding hypothetical proteins. In addition, a decrease in the expression levels of many genes involved in carbon metabolism and energy generation pathways was also observed. Comparison of gene expression profiles between the wild type strain and the rpoN null mutant allowed the identification of genes induced by nitrogen starvation in a σ54-dependent manner. A more complete picture of the σ54 regulon was achieved by combining the transcriptome data with an in silico search for potential σ54-dependent promoters, using a position weight matrix approach. One of these σ54-predicted binding sites, located upstream of the glnA gene (encoding a glutamine synthetase), was validated by primer extension assays, confirming that this gene has a σ54-dependent promoter and contains a predicted NtrC binding site. Conclusions: Together, these results show that nitrogen starvation causes intense changes in the X. fastidiosa transcriptome and some of these differentially expressed genes belong to the σ54 regulon.
Project description:Citrus variegated chlorosis (CVC), caused by Xylella fastidiosa, is an important citrus disease that produces chlorotic injuries on leaves and reduced fruit size. This bacterium colonizes plant xylem, thereby interrupting sap flow. Other disease symptoms depend on environmental factors, since asymptomatic and symptomatic CVC plants may be genetically similar. The endophytic microbiome comprises many microbial species that may interact with pathogens, reducing disease symptoms and improving plant growth. However, the genetic and physiological mechanisms that underlie this interaction are largely unknown. In this study, the citrus endophytic bacterium Methylobacterium mesophilicum SR1.6/6 was isolated from healthy plants. This bacterium was able to colonize citrus xylem and could be transferred from plant to plant by Bucephalogonia xanthopis (Insecta), suggesting that this endophytic bacterium may interact with X. fastidiosa in planta, as a result of co-transmission by the same insect vector. To better understand how X. fastidiosa genetic responds to the presence of M. mesophilicum in the same environment, we used microarrays to evaluate the transcriptional profile of X. fastidiosa, after in vitro co-cultivation with M. mesophilicum SR1.6/6. The results showed that during co-cultivation with M. mesophilicum, X. fastidiosa downregulated genes related to growth, while genes related to energy production (cellular respiration) and transport were upregulated. Moreover, X. fastidiosa modulates genes associated with molecular recognition, nutrient competition and the stress response, suggesting the existence of a specific adaptive response to the presence of M. mesophilicum in the culture medium
Project description:Investigation of whole genome gene expression level changes in Xylella fastidiosa grown in minimal media XFM and XFM supplied with pectin or glucan (Host polysaccharides) , compared to cell grown in the complex media PWG. The cells grown in the minimal medium XFM supplied with host polysaccharides specially pectin are transmissible by the insect vector when delivered to the vector through artificial diet system. This does not happen with cells grown in the complex media. 4 (4 plex chips) study using total RNA recovered from 4 independents replicates for Xylella fastidiosa grown on PWG, XFM, XFM-glucan and XFM-pectin.
Project description:Genome sequence analysis of the bacterium Xylella fastidiosa revealed the presence of two genes, named rpoE and rseA, predicted to encode an ECF sigma factor and an anti-sigma factor, respectively. In this work, an rpoE null mutant was constructed in the citrus strain J1a12 and shown to be sensitive to exposure to heat shock and ethanol. To identify the X. fastidiosa σE regulon, global gene expression profiles were obtained by DNA microarray analysis of bacterial cells under heat shock identifying 23 sigmaE-dependent genes. Keywords: stress response, heat shock, rpoE mutant strain