The Corky Root Rot Pathogen Pyrenochaeta lycopersici Secretes a Proteinaceous Inducer of Cell Death Affecting Host Plants Differentially

Abstract

Pathogenic isolates of Pyrenochaeta lycopersici, the causal agent of corky root rot of tomato, secrete cell death in tomato 1 (CDiT1), a homodimeric protein of 35 kDa inducing cell death after infiltration into the leaf apoplast of tomato. CDiT1 was purified by fast protein liquid chromatography, characterized by mass spectrometry and cDNA cloning. Its activity was confirmed after infiltration of an affinity-purified recombinant fusion of the protein with a C-terminal polyhistidine tag. CDiT1 is highly expressed during tomato root infection compared with axenic culture, and has a putative ortholog in other pathogenic Pleosporales species producing proteinaceous toxins that contribute to virulence. Infiltration of CDiT1 into leaves of other plants susceptible to P. lycopersici revealed that the protein affects them differentially. All varieties of cultivated tomato (Solanum lycopersicum) tested were more sensitive to CDiT1 than those of currant tomato (S. pimpinellifolium). Root infection assays showed that varieties of currant tomato are also significantly less prone to intracellular colonization of their root cells by hyphae of P. lycopersici than varieties of cultivated tomato. Therefore, secretion of this novel type of inducer of cell death during penetration of the fungus inside root cells might favor infection of host species that are highly sensitive to this molecule.

De novo genome assembly of the soil-borne fungus and tomato pathogen Pyrenochaeta lycopersici

“…This allowed the subsequent isolation and characterization of a P. lycopersici endoglucanase which is strongly induced during the infection of tomato roots and whose expression is positively correlated with disease progression [ 17 ]. A secreted pathogenicity factor that induces cell death during the penetration of tomato roots has also been identified [ 21 ]. Here we report the de novo assembly of the P. lycopersici genome based on Illumina sequencing and the functional characterization of the draft sequence by integrating RNA-Seq data, followed by an in-depth analysis of the virulence mechanisms and potential pathogenicity effectors encoded by this soil-transmitted pathogen.…”