Novel secretory protein Ss-Caf1 of the plant-pathogenic fungus Sclerotinia sclerotiorum is required for host penetration and normal sclerotial development

• Published in: Molecular plant-microbe interactions Vol. 27; no. 1; pp. 40 - 55
• Main Authors: Xiao, Xueqiong, Xie, Jiatao, Cheng, Jiasen, Li, Guoqing, Yi, Xianhong, Jiang, Daohong, Fu, Yanping
• Format: Journal Article
• Language: English
• Published: United States The American Phytopathological Society 01.01.2014
• Subjects: Amino Acid Motifs; Arabidopsis - microbiology; Arabidopsis - physiology; Ascomycota - genetics; Ascomycota - pathogenicity; Ascomycota - physiology; Ascomycota - ultrastructure; Cell Death; Daucus carota - microbiology; Daucus carota - physiology; Fruiting Bodies, Fungal; Fungal Proteins - genetics; Fungal Proteins - metabolism; Gene Library; Gene Silencing; Host-Pathogen Interactions; Models, Molecular; Mutagenesis, Insertional; Nicotiana - microbiology; Nicotiana - physiology; Nicotiana benthamiana; Oxalic Acid - metabolism; Phenotype; Phylogeny; Plant Diseases - microbiology; Plant Leaves - microbiology; Plant Leaves - physiology; Plant Roots - microbiology; Plant Roots - physiology; Sclerotinia sclerotiorum; Seedlings - microbiology; Seedlings - physiology; Stress, Physiological
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-05-13-0145-R

To decipher the mechanism of pathogenicity in Sclerotinia sclerotiorum, a pathogenicity-defective mutant, Sunf-MT6, was isolated from a T-DNA insertional library. Sunf-MT6 could not form compound appressorium and failed to induce lesions on leaves of rapeseed though it could produce more oxalic acid than the wild-type strain. However, it could enter into host tissues via wounds and cause typical necrotic lesions. Furthermore, Sunf-MT6 produced fewer but larger sclerotia than the wild-type strain Sunf-M. A gene, named Ss-caf1, was disrupted by T-DNA insertion in Sunf-MT6. Gene complementation and knockdown experiments confirmed that the disruption of Ss-caf1 was responsible for the phenotypic changes of Sunf-MT6. Ss-caf1 encodes a secretory protein with a putative Ca(2+)-binding EF-hand motif. High expression levels of Ss-caf1 were observed at an early stage of compound appressorium formation and in immature sclerotia. Expression of Ss-caf1 without signal peptides in Nicotiana benthamiana via Tobacco rattle virus-based vectors elicited cell death. These results suggest that Ss-caf1 plays an important role in compound appressorium formation and sclerotial development of S. sclerotiorum. In addition, Ss-Caf1 has the potential to interact with certain host proteins or unknown substances in host cells, resulting in subsequent host cell death.