HOMOLOGY OF SEVERAL GENES INVOLVED IN HARPIN SECRETION WITH YOP SECRETION GENES IN YERSINIA

Harpin is an extracellular protein crucial to the pathogenicity and HR (hypersensitive response) eliciting ability of Erwinia amylovora. Synthesis and export of harpin depends on a 40 kb chromosomal cluster of hrp genes.
We have determined that a 10.5 kb portion of the cluster required for harpin secretion contains eleven genes including hrpl, published previously.
Downstream of hrpl are eight genes with extensive similarity to Yersinia secretion genes yscN-U. These genes are involved in the export of virulence proteins called Yops and are homologous with virulence factor export genes of other pathogenic bacteria and with flagellar biosynthesis genes.
The E. amylovora genes were named hrcN, hrpO, hrpP, hrcQ, hrcR, hrcS, hrcT, and hrcU. A mutant strain with an in-frame deletion in hrcT failed to secrete harpin and was hrp^–. Immediately downstream of hrpl, we found a homolog of yscD, also involved in Yop export, which we have named hrcD. Immediately upstream of hrpl, we found a homolog of yopN, which we named hrpU. YopN is a surface protein that plays a key role in the cell-contact-triggered expression and transfer of YopE to the cytoplasm of the mammalian target cell.
Our results reveal the striking similarity in a large number of virulence-associated genes that function in the secretion of proteins by Yersinia and Erwinia, two very distinct pathogens.

VII International Workshop on Fire Blight

A.J. Bogdanove, Z.-M. Wei, L. Zhao, S.V. Beer

https://doi.org/10.17660/ActaHortic.1996.411.51