Role of a CC-NBS-LRR-like in the Perception/Colonization of Arabidopsis thaliana by Xylella fastidiosa

Xylella fastidiosa is a pathogen bacterium that causes Citrus Variegated Clorosis (CVC) disease in Citrus sinensis (Sweet orange). Due to the economic importance of C. sinensis to Brazil agribusiness, an extensive program for sequencing ESTs for different tissues in response to biotic and abiotic stresses was performed. A database (CitEST) was set in which a total of 38,781 C. sinensis unigenes were assembled. Expression analysis revealed that some of these unigenes could be involved in mandarin (C. reticulata) resistance to X. fastidiosa, being one of them a CC-NBS-LRR-like. To study the function of this gene, we used Arabidopsis thaliana as plant model. Therefore we challenged a CC-NBS-LRR (homologue to mandarin CC-NBS-LRR-like) A. thaliana mutant and WT plants with X. fastidiosa. Bacteria were detected mainly in mutant plants, which showed smaller size compared with WT infected with X. fastidiosa, 10 weeks after inoculation. Besides, we also analyzed the expression of other six genes probably involved in C. reticulata resistance to X. fastidiosa to verify if these genes could be implicated in CC-NBS-LRR-dependent response pathways. The results of this transcription analysis revealed that MOA2.2, a gene encoding a protein with aldolase glycolate oxidase activity, was induced in WT plants infected with X. fastidiosa, but not in mutant plants, while the expression of the other 5 genes did not change. These results suggest that X. fastidiosa is somehow perceived by the CC-NBS-LRR, possibly activating the expression of MOA2.2 in A. thaliana.

Financial Support: FAPESP, CNPq/INCT Citros.