Papers by Giovanni Vannacci
Frontiers in Plant Science, Feb 15, 2019
Molecular Plant-microbe Interactions, Sep 1, 2020
Trichoderma is a fungal genus comprising species used as biocontrol agents in crop plant protecti... more Trichoderma is a fungal genus comprising species used as biocontrol agents in crop plant protection and with high value for industry. The beneficial effects of these species are supported by the secondary metabolites they produced. Terpenoid compounds are key players in the interaction of Trichoderma spp. with the environment and with their fungal and plant hosts, however most of the terpene synthase (TS) genes involved in their biosynthesis have yet not been characterized. Here, we combined comparative genomics of TSs of 21 strains belonging to 17 Trichoderma spp., and gene expression studies on TSs using T. gamsii T6085 as a model. An overview of the diversity within the TS-gene family and the regulation of TS genes is provided. We identified 15 groups of TSs, and the presence of clade-specific enzymes revealed a variety of terpenoid chemotypes evolved to cover different ecological demands. We propose that functional differentiation of gene family members is the driver for the high number of TS genes found in the genomes of Trichoderma. Expression studies provide a picture in which different TS genes are regulated in many ways, a strong indication of different biological functions.
Plant and Soil, 2015
Background and aimsTrichoderma harzianum 6776 is a novel and beneficial tomato fungal isolate. To... more Background and aimsTrichoderma harzianum 6776 is a novel and beneficial tomato fungal isolate. To investigate the mechanisms underlying the T. harzianum 6776-tomato interaction, several physiological and biochemical responses were explored on dwarf tomato plants, cv. Micro-Tom.MethodsGrowth of treated and untreated plants was evaluated by measuring the height and biomass production of plants. The leaf pigment content and sugar partitioning in plant organs were evaluated by biochemical analysis. The photosynthetic parameters were measured by a miniaturized PAM fluorometer and a portable gas-exchange system. The hormonal analysis in root and xylem sap was performed by gas cromatography- mass spectrometry (GC-MS).ResultsT. harzianum 6776 positively affected plant growth, increasing the leaf pigment content and improving the photosynthetic activity at both stomatal and non-stomatal levels. Differences in pigment composition and photosynthetic performance were reflected in the carbohydrate content and their partitioning. In the absence of a pathogen, root and xylem vessel stress and growth-related hormone balance were affected by the interaction with T. harzianum 6776, with an increase in jasmonic and indoleacetic acids and a decrease in salicylic acid content.ConclusionsThis study shows the complex connection between increased hormone accumulation and transport, altered sugar partitioning and enhanced photosynthetic efficiency induced by T. harzianum 6776, and how growth promotion is the result of the combination of these drastic changes in Micro-Tom plants.
Fungi belonging to the genus Trichoderma are ubiquitous organisms commonly present in the soil. T... more Fungi belonging to the genus Trichoderma are ubiquitous organisms commonly present in the soil. They play an important role in biological control thanks to their advantageous ecological and physiological properties: a good environmental fitness and a high antagonistic ability against soil microorganisms. The latter include the ability to exploit competitively many different nutritional sources and mycoparasitism. Trichoderma spp. produce a large array of antibiotics and degrading enzymes allowing them to inhibit or to parasitize other fungi, including plant pathogens. Recently some new features of these fungi have been described: Trichoderma isolates are able to establish a symbiotic-like association with plants by colonizing their roots, so promoting plant growth and inducing localized and systemic resistance towards several phytopathogenic fungi. In order to effectively colonize roots and to exploit dead plant material in the rhizosphere, plant cell wall degrading enzymes, such as endopolygalacturonases (endo-PG), are critical. The aim of this study was to isolate and to sequence a gene coding for endopolygalacturonase in Trichoderma. A small genic region has been identified by PCR with degenerate primers in a T. virens isolate (I10) and it has been extended on both sides by TAIL-PCR. A genomic region 2647 bp long has been cloned and its sequence has been determined. Sequence analysis by BLAST programs confirmed its endoPG nature. Alignments with all fungal endoPG genes available in databases allowed the identification of the full T. virens coding sequence, with an extra stretch on both sides: 1185 bp in 5\u2019, 84 bp in 3\u2019 flanking the coding region. Endo-PG sequences are not available in databases for species belonging to this genus, therefore this is the first full endoPG gene sequence in a Trichoderma species. The complete endo-PG sequence from T. virens can be a starting-point for a number of purposes including the study of the nature of the symbiotic relationship between Trichoderma and plants and could open new perspectives for exploiting Trichoderma as an inducer of plant resistance
Journal of Plant Pathology, 2001
Diaporthe helianthi, the causal agent of sunflower stem canker, a serious pathogen of sunflower i... more Diaporthe helianthi, the causal agent of sunflower stem canker, a serious pathogen of sunflower in Europe, is sporadically recorded in Italy. A comparison of pathogen populations from different countries can be performed in order to detect genetically different biotypes. Our approach was turned to study molecular variability in genomic coding and non coding regions among D.helianthi isolates from different geographic origen. A set of isolates from different countries have been used to evaluate genomic variability in endo-polygalacturonase (endo-PG) genic portions and IGS region of rDNA. A PCR analysis with Fusarium moniliforme endo-PG degenerated primers produced variable amplification profiles between isolates in relation to their geographic origen. French and Yugoslavian isolates (countries where the pathogen is most aggressive) showed conserved patterns, while Italian isolates showed highly variable patterns. Primers for speciation studies in filamentous ascomycetes were used for the amplification of a portion of IGS region of rDNA. Amplification products were purified and sequenced in both directions. Phylogenetic analysis separated the isolates into two main clusters: i) all isolate from France and Yugoslavia; ii) all isolates from Italy. This investigation pointed out a good correlation between data obtained by the two different molecular approaches in order to detect intraspecific genetic variability in D.helianthi
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Papers by Giovanni Vannacci