title: Altered trichothecene biosynthesis in TRI6-silenced transformants of Fusarium culmorum influences the severity of crown and foot rot on durum wheat seedlings.
abstract: An RNA silencing construct was used to alter mycotoxin production in the plant pathogenic fungus Fusarium culmorum, the incitant of crown and foot rot on wheat. The transformation of a wild-type strain and its nitrate reductase-deficient mutant with inverted repeat transgenes (IRTs) containing sequences corresponding to the trichothecene regulatory gene TRI6 was achieved using hygromycin B resistance as a selectable marker. Southern analysis revealed a variety of integration patterns of the TRI6 IRT. One transformant underwent homologous recombination with deletion of the endogenous TRI6 gene, whereas, in another transformant, the TRI6 IRT was not integrated into the genome. The TRI6 IRT did not alter the physiological characteristics, such as spore production, pigmentation or growth rate, on solid media. In most transformants, a high TRI6 amplification signal was detected by quantitative reverse transcription-polymerase chain reaction, corresponding to a TRI6-hybridizing smear of degraded fragments by Northern analysis, whereas TRI5 expression decreased compared with the respective nontransformed strain. Four transformants showed increased TRI5 expression, which was correlated with a dramatic (up to 28-fold) augmentation of deoxynivalenol production. Pathogenicity assays on durum wheat seedlings confirmed that impairment of deoxynivalenol production in the TRI6 IRT transformants correlated with a loss of virulence, with decreased disease indices ranging from 40% to 80% in nine silenced strains, whereas the overproducing transformants displayed higher virulence compared with the wild-type.
authors: Dipartimento di Protezione delle Piante-Unità di ricerca Istituto Nazionale Biostrutture e Biosistemi, Università degli Studi di Sassari, Via E. De Nicola 9, I-07100 Sassari, Italy.
authors: Barbara
authors: B
authors: Scherm
authors: Marcella
authors: M
authors: Orrù
authors: Virgilio
authors: V
authors: Balmas
authors: Francesca
authors: F
authors: Spanu
authors: Emanuela
authors: E
authors: Azara
authors: Giovanna
authors: G
authors: Delogu
authors: Thomas M
authors: TM
authors: Hammond
authors: Nancy P
authors: NP
authors: Keller
authors: Quirico
authors: Q
authors: Migheli
mesh_terms: D015152:Blotting, Northern; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005670:Fusarium / Q000472:pathogenicity*; D015966:Gene Expression Regulation, Fungal; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014255:Trichothecenes / Q000096:biosynthesis*; D014908:Triticum / Q000378:metabolism / Q000382:microbiology*; D014774:Virulence / Q000235:genetics / Q000502:physiology
chemical_list: D005656:Fungal Proteins; D014157:Transcription Factors; D014255:Trichothecenes