Enhanced Resistance to Sclerotinia sclerotiorum in Brassica rapa by Activating Host Immunity through Exogenous Verticillium dahliae Aspf2-like Protein (VDAL) Treatment

Abstract

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most destructive diseases in Brassica rapa. Verticillium dahliae Aspf2-like protein (VDAL) is a secretory protein of V. dahliae which has been shown to enhance the resistance against fungal infections in several plants. Nonetheless, the molecular mechanisms of VDAL-primed disease resistance are still poorly understood. In this study, we performed physiological, biochemical, and transcriptomic analyses of Brassica rapa in order to understand how VDAL confers resistance to S. sclerotiorumn infections in plants. The results showed that foliar application of VDAL significantly reduced the plaque area on leaves inoculated with S. sclerotiorum. It also enhanced antioxidant capacity by increasing activities of superoxide dismutase (SOD), peroxidase (POD), peroxidase (APX), glutathione reductase (GR), protoporphyrinogen oxidase (PPO), and defense-related enzymes β-1,3-glucanase and chitinase during the infection periods. This occurred in parallel with significantly reduced relative conductivity at different periods and lower malondialdehyde (MDA) content as compared to sole S. sclerotiorum inoculation. Transcriptomic analysis showed a total of 146 (81 up-regulated and 65 down-regulated) differentially expressed genes (DEGs) in VDAL-treated leaves compared to the control. The most enriched three Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were the mitogen–activated protein kinase (MAPK) signaling pathway, plant hormone signal transduction, and plant-pathogen interaction, all of which were associated with plant immunity. DEGs associated with MAPK and hormone signal transduction pathways were ethylene response sensor ERS2, EIN3 (Ethylene Insensitive3)-binding F-box protein 2 (EBF2), ethylene-responsive transcription factor ERF94, MAPK 9 (MKK9), protein phosphatase 2C (PP2C37), auxin-responsive proteins (AUX/IAA1 and 19), serine/threonine-protein kinase CTR1, and abscisic acid receptors (PLY 4 and 5). Among the DEGs linked with the plant–pathogen interaction pathway were calmodulin-like proteins (CML5, 24, 27), PTI1-like tyrosine protein kinase 3 (Pti13) and transcription factor MYB30, all of which are known to play key roles in pathogen-associated molecular pattern (PAMP)-triggered immunity and effector-triggered immunity (ETI) for hypersensitive response (HR), cell wall reinforcement, and stomatal closure in plants. Overall, VDLA treatment triggered repression of the auxin and ABA signaling pathways and de-repression of the ethylene signaling pathways in young B. rapa seedlings to increase plant innate immunity. Our results showed that VDAL holds great potential to enhance fungal disease resistance in B. rapa crop.

Fungal effectors versus defense-related genes of B. juncea and the status of resistant transgenics against fungal pathogens

“…It was also used for host-induced gene silencing control of the disease. Foliar application of Verticillium dahliae Aspf2 -like protein induced many defense-related compounds in B. rapa and possessed a great ability to increase the SSR resistance ( Jiang et al., 2022 ). In angiosperms, guaiacyl monolignol is converted to syringyl monolignol with the help of Ferulate-5-hydroxylase.…”

Unveiling the Molecular Basis of Stem-Physical-Strength-Mediated-Resistance (SPSMR) Mechanism Against Sclerotinia sclerotiorum in Brassicaceae: A Comparative Transcriptome Analysis of Resistant and Susceptible Genotypes

“…In addition to identifying effective and highly resistant sources, extensive research has been conducted to elucidate the resistance mechanisms employed by Brassicaceae plants against S. sclerotiorum. Induced systemic resistance (ISR) is one such mechanism, where plants enhance their resistance through exposure to bene cial microbes or plant growth-promoting substances Alkooranee et al, 2017;Jiang et al, 2022). Phytoalexins, such as glucosinolates and their breakdown products, produced by certain Brassicaceae species effectively hinder the growth of S. sclerotiorum Madloo et al, 2019;Abuyusuf et al, 2018).…”