Structural basis of a novel repressor, SghR, controlling Agrobacterium infection by cross-talking to plants

Abstract

<jats:p><jats:italic>Agrobacterium tumefaciens</jats:italic> infects various plants and causes crown gall diseases involving temporal expression of virulence factors. SghA is a newly-identified virulence factor enzymatically releasing salicylic acid from its glucoside conjugate and controlling the plant tumor development. Here we report the structural basis of SghR, a LacI-type transcription factor and highly conserved in Rhizobiaceae family, regulating the expression of SghA and involved in tumorigenesis. We identified and characterized the binding site of SghR on the promoter region of <jats:italic>sghA</jats:italic>, and then determined the crystal structures of apo-SghR, SghR complexed with its operator DNA and ligand sucrose, respectively. These results provide detailed insights into how SghR recognizes its cognate DNA and shed a mechanistic light on how sucrose attenuates the affinity of SghR with DNA to modulate the expression of SghA. Given the important role of SghR in mediating the signaling crosstalk during <jats:italic>Agrobacterium</jats:italic> infection, our results pave the way for structure-based inducer analogue design, which has potential applications for agricultural industry.</jats:p>

Molecular basis of the key regulator WRINKLED1 in plant oil biosynthesis

“…Comparison of our structure with that of the DNA-bound Plasmodium falciparum transcription factor SIP2, which contains two AP2 domains [Protein Data Bank (PDB) ID: 6SY0], revealed that SIP2 uses an - turn, rather than the  sheet observed in AtWRI1, for specific DNA recognition that is quite common as indicated in our recently described SghR (salicylic acid -glucoside hydrolase repressor)-DNA structure (Fig. 3A) (42). The domain organization of SIP2 was also significantly different from that of AtWRI1, particularly in the domain linker region (Fig.…”

Mechanisms of Virulence Reprogramming in Bacterial Pathogens

“…Wang et al (131) recently found that A. tumefaciens can produce a SAG hydrolase, SghA, to hydrolyze SAG in order to release SA. In the free-living or nonpathogenic stage, SghA is not synthesized because of tight control by the negative regulator protein SghR, which binds directly to the promoter of sghA and suppresses its expression (131,142). In contrast, during infection this binding effect is reversed by the accumulated plant disaccharide sucrose, which is stimulated by wounding and microbial infection (25).…”