Abstract
Highly conserved, the Snf1/AMPK is a central regulator of carbon metabolism and energy production in the eukaryotes. However, its function in filamentous fungi has not been well established. In this study, we reported functional characterization of Snf1/AMPK in the growth, development and secondary metabolism in the filamentous fungus Pestalotiopsis microspora. By deletion of the yeast SNF1 homolog, we found that it regulated the utilization of carbon sources, e.g., sucrose, demonstrating a conserved function of this kinase in filamentous fungus. Importantly, several novel functions of SNF1 were unraveled. For instance, the deletion strain displayed remarkable retardation in vegetative growth and pigmentation and produced a diminished number of conidia, even in the presence of the primary carbon source glucose. Deletion of the gene caused damages in the cell wall as shown by its hypersensitivities to Calcofluor white and Congo red, suggesting a critical role of Snf1 in maintaining cell wall integrity. Furthermore, the mutant strain Δsnf1 was hypersensitive to stress, e.g., osmotic pressure (1 M sorbitol), drug G418 and heat shock, though the mechanism remains to be illustrated. Significantly, disruption of the gene altered the production of secondary metabolites. By high-performance liquid chromatography (HPLC) profiling, we found that Δsnf1 barely produced secondary metabolites, e.g., the known product pestalotiollide B. This study suggests that Snf1 is a key regulator in filamentous fungus Pestalotiopsis microspora concerting carbon metabolism and the filamentous growth, conidiation, cell wall integrity, stress tolerance and the biosynthesis of secondary metabolites.
Highlights
Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is widely found in eukaryotic cells, which plays diverse, yet critical regulatory roles in the metabolism of nutrients such as sugar, fat and protein and concerts the response of the cell to environmental stress [1,2]
As a part of our efforts to the understanding of the regulation of secondary metabolism in Pestalotiopsis microspora, we identified a homolog of snf1 in the genome of P. microspora NK17
Structural analysis of Snf1 suggested that this protein contains a catalytic kinase domain (KD) and a C-terminal domain (CTD)
Summary
Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is widely found in eukaryotic cells, which plays diverse, yet critical regulatory roles in the metabolism of nutrients such as sugar, fat and protein and concerts the response of the cell to environmental stress [1,2]. The protein phosphatase complex (Reg1/Glc7), which responses to nutrient signals (such as high concentration of glucose) dephosphorylates SNF1 to inactivated its function [8]. Known as the gauge of energy, SNF1 is generally responsive to the in vivo ratio of adenosine triphosphate (ATP) to AMP to regulate carbon metabolism. The general function of the AMPK kinase family is largely conserved over the eukaryotic domains [16,17].
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