The RNA-Binding Protein ProQ Impacts Exopolysaccharide Biosynthesis and Second Messenger Cyclic di-GMP Signaling in the Fire Blight Pathogen Erwinia amylovora

Abstract

Fire blight, caused by the bacterium Erwinia amylovora , is an important disease affecting many rosaceous plants, including apple and pear, that can lead to devastating economic losses worldwide. Similar to many xylem-invading pathogens, E. amylovora forms biofilms that rely on the production of exopolysaccharides (EPSs).

FinO/ProQ-family proteins: an evolutionary perspective

“…Such structural elements are naturally rife in intrinsic terminators of bacterial transcripts. Indeed, most known RNA partners of FinO/ProQ-family proteins engage the protein via their terminator structures ( Figures 1 and 2 ), which was confirmed by both focused studies in vitro and by global interactomic profiling of ligands in vivo [ 4 , 33 , 36 , 37 , 39 , 40 , 46 , 48 , 49 , 58 ]. However, a few prominent processed ProQ ligands, such as certain phage-encoded and intragenic sRNAs, are devoid of terminators and appear to interact via other similarly structured elements [ 3 , 36 , 62 ].…”

“…For example, E. coli and D. dadantii ProQ proteins are involved in resistance to osmotic stress [ 45 , 74 ], but this role is not conserved in P. multocida [ 48 ]. Whereas in E. coli and P. luminescens ProQ positively regulates biofilm formation [ 38 , 47 ], its effect is opposite in the closely related E. amylovora and D. dadantii [ 45 , 46 ], and null in the phylogenetically distant N. meningitidis [ 49 ].…”

“…The sources of this functional divergence are likely both extrinsic (i.e. linked to differences in transcriptomes between species and even between growth conditions for the same species [ 3 , 36 , 37 , 39 , 46 , 48 , 49 , 72 ]) and intrinsic (i.e. stemming from the proteins themselves).…”

Exopolysaccharides amylovoran and levan contribute to sliding motility in the fire blight pathogen Erwinia amylovora

“…Deletion mutants of flhDC1 , motA1 , fliC , amsG , amyR , and lsc were constructed using the red recombinase method (Datsenko & Wanner, 2000 ), and the method was recently described elsewhere (Yuan et al, 2022 ). Complementation strains were constructed by cloning the putative promoter and open reading frame (ORF) regions of target genes into the plasmid pBBR1‐MCS5 (Table 1 ), followed by electroporation of the resulting plasmids into E. amylovora .…”

“…Apple shoot virulence and levansucrase activity assays were performed as recently described (Yuan et al, 2022 ). Amylovoran production was determined in supernatants of bacterial cultures using a turbidity assay with cetylpyrimidinium chloride (CPC) (Bellemann et al, 1994 ).…”