Comparative Transcriptomic Analysis Reveals Cultivar-Dependent Resistance Responses to Pseudomonas tolaasii in...

Pseudomonas tolaasii, the causal agent of bacterial brown blotch disease, is a major threat to the yield and quality of oyster mushroom (Pleurotus ostreatus). To investigate the molecular basis of cultivar-dependent resistance, we performed comparative transcriptome analysis using the resistant cultivar 'Aenutari' (KMCC01220; AE) and the susceptible cultivar 'Dahyun' (KMCC04942; DH) under P. tolaasii challenge. The two cultivars showed contrasting phenotypic and transcriptomic responses after pathogen inoculation. DH exhibited visible disease symptoms and severe mycelial growth inhibition, with relative mycelial growth reduced to 33.97 ± 2.53% of the control, whereas AE maintained a relatively resistant phenotype and higher mycelial growth under pathogen challenge, reaching 51.19 ± 3.72% of the control. Consistent with these phenotypic differences, DH showed extensive transcriptional reprogramming, with 3585 up-regulated and 4377 down-regulated differentially expressed genes (DEGs). In contrast, AE showed a much narrower transcriptional response, with 181 up-regulated and 71 down-regulated DEGs. Functional enrichment analysis indicated that pathogen-responsive DEGs in AE were mainly associated with carbohydrate metabolism, extracellular regions, redox-related processes, and ion transport. In cultivar-wise comparisons under pathogen-inoculated conditions, genes highly expressed in AE were enriched in RNA splicing, mRNA processing, mitochondrial organization, mitochondrial gene expression, transmembrane transport, oxidoreductase activity, and sterol-related metabolism. These results indicate that the resistant phenotype of AE is associated with a more limited pathogen-induced transcriptional perturbation and the relative enrichment of gene modules related to RNA processing, mitochondrial organization and gene expression, membrane transport, redox-related processes, and sterol metabolism. This study provides a transcriptomic framework for understanding cultivar-dependent responses to bacterial brown blotch disease in oyster mushroom.