Extracellular Compounds from Pathogenic Bacterium <i>Pseudoalteromonas piscicida</i> X-8 Cause Bleaching Disease, Triggering Active Defense Responses in Commercially Farmed <i>Saccharina japonica</i>

Abstract

Pathogenic bacteria can trigger active defense responses in higher plants, leading to hypersensitive programmed cell death (PCD) to against those bacteria. However, related research on seaweeds is very limited. Pseudoalteromonas piscicida X-8 (PpX-8) has been identified as the pathogen that causes bleaching disease in commercially farmed Saccharina japonica. In this study, using an inoculation assay and microscopic observations, we found that the proportion of bleaching tissue pieces inoculated with PpX-8 extracellular compounds was significantly higher (p S. japonica. These results indicate that seaweeds and higher plants are conservative in their active defense responses against pathogenic bacteria. The results of this study lay the foundation for further investigation of the virulence mechanisms of PpX-8.

Keywords

• active defense responses
• bleaching disease
• <i>Saccharina japonica</i>
• programmed cell death
• <i>Pseudoalteromonas piscicida</i> X-8