Infections of the Xylella fastidiosa subsp. pauca Strain "De Donno" in Alfalfa ( Medicago sativa ) Elicits an Overactive Immune Response

• Published in: Plants (Basel) 2019-09, Vol.8 (9), p.335
• Main Authors: Abou Kubaa, Raied, Giampetruzzi, Annalisa, Altamura, Giuseppe, Saponari, Maria, Saldarelli, Pasquale
• Format: Article
• Language: English
• Subjects: Alfalfa; Biofilms; Calcium; Cell death; Dwarf disease; Epidemiology; Experiments; Flowers & plants; Gene expression; Genes; Genomes; Genomics; Host plants; Immune response; Immune system; Infections; Kinases; Latent period; medicago; Medicago sativa; Necrosis; olive; Olives; Pathogens; pauca; Plant bacterial diseases; Plant diseases; Plant immunity; Principal components analysis; Proteins; Reactive oxygen species; Research programs; Signs and symptoms; transcriptome; Virulence; Xylella; Xylella fastidiosa
• ISSN: 2223-7747; 2223-7747
• DOI: 10.3390/plants8090335

Diseases caused by are among the most destructive for several agricultural productions. A deadly disease of olive, termed olive quick decline syndrome, is one of the most recent examples of the severe impacts caused by the introduction and spread of this bacterium in new ecosystems with favorable epidemiological conditions. Deciphering the cascade of events leading to the development of severe alterations in the susceptible host plants is a priority of several research programs investigating strategies to mitigate the detrimental impacts of the infections. However, in the case of olives, the long latent period (>1 year) makes this pathosystem not amenable for such studies. We have inoculated alfalfa ( ) with the olive-infecting strain "De Donno" isolated from a symptomatic olive in Apulia (Italy), and we demonstrated that this highly pathogenic strain causes an overactive reaction that ends up with the necrosis of the inoculated stem, a reaction that differs from the notoriously Alfalfa Dwarf disease, caused by strains isolated from grapes and almonds. RNASeq analysis showed that major plant immunity pathways are activated, in particular, several calcium transmembrane transporters and enzymes responsible for the production of reactive oxygen species (ROS). Signs of the necrotic reaction are anticipated by the upregulation of genes responsible for plant cell death and the hypersensitive reaction. Overall the whole infection process takes four months in alfalfa, which makes this pathosystem suitable for studies involving either the plant response to the infection or the role of genes in the expression of symptoms.