AiiA-mediated quorum quenching does not affect virulence or toxoflavin expression in Burkholderia glumae SL2376

Aim: The primary objective of this study was to determine the effects of quorum quenching in the pathogenicity and toxoflavin production of Burkholderia glumae causing bacterial rice grain rot. Methods and Results: An acyl-homoserine lactonase (aiiA) gene from Bacillus sp. was expressed in B. glumae under the control of a constitutive promoter. Acyl-homoserine lactone production in the aiiA-transformants was reduced significantly, and the aiiA-expressing B. glumae strain reduced the severity of soft rot when the strain was co-inoculated with a soft-rot pathogen, Pectobacterium carotovorum ssp. carotovorum SCCI. However, the aiiA-transformant still caused rice seedling rot and rice grain rot. The aiiA-expressing strains had wild-type levels of transcription from the genes in the toxoflavin biosynthetic operon, and as well as wild-type levels of toxin production. Conclusions: Our results show that aiiA-mediated quorum quenching does not affect virulence or toxoflavin production in B. glumae. Significance and Impact of the Study: Indirect quorum quenching may prove an ineffective approach to the control of rice grain rot, because it reduces, but does not eliminate entirely homoserine lactones in B. glumae. Virulence of rice grain rot was retained despite reduction in homoserine lactones by the expression of aiiA in B. glumae.