Comparative proteomic analysis provides insight into the key proteins involved in novel stem-physical-strength-mediated resistance (SPSMR) mechanism against Sclerotinia sclerotiorum in Brassicaceae

Sclerotinia sclerotiorum stands out as the most destructive pathogen affecting oilseed Brassica crops. Our study unveils the proteomic basis of a novel resistance mechanism, termed "Stem-Physical-Strength-Mediated-Resistance (SPSMR)," against S. sclerotiorum in Brassicaceae through a comparative proteomic analysis. Field assessments highlight significant differences in stem-physical strength attributes between the resistant (R) and susceptible (S) genotypes, emphasizing the importance of SPSMR. Field evaluation revealed that the resistant genotype S. alba SA1 demonstrates significantly (P ≤ 0.01) superior stem traits at various time points post-inoculation as compared to susceptible genotypes. Pearson's correlation analysis establishes significant associations between lesion length and stem attributes, with stem breaking strength emerging as a key contributor to resistance. Proteomic profiling at different infection stages reveals temporal dynamics, showcasing the resistant genotype's robust and adaptive defense response. KEGG enrichment analysis underscores the significance of phenylalanine metabolism and phenylpropanoid biosynthesis pathways. Differentially Expressed Proteins (DEPs) in resistant and susceptible genotypes revealed intricate expression profiles, particularly in lignin biosynthesis. Proteins associated with cell wall fortification, especially in the lignin biosynthetic pathway, exhibit nuanced expression profiles. Specific proteins, including phenylalanine ammonia-lyase, shikimate dehydrogenase, cinnamyl alcohol dehydrogenase 5, and peroxidase, show significantly higher expression in the resistant genotype across infection stages. Additionally, proteins involved in plant-pathogen, intracellular pH regulation, and antioxidant defense exhibit differential expression, contributing to a comprehensive understanding of the complex regulatory network during S. sclerotiorum infection. This research not only enhances our understanding of the molecular mechanisms underlying resistance but also underscores the varied strategies utilized by Brassicaceae to combat pathogenic intrusion, emphasizing the potential for developing resistant cultivars against S. sclerotiorum.