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Trichoderma-Plant-Pathogen Interactions: Advances in Genetics of…

- - - - :check: ion fluxes
      - :check: oxidative burst
      - :check: deposition of callose
      - :check: synthesis of polyphenols
      - salicylate (SA) & jasmonate/ethylene (JA/ET)-signalling
        
        vary degrees of tolerance to pathogen invasion
    - - resembles the response triggered by plant growth-promoting
        rhizobacteria (PGPR).
    - - a PKS/NRPS hybrid enzyme involved in defense
        responses in maize
    - - Sm1/Epl1
        
        :check: abundantly secreted
        
        :check: small cysteine-rich hydrophobin-like
        protein of the cerato-platanin (CP) family
        
        Deletion of this Trichoderma gene impairs elicitation of ISR
        
        is in a glycosylated state which is essential for elicitation properties
        
        susceptible to oxidative-driven dimerization in plants rendering Sm1 inactive as inducer of ISR
  - - - Induce transcriptomic changes in plant
      - Protect plant from diseases and abiotic stress
      - some colonize the surface of glandular trichomes and then form appressoria-like structures.
  - - - TasHyd1 from T.asperellum and Qid74 of T.harzianum
- - - - sensing of the host/prey fungus
      - attraction
      - attachment
      - coiling around
      - lysis brought about by hydrolytic enzymes
    - - 7 transmembrane G protein coupled receptor Gpr1 involved in sensing fungal prey:
        
        silencing of gpr1 gene in T. atroviride rendered the mycoparasite unable to respond to the presence of the host fungus
      - most other filamentous fungi, Trichoderma spp. have 2 MAPK cascades comprising
        
        MAPKK
        
        MAPK
        
        MAPK pathways act in mycoparasitism and biocontrol
        
        MAPKKK
      - binding of ligand to receptors leads to downstream signaling events via activation of G-protein cascades
        
        deletion of the adenylate cyclase gene tac1 severly impaired growth and mycoparasitic abilities of T. atroviride
        
        deletion of the Tga3 G-alpha affcet the mycoparasitic abilities of T. atroviride (similar way to loss of Gpr1)
  - - - attachment to and attack of host fungi by Trichoderma is accompanied by:
        
        formation of appresoria or papillae-like structures
        
        coiling around host hyphae
      - genetics underlying attachment of mycoparasite to the host are not well understood
      - lacking of experimental evidence causes:
        
        indirect support for the involvement of hydrophobins that T. virens mutants in the transcriptional regulator of secondary metabolism and morphogenesis Ve11 that have low hydrophobin expression
    - - Chitinases
        
        deletion pf chit422lech42 (not drastic).
      - Glucanases (cell-wall lytic enzymes)
        
        mycoparasitism/ bopcontrol
        
        Deletion of tvbgn3 (b-1,6-glucanase-encoding) reduced the mycoparasitic and biocontrol potential of T. virens against P. ultimum .
        
        Co-overexpression of two b-glucanases (Bgn2 and Bgn3)
        
        Increase biocontrol T. virens against R. solani,
        P. ultimum and Rhizopus oryzae
      - Prb1/Sp1
        
        induced during mycoparasitism
        
        biocontrol
      - Secondary metabolites
        
        Gliotoxin & Gliovirin
        
        Supression of R. solani and P. ultimum .
        
        Tex1 (non-ribosomal peptide synthetase)
        
        assemble 18-residue peptaibol (trichovirin II) and by using Dtex1 mutants the trichovirin II type peptaibols
        
        trigger induced resistance in plants
        
        11- and 14-modules peptaibols by a single
        NRPS (Tex2 of T. virens)
        
        peptaibiotics
        
        strongly antimicrobial ( able to
        form voltage-gated membrane channels)
        
        T. pseudokoningii peptaibol trichokonin VI
        
        induce programmed cell-death in *Fusarium
        oxysporum*
        
        T. atroviride 6-pentyl-2H-pyran-2-one
        
        role in Trichoderma–plant and
        Trichoderma–fungal interactions
        
        transcription factor,
        Thctf1, involved in the biosynthesis of 6-PP has been
        characterized