Project description:Pierce's disease, caused by the bacterium Xylella fastidiosa, is one of the most devastating diseases of cultivated grapes. To test the long-standing hypothesis that Pierce's disease results from pathogen-induced drought stress, we used the Affymetrix Vitis GeneChip to compare the transcriptional response of Vitis vinifera to Xylella infection, water deficit, or a combination of the two stresses. The results reveal a massive redirection of gene transcription involving 822 genes with a minimum 2-fold change (p<0.05), including the upregulation of transcripts for phenylpropanoid and flavonoid biosynthesis, pathogenesis related (PR) proteins, absisic acid (ABA)/jasmonic acid (JA)-responsive transcripts, and down-regulation of transcripts related to photosynthesis, growth and nutrition. Although the transcriptional response of plants to Xylella infection was largely distinct from the response of healthy plants to water stress, we find that 138 of the pathogen-induced genes exhibited a significantly stronger transcriptional response when plants were simultaneously exposed to infection and drought stress, suggesting a strong interaction between disease and water deficit. This interaction between drought stress and disease was mirrored in planta at the physiological level for aspects of water relations and photosynthesis, and in terms of the severity of disease symptoms and the extent of pathogen colonization, providing a molecular correlation of the classical concept of the disease triangle where environment impacts disease severity. Mature leaves were sampled from 2-year old V. vinifera cv. Cabernet sauvignon clone 8 vines 4 and 8 weeks post-mock or inoculation with Xylella fastidiosa (Pierce's disease). Vines were grown in growth chambers under non-water limiting and water limiting conditions (moderate and severe water stress)
Project description:Pierce’s disease, caused by the bacterium Xylella fastidiosa, is one of the most devastating diseases of cultivated grapes. To test the long-standing hypothesis that Pierce’s disease results from pathogen-induced drought stress, we used the Affymetrix Vitis GeneChip to compare the transcriptional response of Vitis vinifera to Xylella infection, water deficit, or a combination of the two stresses. The results reveal a massive redirection of gene transcription involving 822 genes with a minimum 2-fold change (p<0.05), including the upregulation of transcripts for phenylpropanoid and flavonoid biosynthesis, pathogenesis related (PR) proteins, absisic acid (ABA)/jasmonic acid (JA)-responsive transcripts, and down-regulation of transcripts related to photosynthesis, growth and nutrition. Although the transcriptional response of plants to Xylella infection was largely distinct from the response of healthy plants to water stress, we find that 138 of the pathogen-induced genes exhibited a significantly stronger transcriptional response when plants were simultaneously exposed to infection and drought stress, suggesting a strong interaction between disease and water deficit. This interaction between drought stress and disease was mirrored in planta at the physiological level for aspects of water relations and photosynthesis, and in terms of the severity of disease symptoms and the extent of pathogen colonization, providing a molecular correlation of the classical concept of the disease triangle where environment impacts disease severity.
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:Xylella fastidiosa is a plant pathogenic bacterium that has been introduced in the European Union (EU), threatening the agricultural economy of relevant Mediterranean crops such as almond (Prunus dulcis). Plant defense elicitor peptides would be promising to manage diseases such as almond leaf scorch but their effect on the host has not been fully studied. In this work, the response of almond plants to the defense elicitor peptide flg22-NH2 was studied in-depth using RNA-seq, confirming the activation of the salicylic acid and abscisic acid pathways. Marker genes related to the response triggered by flg22-NH2 were used to study the effect of the application strategy of the peptide on almond plants and to depict its time course. The application of flg22-NH2 by endotherapy triggered the highest number of upregulated genes, especially at 6 hours after the treatment. A library of peptides that include BP100-flg15, HpaG23, FV7, RIJK2, PIP-1, Pep13, BP16-Pep13, flg15-BP100 and BP16 triggered a stronger defense response in almond plants than flg22-NH2. The best candidate, FV7, when applied by endotherapy on almond plants inoculated with X. fastidiosa, significantly reduced levels of the pathogen and decreased disease symptoms. Therefore, these novel plant defense elicitors are suitable candidates to manage diseases caused by X. fastidiosa, in particular almond leaf scorch.
Project description:We analysed the DNA methylation and transcription levels of transposable elements and genes in leaves of Prunus persica and Prunus dulcis and in their F1 hybrid using high-throughput sequencing tecnhologies. We can conclude that the merging of the two parental genomes in the P. persica x P. dulcis hybrid does not result in a “genomic shock” with significant changes in the DNA methylation or in the transcription.
2022-08-10 | GSE198152 | GEO
Project description:Complete genome resources for two strains of Xylella fastidiosa subsp. sandyi
Project description:Investigation of whole genome gene expression level changes in Xylella fastidiosa 9a5c biofilm, submitted to treatments with sub inhibitory and inhibitory concentrations of copper and tetracycline. A study of Xylella fastidiosa 9a5c was done using total RNA recovered from biofilm bacterial cells submitted to 3 or 7mM of CuSO4 or 100 or 800 µg/ml of tetracycline. Each chip measures the expression level of 2832 genes from Xylella fastidiosa 9a5c with thirteen 60-mer probe pairs (PM/MM) per gene, with five-fold technical redundancy.