The Transcription Factor Lrp of subsp. Controls Capsule Production, Motility, and Virulence Important for Growth.

The bacterial phytopathogen subsp. causes leaf blight and Stewart's wilt disease in susceptible corn varieties. A previous RNA-Seq study examined gene expression patterns during late-stage infection in the xylem, and a Tn-Seq study using a mutant library revealed genes essential for colonization of the xylem. Based on these findings, strains with in-frame chromosomal deletions in the genes encoding seven transcription factors (NsrR, IscR, Nac, Lrp, DSJ_00125, DSJ_03645, and DSJ_18135) and one hypothetical protein (DSJ_21690) were constructed to further evaluate the role of the encoded gene products during and growth. Assays for capsule production and motility indicate that Lrp plays a role in regulating these two key physiological outputs . Single infections of each deletion strain into the xylem of corn seedlings determined that Lrp plays a significant role in virulence. xylem competition assays between co-inoculated deletion and the corresponding complementation or wild-type strains as well as growth curves determined that Lrp controls functions important for colonization and growth in corn plants, whereas IscR may have a more generalized impact on growth. Defining the role of essential transcription factors, such as Lrp, during growth will enable modeling of key components of the regulatory network utilized during growth in corn plants.