The mycoparasite Trichoderma harzianum, a biocontrol agent, forms coils and other mycoparasitic structures upon contact with host fungi. A biomimetic system consisting of nylon fibres was used to test the involvement of signal transduction pathways in the induction of coils. Two activators of G protein-mediated signal transduction induced coiling of hyphae around nylon fibres. The peptide toxin mastoparan increased coiling more than two-fold in comparison with controls. The activator fluoroaluminate (A1F4−) had a similar effect, whereas aluminium ions alone were ineffective. cAMP increased coiling about three-fold. Although the two G protein activators, mastoparan and fluoroaluminate, have very different modes of action, they share the Gα subunit as a target. We also found that two T. harzianum isolates differ in their extent of coiling around nylon fibres in the absence of effectors. The results reported here demonstrate that the biomimetic system can be used to study the biochemistry of coil induction, and will be a valuable assay to aid in the genetic manipulation of this pathway. It is proposed that a signal for mycoparasitic behaviour from the host cell surface is transduced by heterotrimeric G protein(s) and mediated by cAMP.

Teliospore germination in Cintractia limitata and C. mitchellii is illustrated and shown to agree closely with that earlier reported in two other species of the genus. Basidial cells conjugate pairwise, and from each united pair a relatively large, and probably dikaryotic, blastoconidium is produced. In C. mitchellii, as a rare event, conjugation does not occur and cells of the basidium form small basidiospores. It is pointed out the course of teliospore germination in Cintractia spp. departs markedly from the standard Ustilago type.

Truffles live in an environment poor in oxygen, and are a good model for investigation of enzymatic adaptation to microaerobic conditions. We studied the antioxidant and glutathione dependent enzymatic endowment of Tuber truffles. Superoxide dismutase, catalase, glutathione peroxidase Se dependent, glutathione reductase, glyoxalase 1 and glyoxalase 2 are expressed and correlate with the microaerobic metabolism, growth rate and mycorrhizal symbiosis of truffles. A very low or undetectable glutathione S-transferase activity was found. For comparison the same enzyme activities were investigated in Agaricus bisporus which is epigeous and non-mycorrhizal.