SUMMARYThe genusTrichodermacontains fungi with high relevance for humans, with applications in enzyme production for plant cell wall degradation and use in biocontrol. Here, we provide a broad, comprehensive overview of the genomic content of these species for “hot topic” research aspects, including CAZymes, transport, transcription factors, and development, along with a detailed analysis and annotation of less-studied topics, such as signal transduction, genome integrity, chromatin, photobiology, or lipid, sulfur, and nitrogen metabolism inT. reesei,T. atroviride, andT. virens, and we open up new perspectives to those topics discussed previously. In total, we covered more than 2,000 of the predicted 9,000 to 11,000 genes of eachTrichodermaspecies discussed, which is >20% of the respective gene content. Additionally, we considered available transcriptome data for the annotated genes. Highlights of our analyses include overall carbohydrate cleavage preferences due to the different genomic contents and regulation of the respective genes. We found light regulation of many sulfur metabolic genes. Additionally, a new Golgi 1,2-mannosidase likely involved inN-linked glycosylation was detected, as were indications for the ability ofTrichodermaspp. to generate hybrid galactose-containingN-linked glycans. The genomic inventory of effector proteins revealed numerous compounds unique toTrichoderma, and these warrant further investigation. We found interesting expansions in theTrichodermagenus in several signaling pathways, such as G-protein-coupled receptors, RAS GTPases, and casein kinases. A particularly interesting feature absolutely unique toT. atrovirideis the duplication of the alternative sulfur amino acid synthesis pathway.

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The interactions of crops with root-colonizing endophytic microorganisms are highly relevant to agriculture, as endophytes can modify plant resistance to pests and increase crop yields. We investigated the interactions between the host plant Zea mays and the endophytic fungus Trichoderma virens at five days post-inoculation grown in a hydroponic system. Wild type T. virens and two knockout mutants, with deletion of the genes tv2og1 or vir4 involved in specialized metabolism, were analyzed. Root colonization by the fungal mutants was lower than that by the wild type. All fungal genotypes suppressed root biomass. Metabolic fingerprinting of roots, mycelia, and fungal culture supernatants was performed using UHPLC-QTOF-MS/MS. The metabolic composition of T. virens-colonized roots differed profoundly from that of non-colonized roots, with the effects depending on the fungal genotype. In particular, the concentrations of several metabolites derived from the shikimic acid pathway, including an amino acid and several flavonoids, were modulated. The expression levels of some genes coding for enzymes involved in these pathways were affected if roots were colonized by the ∆vir4 genotype of T. virens. Furthermore, mycelia and fungal culture supernatants of the different T. virens genotypes showed distinct metabolomes. Our study highlights that colonization by endophytic T. virens leads to far-reaching metabolic changes, partly related to two fungal genes. Both metabolites produced by the fungus and plant metabolites modulated by the interaction probably contribute to these metabolic patterns. The metabolic changes in plant tissues may be interlinked with systemic endophyte effects often observed in later plant developmental stages.

This chapter describes the ability of Trichoderma spp. to induce plant growth by direct and indirect mechanisms. Direct mechanisms include the facilitation or increment of nutrients uptake such as phosphate solubilization, iron sequestration and production of secondary metabolites, including phytohormones and volatile or nonvolatile compounds. Indirect mechanisms include biological control activity against plant pathogens (bacteria, fungi and nematodes) and the ability to impart abiotic stress tolerance within the plant. The 'omics' (transcriptomics and proteomics) of Trichoderma are discussed, to understand the complexity of biological processes that drive Trichoderma-plant interactions and plant growth promotion.

The sugarcane-infecting streak viruses (SISVs) are a diverse collection of mastreviruses (family Geminiviridae) within the African streak virus group. Four SISVs have currently been described, including the well-characterized maize streak virus. Here, we present a full annotated sequence record of an isolate of a new SISV species, Saccharum streak virus (SacSV), isolated in South Africa. The isolate shares less than 66% identity with any other mastrevirus, but is most closely related to Urochloa streak virus (USV), a mastrevirus from Nigeria that has until now been an outlier in the African streak virus phylogenetic tree. As with USV, the SacSV isolate we have characterized bears no obvious evidence of inter-species recombination.