|Kistler, H - Corby|
Submitted to: Fungal Genetics Newsletter
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/2003
Publication Date: 3/18/2003
Citation: Chen, L., Han, Y., Suga, H., Kistler, H.C. 2003. PEP2 serves as a gratuitous pathogenicity gene in Nectria heaematococca [abstract]. Fungal Genetics Newsletter. 50:129. Interpretive Summary:
Technical Abstract: A gene cluster consisting of several genes that contribute to the pathogenicity of Nectria haematococca to pea plants is located on a fungal supernumerary chromosome. Among the cluster's pea pathogenicity (PEP) genes, PEP1, PEP2 and PEP5 as well as PDA1 (the gene for pisatin demethylase) can independently increase pathogenicity to pea when added individually to an isolate that lacks the 1.6 Mb chromosome containing the PEP cluster. PEP2 is a gene encoding a 233 amino acid protein with sequence similarity to polyadenylate binding proteins. To further examine the contribution of the PEP2 gene to fungal pathogenicity a plasmid was constructed for PEP2 gene replacement. A 13 kb BamHI / SalI fragment including PEP2 and flanking sequences was cloned in E. coli, and an internal 3.5 kb of Bgl II fragment including the entire PEP2 gene was replaced by a fungal hygromycin resistance cassette to produce the new plasmid pUCPEP2. This plasmid was used to transform wild type strain 77-13-5. Of the several transformants obtained, two (called P4 and P5) were confirmed by Southern hybridization to be gene replacements, while four transformants (P1, P6, P7 and P8) were due to ectopic integration of pUCPEP2. Another transformant (P40) was found to have lost the entire 1.6 Mb supernumerary chromosome. Tests on pea epicotyls and roots showed there was no significant difference in pathogenicity between gene replacement and ectopic transformants but that P40 was significantly lower in pathogenicity than 77-13-5. We conclude that while PEP2 can increase pathogenicity of a strain lacking the chromosome containing the PEP gene cluster, it is not essential for maximum pathogenicity in strains containing an otherwise intact 1.6 Mb chromosome. PEP2 thus may represent a gratuitous or functionally redundant pathogenicity factor in some genetic backgrounds.