Abstract
As a C2H2 type zinc finger transcription factor, CreA is the key in Carbon Catabolism Repression (CCR) pathway, which negatively regulates the genes in carbon sources utilization. As conidiation in filamentous fungi is affected by nutritional conditions, CreA may contribute to fungal conidiation, which has been well studied in filamentous fungi, especially Aspergillus spp., but researches on entomopathogenic fungi are not enough. In this study, we found a homologous gene MaCreA in Metarhizium acridum, and the MaCreA deletion strain showed delayed conidiation, significant decrease in conidial yield, and 96.88% lower conidial production, when compared with the wild-type strain, and the normal conidiation and microcycle conidiation pattern shift was blocked. RT-qPCR showed that the transcription levels of the genes FlbD and LaeA (related to asexual development) were significantly altered, and those of most of the conidiation-related genes were higher in ΔMaCreA strain. The results of RNA-Seq revealed that MaCreA regulated the two conidiation patterns by mediating genes related to cell cycle, cell division, cell wall, and cell polarity. In conclusion, CreA, as a core regulatory gene in conidiation, provides new insight into the mechanism of conidiation in entomopathogenic fungi.
Highlights
Conidia, as the asexual propagules in many filamentous fungi, are start and end of fungal lifecycle (Adams et al, 1998; Papagianni, 2004)
We identified a homologous gene CreA in M. acridum, MaCreA, which was found to be a C2H2-type zinc finger transcription factor playing an important role in carbon catabolism repression (CCR) pathway in microorganisms (Dowzer and Kelly, 1991; Mathieu and Felenbok, 1994; Adnan et al, 2017)
Conidia are produced at the top or sides of the hyphae, whereas in microcycle conidiation, conidia are directly generated from the germ tubes or conidial cells
Summary
As the asexual propagules in many filamentous fungi, are start and end of fungal lifecycle (Adams et al, 1998; Papagianni, 2004). They are the infective form of entomopathogenic fungi, essential for their pathogenicity (Schrank and Vainstein, 2010). Asexual conidia are produced at the top or sides of the hyphae in a subsequent budding-like process for proper vegetative growth, whereas microcycle conidiation occurs when fungi are subjected to unfavorable environmental conditions. When mycelium grow to a certain extent, under the condition of external stimuli, the hyphae starts to transform into aerial mycelium, and thick-walled foot cells are formed at the tip or side of the aerial mycelium.
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