Comparative Analysis of Temporal Transcriptome Reveals the Relationship Between Pectin Degradation and Pathogenicity of Defoliating Verticillium Dahliae to Upland Cotton (Gossypium Hirsutum)
Background: Verticillium wilt (VW), caused by Verticillium dahliae Kleb., is a major plant disease that causes heavy annual losses around the world, especially in Upland cotton (Gossypium hirsutum). The disease-causing pathogen can be classified into defoliating (D) and non-defoliating (ND) pathotypes based on the induced symptoms. At present, little is known about the complex mechanisms of fungal pathogenicity and cotton resistance to it. Comparative analysis of temporal transcriptome was
... nscriptome was performed on two V. dahliae strains, Vd_086 (D) and Vd_BP2 (ND), at key development stages (hyphal growth, microsclerotia production, and spore germination) to reveal the functional process on plant defoliation and death.Results: Differentially expressed gene (DEG) analysis revealed a strong correlation between cell wall protein kinase activities and the early pathogenicity of defoliating Vd_086. With weighted gene co-expression network analysis (WGCNA), six specific gene modules were correlated with the biological traits of the fungal samples. Functional enrichment with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways together with DEG analysis revealed six pectin degrading enzymes including Polygalacturonase gene 1 (PG1), Pectate lyase gene (PEL) and Pectinesterase gene 1 (PME1) expressed in the early development of Vd_086 that may be related to the robust pathogenicity of this strain during the early invasion. The expression of four of these genes was verified by real-time quantitative reverse transcription PCR (qRT-PCR). In addition, we identified Mitogen-Activated Protein Kinase (MAPK) signaling "hub" genes that may regulate these pectinases.Conclusions: Enhanced expression of pectin degradation enzymes is associated with the stronger pathogenicity of Vd_086 than Vd_BP2, especially at early infection stages. The disease-causing capability is likely regulated by MAPK signaling genes. This study provides new insight into molecular mechanisms of the plant-pathogen interaction on the VW disease, facilitating more effective control measures against this pathogen, including molecular breeding for the VW-resistant cotton cultivars.