Fig 4.

Cross talk between all the SPIs. The regulatory effects which may be explained through an indirect pathway have not been represented to make comprehension easier (i.e., the effects that HilD, HilC, HilE, PhoQ-PhoP, and SirA-BarA exert on either SPI-4 or SPI-5). According to the evidence reported in the text, the regulators marked with an asterisk are those proposed to act in this model on the SPI-2 genes via SsrA-SsrB. The roles reported for Lon and DnaK regarding systemic virulence have not been included in this model, since there is no specific information about their target genes. (A) Regulators positively influencing expression of the SPI genes. (B) Regulators leading to a repressor effect.