Identification and characterization of a novel Haematococcus pluvialis strain resistant to Paraphysoderma sedebokerense infection

The commercial culture of Haematococcus pluvialis is threatened by the pathogen Paraphysoderma sedebokerense, leading to substantial losses in the natural astaxanthin industry. This study successfully identified a novel H. pluvialis strain WBG-26, which exhibited high resistance to P. sedebokerense in both laboratory and open raceway ponds. Comparative analysis showed that the resistant strain WBG-26 had a thicker cell wall and lower levels of specific monosaccharides which may be closely related to resistance. RNA-sequencing analysis revealed differential gene expression profiles, with 29 up-regulated and 25 down-regulated genes identified as crucial for resistance. Using bioinformatics analysis, we identified several potential resistance genes and resistance-related genes, such as those encoding receptor-like kinases, leucine-rich repeat, transcription factors, CAZymes, and heat shock proteins, which may play critical roles in defense response. This study represents a comprehensive investigation of multiple defense mechanisms of microalgae, providing insights into breeding disease-resistant microalgal strains for biotechnological applications.