Conserved genetic defense response against X. fastidiosa subsp. pauca in olive and citrus

X. fastidiosa subsp. pauca causes diseases in citrus and olive plants. Fortunately, there are
citrus species and olive varieties more tolerant to X. fastidiosa and therefore good genotypes to
search for genetic sources of resistance. Following this approach, global gene expression analyses
were recently achieved using Citrus reticulata cv. Ponkan and Olea europaea cv. Leccino allowing the
identification of potential genes involved in plant defense response. Thus, the objective of this work
was to identify key genes involved in common genetic defense responses that could be further
explored to get resistant varieties. Overall we identified two main mechanisms for both plant species:
i. Bacteria recognition and ii. Cell wall fortification. The former involve the expression of patternrecognition receptors, which recognize pathogen molecular patterns and trigger cell defense
responses. Some of these receptors belong to the LRR-XII group which contains cell surface immune
receptors. The latter involves downregulation of genes in tolerant host such as expansin, pectate
lyases and polygalacturonases, related with cell wall expansion and degradation. This suggests that in
tolerant hosts, plant cell recognizes X. fastidiosa and reprograms the cell wall development to impair
its colonization through the xylem vessels. Therefore these genes represent good candidates to be
explored aiming their use in breeding and/or genetic engineering program.
 

Giampetruzzi A., Morelli M., Saponari M., Loconsole G., Chiumenti M., Boscia D., Savino V.N., Martelli
G.P. & Saldarelli P. 2016. Transcriptome profiling of two olive cultivars in response to infection by
the CoDiRO strain of Xylella fastidiosa subsp. pauca. BMC Genomics 17:475.
Rodrigues C.M., De Souza A.A., Takita M.A., Kishi L.T. & Machado M.A. 2013. RNA-Seq analysis of
Citrus reticulata in the early stages of Xylella fastidiosa infection reveals auxin-related genes as a
defense response. BMC Genomics 14: 676.