BioProject

Plant defense responses to biotic stresses are complex biological processes, all governed by sophisticated molecular regulations. More...

Plant defense responses to biotic stresses are complex biological processes, all governed by sophisticated molecular regulations. Induced systemic resistance (ISR) is one of these defense mechanisms where beneficial bacteria or fungi prime plants to resist pathogen or pest attacks. In ISR the defense arsenal in plants remains dormant and it is only triggered by the infection, allowing a rapid response and a better allocation of plant resources. We recently described that the well-known beneficial bacterium Paraburkholderia phytofirmans PsJN is able to reduce Arabidopsis thaliana susceptibility to Pseudomonas syringae Pst DC3000 through ISR. Nevertheless, the molecular networks governing this beneficial interaction remain unknown. To tackle this issue we analyzed the temporal changes in the transcriptome of PsJN-inoculated plants before and after the infection with Pst DC3000 strain. These data were used to perform a gene network analysis to identify highly connected transcription factors that may be acting as hubs in controlling this ISR response. Before the pathogen challenge, strain PsJN regulated 405 genes (corresponding to 1.5% of the analyzed genome). PsJN-inoculated plants presented a faster and stronger transcriptional response 1-hour post infection (hpi) compared with the non-inoculated plants, which presented the highest transcriptional changes 24 hpi. A principal component analysis showed that PsJN-induced plant responses to the pathogen could be differentiated from those induced by the sole pathogen. Forty-eight transcription factors were regulated by PsJN 1 hpi, and a system biology analysis revealed a network with 4 modules where LHY, WRKY28, MYB31 and RRTF1 are highly connected transcription factors, that can be acting as hub regulators in this interaction. These modules are related to Jasmonate, Ethylene, Salicylic acid and ROS pathways. Additionally, the down- and up-regulation of ANAC32 and ORA59, respectively, support an important role of PDF1.2. These results indicate that a rapid and specific response of PsJN-inoculated plants to this virulent pathogen could be the pivotal element in the protection mechanism. A role for specific transcriptional regulators in the orchestration of this complex molecular response is also proposed Overall design: Transcriptome-profiling assay using non-inoculated plants and strain PsJN-inoculated (0 hpi) plants was performed. Additionally, the analyses included samples 1 and 24 h after a challenge with P. syringae Pst DC3000 (1 and 24 hpi) Less...