title: Simultaneous silencing of endo-β-1,4 xylanase genes reveals their roles in the virulence of Magnaporthe oryzae.
abstract: Due to functional redundancy, it is often difficult to genetically analyse the biological function of fungal cell wall-degrading enzymes that belong to a gene family. To overcome this difficulty, we used RNAi to knock-down (KD) multiple xylanase genes to elucidate their roles in the pathogenicity of the blast fungus, Magnaporthe oryzae. To obtain the maximum average efficiency of gene silencing for the xylanase genes, we used the 'building blocks method', in which a 40 bp sequence was chosen from an endoxylanase gene, and 10 such sequences from 10 endoxylanases were combined to make an artificial RNAi trigger by synthetic DNA. Quantitative RT-PCR analysis revealed that the transcript levels of all the expressed xylanase genes were significantly reduced in KD mutants with the artificial RNAi trigger. Even though the KD mutants did not completely lose their pathogenicity to host plants, the number of lesions, rate of penetration and extent of infected cells were all reduced in KD mutant-infected leaves. The degree of pathogenicity reduction was associated with the silencing levels of xylanase mRNA and enzymatic activity in the KD mutants. Cytological analysis indicated that xylanases play significant roles in both vertical penetration and horizontal expansion of M. oryzae in infected plants.
authors.affiliation: Laboratory of Plant Pathology, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai-cho, Nada 657-8501 Kobe, Japan.
authors.forename: Quoc Bao
authors.initials: QB
authors.lastname: Nguyen
authors.forename: Kenji
authors.initials: K
authors.lastname: Itoh
authors.forename: Ba
authors.initials: B
authors.lastname: Van Vu
authors.forename: Yukio
authors.initials: Y
authors.lastname: Tosa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nakayashiki
mesh_terms: D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D020082:Magnaporthe / Q000201:enzymology* / Q000472:pathogenicity*; D010935:Plant Diseases / Q000382:microbiology*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D037521:Virulence Factors; D043364:Endo-1,4-beta Xylanases