The platelet-activating factor acetylhydrolase gene derived from Trichoderma harzianum induces maize resistance to Curvularia lunata through the jasmonic acid signaling pathway

Platelet-activating factor acetylhydrolase (PAF-AH) derived from Trichoderma harzianum was upregulated by the interaction of T. harzianum with maize roots or the foliar pathogen Curvularia lunata. PAF-AH was associated with chitinase and cellulase expressions, but especially with chitinase, because its activity in the KO40 transformant (PAF-AH disruption transformant) was lower, compared with the wild-type strain T28. The result demonstrated that the colonization of maize roots by T. harzianum induced systemic protection of leaves inoculated with C. lunata. Such protection was associated with the expression of inducible jasmonic acid pathway-related genes. Moreover, the data from liquid chromatography-mass spectrometry confirmed that the concentration of jasmonic acid in maize leaves was associated with the expression level of defense-related genes, suggesting that PAF-AH induced resistance to the foliar pathogen. Our findings showed that PAF-AH had an important function in inducing systemic resistance to maize leaf spot pathogen.     

Construction and functional analysis of Trichoderma harzianum mutants that modulate maize resistance to the pathogen Curvularia lunata

Agrobacterium tumefaciens-mediated transformation (ATMT) was used to generate an insertional mutant library of the mycelial fungus Trichoderma harzianum. From a total of 450 mutants, six mutants that showed significant influence on maize resistance to C. lunata were analyzed in detail. Maize coated with these mutants was more susceptible to C. lunata compared with those coated with a wild-type (WT) strain. Similar to other fungal ATMT libraries, all six mutants were single copy integrations, which occurred preferentially in noncoding regions (except two mutants) and were frequently accompanied by the loss of border sequences. Two mutants (T66 and T312) that were linked to resistance were characterized further. Maize seeds coated with T66 and T312 were more susceptible to C. lunata than those treated with WT. Moreover, the mutants affected the resistance of maize to C. lunata by enhancing jasmonate-responsive gene expression. T66 and T312 induced maize resistance to C. lunata infection through a jasmonic acid-dependent pathway.     

Trichoderma harzianum: a green sorbent for Pb(II) uptake from aqueous solutions

This investigation describes the use of specially cultivated, nonliving biomass of Trichoderma harzianum as a biosorbent for the batch removal of Pb(II) from a stirred system under different experimental conditions. The metal removal depended upon pH, sorbent particle size, initial Pb(II) concentration, shaking speed, and sorption time. The optimal experimental conditions for the removal of Pb(II) by T. harzianum with an initial metal concentration of 100 mg L^?1 were obtained at a particle size of 53 μm, a pH of 4.5, a shaking speed of 200 rpm, and a contact time of 720 min. The results were analyzed in terms of adsorption isotherms and kinetic models. The Freundlich isotherm model and pseudo second-order model fitted well in the data. T. harzianum proved to be a good biomaterial for accumulating Pb(II) from aqueous solutions (q = 460 mg g^?1).     

Assessment of Ni accumulation capability by fungi for a possible approach to remove metals from soils and waters

ABSTRACT

Abandoned industrial sites and mines may constitute possible hazards for surrounding environment due to the presence of toxic compounds that may contaminate soils and waters. The possibility to remove metal contaminants, specifically nickel (Ni), by means of fungi was presented exploiting a set of fungal strains isolated from a Ligurian dismissed mine. The achieved results demonstrate the high Ni(II) tolerance, up to 500 mg Ni l^?1, and removal capability of a Trichoderma harzianum strain. This latter hyperaccumulates up to 11,000 mg Ni kg^?1, suggesting its possible use in a bioremediation protocol able to provide a sustainable reclamation of broad contaminated areas.