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Involvement of MaSom1, a downstream transcriptional factor of cAMP/PKA pathway, in conidial yield, stress tolerances, and virulence in Metarhizium acridum

  • Applied genetics and molecular biotechnology
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Abstract

Flo8/Som1, which functions downstream from the cyclic AMP (cAMP)-dependent protein kinase A (PKA) pathway, plays important roles in hyphal development, spore formation, and virulence in yeast and several filamentous fungi. However, the functions of Som1 in entomopathogenic fungi are still a mystery. In this study, MaSom1, a Flo8/Som1 homolog, was identified and functionally characterized in a model entomopathogenic fungus Metarhizium acridum. Similar to Flo8/Som1 in other fungi, MaSom1 mainly localized to the nucleus in M. acridum. Disruption of MaSom1 reduced conidial yield, delayed conidial germination, and impaired the fungal tolerances to heat and UV-B. The expression levels of some genes involved in defenses of heat shock and UV-B radiation were significantly reduced in ΔMaSom1. MaSom1 is also important for cell wall integrity and conidial surface structures in M. acridum. Some genes related to fungal cell wall synthesis were downregulated in ΔMaSom1. Bioassays showed that ΔMaSom1 had a dramatically decreased virulence after both topical inoculation and intrahemocoel injection of the fungus in locusts. Moreover, inactivation of MaSom1 reduced appressorium formation, diminished fungal growth in locust hemolymph in vitro, and enhanced insect immune responses. Taken together, these results indicate that disruption of MaSom1 leads to a decline of fungal virulence because of impairments in conidial germination and appressorium formation, reduction of fungal growth in host hemolymph, and enhancement of insect immune responses owing to the changes in conidial surface structures.

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Funding

This work was supported by the Natural Science Foundation of China (no. 31471820), the Natural Science Foundation Project of Chongqing (CSTC 2015JCYJA80037), and the Fundamental Research Funds for the Central Universities (106112017CDJQJ298831).

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  1. Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing, 401331, People’s Republic of China

    Yanru Du, Kai Jin & Yuxian Xia

  2. Chongqing Engineering Research Center for Fungal Insecticide, Chongqing, 401331, People’s Republic of China

    Yanru Du, Kai Jin & Yuxian Xia

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  1. Yanru Du
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  2. Kai Jin
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Correspondence to Kai Jin or Yuxian Xia.

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Du, Y., Jin, K. & Xia, Y. Involvement of MaSom1, a downstream transcriptional factor of cAMP/PKA pathway, in conidial yield, stress tolerances, and virulence in Metarhizium acridum. Appl Microbiol Biotechnol 102, 5611–5623 (2018). https://doi.org/10.1007/s00253-018-9020-7

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