Identification of effector CEP112 that promotes the infection of necrotrophic Alternaria solani

Abstract

Background Alternaria solani is a typical necrotrophic pathogen that can cause severe early blight on Solanaceae crops and cause ring disease on plant leaves. Phytopathogens produce secretory effectors that regulate the host immune response and promote pathogenic infection. Effector proteins, as specialized secretions of host-infecting pathogens, play important roles in disrupting host defense systems. At present, the role of the effector secreted by A. solani during infection remains unclear. We report the identification and characterization of AsCEP112, an effector required for A. solani virulence. Result The AsCEP112 gene was screened from the transcriptome and genome of A. solani on the basis of typical effector signatures. Fluorescence quantification and transient expression analysis showed that the expression level of AsCEP112 continued to increase during infection. The protein localized to the cell membrane of Nicotiana benthamiana and regulated senescence-related genes, resulting in the chlorosis of N. benthamiana and tomato leaves. Moreover, comparative analysis of AsCEP112 mutant obtained by homologous recombination with wild-type and revertant strains indicated that AsCEP112 gene played an active role in regulating melanin formation and penetration in the pathogen. Deletion of AsCEP112 also reduced the pathogenicity of HWC-168. Conclusion Our findings demonstrate that AsCEP112 was an important effector protein that targeted host cell membranes. AsCEP112 regulateed host senescence-related genes to control host leaf senescence and chlorosis, and contribute to pathogen virulence.

Transcriptome sequencing leads to an improved understanding of the infection mechanism of Alternaria solani in potato

“…A transcriptome analysis of the genes in potato and A. solani that exhibited interactions in the early infection stage showed that cell wall-degrading enzymes and metabolic processes may be important for early A. solani infection of potato [ 14 ]. In our previous study, we reported that the effector proteins AsCEP112, AsCEP19 and AsCEP20, and play important roles in late-stage A. solani infection of potato leaves [ 15 , 16 ]. In the current study, we inoculated potato leaves with A. solani and found that near the inoculation site, there were obvious whorl symptoms and tissue collapse within 72 h, and the disease spread rapidly between 96 and 120 h. Therefore, we focused on protein interaction in the late stage of infection, which was further investigated by genome-wide transcriptomic analyses.…”

“…After 7 days of incubation at 25 °C in the dark, the active mycelia growing on the T4 plate were removed with sterile slide, and the T4 plate was irradiated with UV light (ultraviolet lamp power of 8 W) for 10 min. Finally, the T4 plate was cultured in the dark for alternating periods of 25 °C/12 h and 20 °C/12 h for 3 days [ 15 ]. When the T4 plate was covered with black spores, 2 ml sterile distilled water was added to wash the T4 plate, and the spores were collected, centrifuged at 10,000 rpm, and then diluted with sterile water to obtain a 10 6 spores/mL suspension.…”

“…Furthermore, few reports have focused on the pathogenic effectors of A. solani in potato. In our previous study, the important effector proteins AsCEP112, AsCEP19 and AsCEP20 were identified [ 15 , 16 ]. AsCEP112 is an important effector protein that targets host cell membranes and regulates host senescence-related genes to control host leaf cell senescence and chlorosis, and contributes to pathogen virulence [ 15 ].…”

“…In our previous study, the important effector proteins AsCEP112, AsCEP19 and AsCEP20 were identified [ 15 , 16 ]. AsCEP112 is an important effector protein that targets host cell membranes and regulates host senescence-related genes to control host leaf cell senescence and chlorosis, and contributes to pathogen virulence [ 15 ]. The deletion of AsCEP19 and AsCEP20 from A. solani HWC-168 led to reduced virulence in potato leaves [ 16 ].…”

Network analyses reveal D clade ethylene response factors as major regulators of jasmonic acid-mediated resistance to early blight disease complex in tomato

“…Abolition of JA/ET pathways in the presence of PAMPs may be sufficient to derepress leaf senescence and therefore promote pathogen virulence. Previous studies have shown that an A. solani isolate of EBDC secretes a proteinaceous effector that increases virulence in tomato, and induces expression of senescence genes in Nicotiana benthamiana , primarily SEN4, SAG12 , and DHAR1 [114]. Orthologs of these genes are not DEGs.…”