Transcriptional analysis of the conidiation pattern shift of the entomopathogenic fungus Metarhizium acridum in response to different nutrients

Abstract

BackgroundMost fungi, including entomopathogenic fungi, have two different conidiation patterns, normal and microcycle conidiation, under different culture conditions, eg, in media containing different nutrients. However, the mechanisms underlying the conidiation pattern shift are poorly understood.ResultsIn this study, Metarhizium acridum undergoing microcycle conidiation on sucrose yeast extract agar (SYA) medium shifted to normal conidiation when the medium was supplemented with sucrose, nitrate, or phosphate. By linking changes in nutrients with the conidiation pattern shift and transcriptional changes, we obtained conidiation pattern shift libraries by Solexa/Illumina deep-sequencing technology. A comparative analysis demonstrated that the expression of 137 genes was up-regulated during the shift to normal conidiation, while the expression of 436 genes was up-regulated at the microcycle conidiation stage. A comparison of subtractive libraries revealed that 83, 216, and 168 genes were related to sucrose-induced, nitrate-induced, and phosphate-induced conidiation pattern shifts, respectively. The expression of 217 genes whose expression was specific to microcycle conidiation was further analyzed by the gene expression profiling via multigene concatemers method using mRNA isolated from M. acridum grown on SYA and the four normal conidiation media. The expression of 142 genes was confirmed to be up-regulated on standard SYA medium. Of these 142 genes, 101 encode hypothetical proteins or proteins of unknown function, and only 41 genes encode proteins with putative functions. Of these 41 genes, 18 are related to cell growth, 10 are related to cell proliferation, three are related to the cell cycle, three are related to cell differentiation, two are related to cell wall synthesis, two are related to cell division, and seven have other functions. These results indicate that the conidiation pattern shift in M. acridum mainly results from changes in cell growth and proliferation.ConclusionsThe results indicate that M. acridum shifts conidiation pattern from microcycle conidiation to normal conidiation when there is increased sucrose, nitrate, or phosphate in the medium during microcycle conidiation. The regulation of conidiation patterning is a complex process involving the cell cycle and metabolism of M. acridum. This study provides essential information about the molecular mechanism of the induction of the conidiation pattern shift by single nutrients.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2971-0) contains supplementary material, which is available to authorized users.

The MaCreA Gene Regulates Normal Conidiation and Microcycle Conidiation in Metarhizium acridum

“…Recently, studies about microcycle conidiation mostly focus on the phenotypic observation in different fungi (Souza-Paccola et al, 2015; van Heerden et al, 2016; Rosli et al, 2018). In the preliminary work in our lab, we found that normal conidiation and microcycle conidiation are involved in lipid metabolism, sugar chain biosynthesis, and metabolism and translation (Wang Z. et al, 2016). Nevertheless, the mechanism of the shifts of the two conidiation patterns remains unclear.…”

“…They are the infective form of entomopathogenic fungi, essential for their pathogenicity (Schrank and Vainstein, 2010). In filamentous fungi, normal conidiation and microcycle conidiation are the two patterns of asexual conidiation (Zhang et al, 2010; Jung et al, 2014; Wang Z. et al, 2016). In normal conidiation, 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.…”

“…In M. acridum , microcycle conidiation has been reported to produce 4–5-fold higher conidia yield, with the generated conidia exhibiting increased heat resistance and trehalose level, but similar UV-B resistance and virulence, when compared with those produced by normal conidiation (Zhang et al, 2010). A recent study revealed that regulation of conidiation pattern in M. acridum is a complex process involving cell cycle and metabolism (Wang Z. et al, 2016). Nevertheless, the mechanism of microcycle conidiation remains unclear.…”

MaSln1, a Conserved Histidine Protein Kinase, Contributes to Conidiation Pattern Shift Independent of the MAPK Pathway in Metarhizium acridum

“…In normal conidiation, conidia are generated after the mycelia have properly extended, while in microcycle conidiation, new conidia can be formed directly from the germinated ones ( 8 ). Under certain, specific conditions, the two patterns are interconvertible ( 9 – 11 ). Two conidiation patterns also exist in Metarhizium acridum , a locust-specific pathogen, and microcycle conidiation exhibited great potential for improving the productivity and quality of conidia ( 12 ).…”

Transcription Factor Mavib-1 Negatively Regulates Conidiation by Affecting Utilization of Carbon and Nitrogen Source in Metarhizium acridum

“…The fungi can bypass the mycelia period in MC and develop secondary conidia from germ tubes or directly from conidial cells [ 1 , 4 , 14 ]. MC is a special survival mechanism of fungi under adverse conditions, such as high temperature [ 10 , 11 , 15 ], extreme pH [ 16 ], high salt content [ 17 ], and nutritional deficiencies [ 4 , 18 , 19 , 20 ]. Among them, nutritional deficiency is the important factor that affects the fungal growth and development.…”