Nicole Wicker, “The Starvation Sensing Protein RspB Alters pel Expression in High C-di-GMP Condition in D. dadantii”
Mentors: Ching-Hong Yang & Biswarup Banerjee, Biological Sciences

Dickeya dadantii is a phytopathogenic bacterium with a wide host range. PelD, an endopectatelyase enzyme secreted by D. dadantii through the type II secretion system, degrades the cell wall in host plants. The second messenger cyclic diguanylate monophosphate (c-di-GMP) has been reported to regulate the expression of virulence genes in D. dadantii. EcpC is a phosphodiesterase that hydrolyzes c-di-GMP in D. dadantii, thus lowering the intracellular c-di-GMP concentrations. A low PelD expression is observed under the ecpC mutant background (high c-di-GMP). In order to elucidate the c-di-GMP effectors that regulate PelD production, a transposon library was made under ecpC mutant background. Mutants were screened by analyzing the expression of PelD. Those with an increased pelD promoter activity were selected for further investigation. One of the genes mutated by the transposon was identified to be rspB by sequencing. The rspB supposedly is starvation sensing protein as per annotation. Probably rspA-rspB operon functions together for regulating downstream gene expressions. In Escherichia coli K12 strain this gene has been reported to regulate multiple virulence factor genes. Future work will explore the role of RspB in regulating type II, type III secretion systems and connect the role of c-di-GMP in these regulatory pathways.

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