U. S. Singh

Overlapping and distinct functions of two Trichoderma virens MAP kinases in cell-wall integrity, antagonistic properties and repression of conidiation.

We have studied the functions of the Trichoderma virens TmkB, a homologue of the yeast cell-wall integrity MAP kinase Slt2, using gene knockout. The functions of TmkB were compared to those of the pathogenicity MAP kinase homologue (TmkA). Like the tmkA loss-of-function mutants, tmkB mutants exhibited reduced radial growth and constitutive conidiation in dark as well as in liquid shake cultures. The tmkB mutants, in contrast to tmkA mutants, had cell-wall integrity defects, as shown by autolysis of the mycelia and increased sensitivity to cell-wall degrading enzymes. Interestingly, the tmkB mutants were not autolytic on the synthetic Vogels minimal medium. The tmkB mutants had attenuated ability to overgrow the plant pathogen Sclerotium rolfsii, while retaining the ability to overgrow Rhizoctonia solani and Pythium spp., a phenotype also exhibited by the tmkA mutants. This first functional analysis of a cell-wall integrity MAPK in Trichoderma spp., a group of economically important fungi, shows the importance of this signaling pathway in biocontrol. Common phenotypes of the TmkA and TmkB pathways suggest that the two MAPKs may share some substrates, perhaps subunits of key transcription factors, thus dependent on two phosphorylation events for their activity.

The influence of light on the biology of Trichoderma.

During evolution, almost all forms of life on earth have been exposed to different electromagnetic radiation of internal and external origin, and are ultimately maintained by transformation of the energy contained in the electromagnetic radiation emitted by the sun. Plants capture the sun’s energy and use it to synthesize energy-rich molecules (sugars) from molecules of carbon dioxide and water. These molecules then serve, directly or indirectly, as the source of energy for plants themselves and ultimately for all animals and decomposer organisms (such as bacteria and fungi). But many organisms use sunlight in other ways. Apart from its energetic content, sunlight has properties (such as intensity, duration, polarization or spectral composition) that provide patterns, which in turn have important consequences for living organisms. In particular, these patterns have the potential to be used as a source of information by a cognitive agent or can be used to produce thermodynamic work. In their natural habitat, all forms of life are continuously obtaining and decoding information from their environment (including that contained in light), which they use for their own benefit. In this sense, the human