Reproduction without sex: conidiation in the filamentous fungus Trichoderma

Abstract

2Lincoln Ventures Limited, PO Box 133, Lincoln University, Lincoln 7647, New Zealand Trichoderma spp. have served as models for asexual reproduction in filamentous fungi for over 50 years. Physical stimuli, such as light exposure and mechanical injury to the mycelium, trigger conidiation; however, conidiogenesis itself is a holistic response determined by the cell's metabolic state, as influenced by the environment and endogenous biological rhythms. Key environmental parameters are the carbon and nitrogen status and the C : N ratio, the ambient pH and the level of calcium ions. Recent advances in our understanding of the molecular biology of this fungus have revealed a conserved mechanism of environmental perception through the White Collar orthologues BLR-1 and BLR-2. Also implicated in the molecular regulation are the PacC pathways and the conidial regulator VELVET. Signal transduction cascades which link environmental signals to physiological outputs have also been revealed.

Trichoderma: sensing the environment for survival and dispersal

“…Thus, it was proposed that photoinduction is 'remembered' while a culture is maintained in conditions that do not allow cellular growth; as soon as growth is resumed, under optimal conditions, the colony conidiates (Gressel et al, 1975;Horwitz et al, 1990). Recently, Steyaert et al (2010a) interpreted these observations as showing that oxidative processes are required for completion of the developmental programme, since there appears to be a clear differentiation between the initial photoreactions and the development of conidiation.…”

“…In particular, in Trichoderma, it has been shown that conidiation is regulated by light and mycelial injury (Horwitz et al, 1985;Casas-Flores et al, 2004;Steyaert et al, 2010a). Other factors that influence conidiation include C : N status, low pH, extracellular calcium, and fungal-derived volatile organic compounds (VOCs) (Nemcovic et al, 2008;Šimkovič et al, 2008;Steyaert et al, 2010a) (Fig.…”

“…Other factors that influence conidiation include C : N status, low pH, extracellular calcium, and fungal-derived volatile organic compounds (VOCs) (Nemcovic et al, 2008;Šimkovič et al, 2008;Steyaert et al, 2010a) (Fig. 2).…”

Mycelia Growth and Spore Yield of Trichoderma harzianum in Batch and Fed-Batch Cultures: Influence of pH and Temperature

“…The growth and conidiation of Trichoderma is influenced by some known environmental factors include the ambient pH of the medium, temperature extracellular calcium, physical injury to the mycelium and the presence of fungal-derived volatile organic compounds (Steyaert et al, 2010a). In our study, two fermentation techniques; batch and fed-batch culture, and different pH and temperature conditions affected the mycelial growth and conidiation of T. harzianum.…”

“…1 mL spore suspension of T. harzianum was inoculated into Erlenmeyer flask (250 mL) containing 50 mL of liquid medium and incubated at 30 0 C for both batch and fed-batch cultures. The setup was replicated thrice after which the mycelial dry weight and spore yield was recorded after 7 days of incubation (Steyaert et al, 2010a).…”