Reveals Defense Pathways in Chinese Cabbage Against Black Spot Disease 🌱🧬 #pencis #researchawards

Introduction

Black spot disease, caused by Alternaria brassicicola, represents a major biotic constraint to Chinese cabbage production, leading to significant yield and quality losses. Understanding the molecular and biochemical defence strategies employed by resistant germplasm is essential for developing durable disease management approaches. Recent advances in multi-omics technologies have enabled integrated analyses of transcriptomic and metabolomic responses during early pathogen infection, offering new insights into host–pathogen interactions. In this context, the Chinese cabbage line 904B provides an excellent model to dissect early defence signalling and resistance-associated pathways against black spot disease.

Hormonal Reprogramming During Early Infection

Upon infection with A. brassicicola, Chinese cabbage line 904B exhibits a pronounced shift in phytohormone signalling. Growth-related hormones such as cytokinin and auxin are significantly suppressed, reflecting a strategic reallocation of resources away from development toward defence. In contrast, defence-associated hormones, particularly ethylene and jasmonic acid (JA), are strongly activated. This hormonal reprogramming highlights the central role of JA–ethylene crosstalk in mediating resistance to necrotrophic pathogens and underscores the importance of hormone balance in early immune responses.

Transcriptomic Insights Into Defence Activation

Transcriptomic profiling at 24 hours post-inoculation reveals extensive gene expression reprogramming in 904B. Genes involved in signal transduction, reactive oxygen species (ROS) production, and stress responses are markedly upregulated, while those associated with cell growth and differentiation are downregulated. Notably, defence-related kinases and transcriptional regulators show rapid induction, suggesting a tightly controlled signalling cascade that enables rapid perception of pathogen invasion and activation of downstream immune responses.

Metabolomic Remodeling and Secondary Metabolites

Metabolomic analysis demonstrates significant alterations in secondary metabolite accumulation following pathogen challenge. Among these, the sterol compound 4,4-dimethyl-5α-cholest-7-en-3β-ol is markedly upregulated in infected tissues, implicating sterol metabolism in plant defence. Differentially accumulated metabolites are primarily enriched in indole alkaloid metabolism and glycerolipid metabolism pathways, indicating their involvement in strengthening cellular barriers, modulating membrane integrity, and enhancing antimicrobial activity during black spot disease resistance.

Functional Role of BraPBL in Disease Resistance

BraPBL, a receptor-like cytoplasmic kinase (RLCK) family member, exhibits progressively increased expression with prolonged A. brassicicola infection. Functional analyses demonstrate that overexpression of BraPBL significantly enhances resistance to black spot disease, whereas gene silencing compromises host defence. Subcellular localization studies confirm that BraPBL resides at the plasma membrane, consistent with its proposed role in early pathogen perception and signal initiation.

BraPBL-Mediated Signalling and Defence Pathways

Overexpression of BraPBL leads to the activation of key defence-associated genes, including the ROS-generating enzyme RBOH and the mitogen-activated protein kinase kinase kinase MEKK1. This activation promotes ROS accumulation and signal amplification, while simultaneously stimulating the JA signalling pathway. Collectively, these findings position BraPBL as a crucial positive regulator of black spot disease resistance, linking membrane-associated signalling, hormone-mediated defence, and metabolic reprogramming in Chinese cabbage.

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Hashtags

#BlackSpotDisease, #ChineseCabbage, #AlternariaBrassicicola, #PlantPathology, #PlantImmunity, #Transcriptomics, #Metabolomics, #Phytohormones, #JasmonicAcid, #EthyleneSignaling, #SecondaryMetabolites, #SterolMetabolism, #BraPBL, #RLCK, #ROS, #MAPKSignaling, #DiseaseResistance, #HostPathogenInteraction, #PlantDefenseMechanisms, #CropProtection