The low affinity glucose transporter HxtB is also involved in glucose signalling and metabolism in Aspergillus nidulans

Abstract

One of the drawbacks during second-generation biofuel production from plant lignocellulosic biomass is the accumulation of glucose, the preferred carbon source of microorganisms, which causes the repression of hydrolytic enzyme secretion by industrially relevant filamentous fungi. Glucose sensing, subsequent transport and cellular signalling pathways have been barely elucidated in these organisms. This study therefore characterized the transcriptional response of the filamentous fungus Aspergillus nidulans to the presence of high and low glucose concentrations under continuous chemostat cultivation with the aim to identify novel factors involved in glucose sensing and signalling. Several transcription factor- and transporter-encoding genes were identified as being differentially regulated, including the previously characterized glucose and xylose transporter HxtB. HxtB was confirmed to be a low affinity glucose transporter, localizing to the plasma membrane under low- and high-glucose conditions. Furthermore, HxtB was shown to be involved in conidiation-related processes and may play a role in downstream glucose signalling. A gene predicted to encode the protein kinase PskA was also identified as being important for glucose metabolism. This study identified several proteins with predicted roles in glucose metabolic processes and provides a foundation for further investigation into the response of biotechnologically important filamentous fungi to glucose.

Enhancing peptaibols production in the biocontrol fungus Trichoderma longibrachiatum SMF2 by elimination of a putative glucose sensor

“…Particularly, the gene SMF2FGGW_104114 encoding a putative hexose transporter that shares high sequence identity (75.9%) with the high‐affinity glucose transporter Hgt‐1 in N. crassa (Wang et al, ) is significantly downregulated during both the 36‐hr and 60‐hr cultivation period. Two relatively close homologs (SMF2FGGW_104773 and SMF2FGGW_101765) of the low‐affinity glucose transporters, Glt‐1 in N. crassa and HxtB in A. nidulans (Dos Reis et al, ; Wang et al, ), also exhibit downregulated expression in the Δ Tlstp1 mutant.…”

Forward genetics screen coupled with whole-genome resequencing identifies novel gene targets for improving heterologous enzyme production in Aspergillus niger

“…That mutation of mstC results in increased expression of genes under P glaA could indicate that MstC is involved in nutrient signaling as a transceptor. Initially characterized in Saccharomyces , transceptors have amino acid similarity to—and may function as—transporters, but also act as signal-transducing receptors involved in sensing nutrient availability (Diallinas 2017 ; dos Reis et al 2017 ; Ozcan et al 1996 ). One possible explanation for the impact of ∆ mstC on P glaA -controlled proteins is that mstC encodes (or its deletion induces) a transceptor involved in signaling levels of maltose, glucose, or a combination of the two.…”

Putative Membrane Receptors Contribute to Activation and Efficient Signaling of Mitogen-Activated Protein Kinase Cascades during Adaptation of Aspergillus fumigatus to Different Stressors and Carbon Sources

“…Analyses of intracellular trehalose levels (Megazyme) and PKA activity (Promega) were carried out according to the manufacturer’s instructions. Intracellular glycogen levels and extracellular glucose concentrations were quantified as described previously ( 58 ).…”