Pantoea agglomerans YS19 is a dominant endophytic bacterium isolated from rice, which is capable of promoting host plant growth by nitrogen-fixing and phytohormone secreting. We previously found that the cytidine repressor (CytR) protein conducts the regulation of indole signal in YS19. Here, we compared the whole-cell protein of the wild type YS19 and the ΔcytR mutant and subsequently identified one differential protein as alkyl hydroperoxide reductase subunit C related to oxidative stress and

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... sulfur starvation tolerance. It was tested that cytR had a positive effect on the survival of YS19 under the oxidative stress and sulfur starvation conditions and this effect was inhibited by indole. To further understand the functional mode of indole in this regulation, we cloned the cytR promoter region (PcytR) of YS19 and tested the effect of indole on PcytR using gfp as a reporter gene. It was found that PcytR can sense indole and significantly inhibit the expression of the downstream gene. This study provided a deeper understanding of the multiple function of cytR and expanded a new research direction of how indole participates in gene regulation.