Time series RNA-seq reveals early root responses to ISR-inducing Pseudomonas simiae WCS417 and the microbial elicitors flg22, flg22417, and chitin.
I. STRINGLIS (1), S. Proietti (2), M. van Verk (2), R. Hickman (2), C. Zamioudis (2), C. Pieterse (2) (1) Utrecht University, Netherlands; (2) Utrecht University, Netherlands

The ability of roots to discriminate between pathogenic and beneficial microbes is crucial for plant health. In Arabidopsis, beneficial Pseudomonas simiae WCS417 rhizobacteria trigger an induced systemic resistance (ISR) that is effective against a broad range of pathogens. The early responses activated in the roots upon perception of WCS417 are largely unknown. Here, we used time-series RNA-seq to compare the early root responses to living WCS417 with that of the bacterial and fungal elicitors flagellin (flg22 of P. aeruginosa and flg22417 of WCS417) and chitin, respectively. Our data show that the early transcriptional root responses to flg22 and chitin differ in timing, but display a large overlap in gene identity. The majority of the upregulated genes are involved in immunity, while the downregulated genes are predominantly related to development. Interestingly, the transcriptional response of roots to flg22 was highly similar to flg22417, despite the 5 amino acids differing between the two peptides. Even though 83% of the transcriptional changes inflicted by living WCS417 overlapped with the flg22417 profile, 50% of the flg22417 profile was not affected by living WCS417. These findings suggest that WCS417 is recognized as a potential attacker, but that a large part of the flagellin-triggered response is swiftly suppressed, possibly to overcome host immunity in order to establish a mutually beneficial interaction.

Abstract Number: P1-2
Session Type: Poster