Diffusible signal factor primes plant immunity against pv. () JA signaling in and .

Background: Many Gram-negative bacteria use quorum sensing (QS) signal molecules to monitor their local population density and to coordinate their collective behaviors. The diffusible signal factor (DSF) family represents an intriguing type of QS signal to mediate intraspecies and interspecies communication. Recently, accumulating evidence demonstrates the role of DSF in mediating inter-kingdom communication between DSF-producing bacteria and plants. However, the regulatory mechanism of DSF during the -plant interactions remain unclear.

Methods: Plants were pretreated with different concentration of DSF and subsequent inoculated with pathogen . Pathogenicity, phynotypic analysis, transcriptome combined with metabolome analysis, genetic analysis and gene expression analysis were used to evaluate the priming effects of DSF on plant disease resistance.

Results: We found that the low concentration of DSF could prime plant immunity against in both and . Pretreatment with DSF and subsequent pathogen invasion triggered an augmented burst of ROS by DCFH-DA and DAB staining. CAT application could attenuate the level of ROS induced by DSF. The expression of and were up-regulated and the activities of antioxidases POD increased after DSF treatment followed by Xcc inoculation. Transcriptome combined with metabolome analysis showed that plant hormone jasmonic acid (JA) signaling involved in DSF-primed resistance to in Arabidopsis. The expression of JA synthesis genes ( and ), transportor gene (), regulator genes ( and ) and responsive genes ( and ) were up-regulated significantly by DSF upon Xcc challenge. The primed effects were not observed in JA relevant mutant and .

Conclusion: These results indicated that DSF-primed resistance against was dependent on the JA pathway. Our findings advanced the understanding of QS signal-mediated communication and provide a new strategy for the control of black rot in .