Differential analyses of morphology and transcription from oyster mushroom Pleurotus ostreatus response to brown blotch disease

Abstract

Pleurotus ostreatus is among the most frequently cultivated and consumed mushrooms worldwide. However, brown blotch disease (BBD) caused by the pathogenic bacterium Pseudomonas tolaasii severely impacted its quality and production. In this study, we selected the BBD-resistant strain HP36 and the BBD-sensitive strain HP801 from twenty P. ostreatus strains. Obvious morphological and ultrastructural differences between the two strains were observed at 12 h, 24 h and 72 h after Ps. tolaasii infection. At 24 h, a large area of brown-yellow blotch appeared on the pileus of HP801 and with Ps. tolaasii almost completely overgrowing the pileus. In contrast, few bacteria and no obvious symptoms were found on the pileus of HP36. At 72 h, the cell wall and nuclei and mitochondria were seriously damaged in HP801 while no obvious deformity was observed in HP36. In the infected pileus, transcriptome analysis identified 153 and 2,189 differentially expressed genes for HP36 and HP801 respectively. Further bioinformatic analysis showed that genes encoding oxidation–reduction enzymes, cell wall degradation, heat shock proteins and protein kinases were significantly more differentially expressed after infection in HP801 than in HP36. The results suggested that Ps. tolaasii infection impaired the capacities of HP801 for stress sensing and signal transduction, oxidation resistance and protein modification, resulting in cellular and organelle damages. Together, our results provided insights into the molecular mechanism of resistance to BBD in P. ostreatus and suggested potential strategies for controlling BBD and improving mushroom production and quality by selecting and breeding the resistant strains.