Putative secreted proteins of Candidatus Liberibacter asiaticus are localized in specific cellular compartments and trigger different responses in plants.

MOLINA M.C.; AGOSTINI J.P.; MARANO M.R.; GARCIA L.; REDES J.; GADEA J.; TORRES P.S.; VOJNOV A.

Orlando

Congreso; V International Research Conference on Huanglongbing.; 2017

IOCV, Organization

Candidatus Liberibacter asiaticus (Las), the most prevalent causal agent of huanglongbing citrus disease in North America and Asia, is a phloem- limited and unculturable bacterium. However, during the past few years, genomes of several Liberibacter species were sequenced suggesting that members of this genus have suffered a significantly genome reduction. Comparative genomics of Las has allowed the prediction of the putative effector proteins, potentially involved in virulence. In this scenery, where small secreted protein could play crucial roles between plant and pathogen interaction, effector proteins identification is a complex objective. Plant defense can be triggered by the host perception of conserved pathogen-associated molecular patterns (PAMPs). Pathogens in turn can suppress PAMP-triggered immunity, causing disease. Identification of Las effector proteins is a key step to understand the mechanisms by which Las disrupt the host response. To provide a functional basis for this hypothesis, eight of these sequences were cloned and expressed fused to green or red fluorescent proteins under the control of 35S promoter. Agrobacterium-mediated transient expressions were performed in Nicotiana tabacum and N. benthamiana leaves. Bacterial protein expressions were monitored over a 10-day period by fluorescence and confocal laser scanning microscopy. All tested genes shown expression in plant cells, and revealed different subcellular distribution patterns respect to the control. Expression of two of them produced particular phenotypes in plants. CLIBASIA_04560 encoded a hypothetical protein which is localized in nucleus when it is transiently expressed in N. benthamiana. More interesting, this protein triggers an increase of H2O2 production respect to the control without necrotic or cell death phenotype in N. benthamiana after 3 dpi. Now, we are studying if Clibasia_04560 may act as an effector protein modulated the energetic metabolism in citrus plants.