Uncovering Candidate Pathogenicity Genes in Erwinia pyrifoliae YKB12327 via Tn5-insertion Mutagenesis

<i>Erwinia pyrifoliae</i> is a gram-negative bacterial pathogen that commonly causes black shoot blight in pear and apple tree. Although the pathogenicity of this bacterial species is very similar to <i>E. amylovora</i>, there is no specific explanation of its pathogenic genes and mechanisms. In this study, our investigation into <i>E. pyrifoliae</i> pathogenicity involved generating seven YKB12327 mutant strains using Tn5 transposon mutagenesis. Observations revealed weakened growth rate and loss of pathogenicity in these mutants. Whole-genome sequencing and alignment analysis identified transposon insertions within the coding sequences of five strains and in the intergenic region of two strains. Annotation analysis elucidated genes directly or indirectly associated with pathogenicity. Notably, mutant strain MT16 displayed a transposon insertion mutation in the cyclic-di-GMP phosphodiesterase (<i>pdeF</i>) gene, a key player in bacterial signaling, governing microbial behavior and adaptation to environmental changes. Our findings provide insights into the genetic regulation of <i>E. pyrifoliae</i> pathogenicity, suggesting potential avenues for further research aimed at understanding and controlling this bacterial pathogen by targeting <i>pdeF</i> to mitigate apple black shoot blight disease.