The versatility of the putative transient receptor potential ion channels in regulating the calcium signaling in Aspergillus nidulans

Abstract

ABSTRACTTransient receptor potential (TRP) channels are evolutionarily conserved integral membrane proteins. They serve as crucial mediators of sensory signals and have profound effects on cellular functions. However, many functions of the TRP family remain to be explored. In this study, the biological functions of three potential TRP channels, TrpA, TrpB, and TrpC, in Aspergillus nidulans have been verified. Green fluorescent protein labeling indicated that these TRP channels have distinct localization patterns. TrpA was primarily located at hyphal tips, TrpB showed a localization pattern resembling the Golgi apparatus, and TrpC displayed a possible ER-like localization pattern. Findings suggested that these TRP channels may be involved in different physiological processes. Deletion or reduced expression of TrpA resulted in severe growth defects and abolished conidiation. Moreover, TrpA may have multiple roles during fungal development, as TrpA mutants caused significant changes in gene expression. The lack of TrpB resulted in colony defects in a calcium-dependent manner, especially under high-temperature conditions. These defects in ΔtrpB can be largely rescued by adding calcium, indicating that TrpB is required in low-calcium conditions. The deletion of TrpC did not exhibit any detectable phenotypes under tested cultural conditions. However, when major calcium channels MidA/CchA or PmrA were absent, the lack of TrpC further exacerbated the colony defects, implying that TrpC serves as a supplementary function. In conclusion, TRP channels are involved in a wide range of physiological processes and findings provide a valuable reference for investigating the functions of TRP proteins in other fungal or eukaryotic species.IMPORTANCETransient receptor potential (TRP) ion channels are evolutionarily conserved integral membrane proteins with non-selective ion permeability, and they are widely distributed in mammals and single-cell yeast and serve as crucial mediators of sensory signals. However, the relevant information concerning TRP channels in Aspergillus nidulans remains inadequately understood. In this study, by gene deletion, green fluorescent protein tagging, and cytosolic Ca2+ transient monitoring techniques, the biological functions of three potential TRP channels (TrpA, TrpB, and TrpC) have been explored for which they play distinct and multiple roles in hyphal growth, conidiation, responsiveness to external stress, and regulation of intracellular Ca2+ homeostasis. The findings of this study on the functions of potential TRP channels in A. nidulans may serve as a valuable reference for understanding the roles of TRP homologs in industrial or medical strains of Aspergillus, as well as in other filamentous fungi.

Keywords

• transient receptor potential
• Aspergillus nidulans
• calcium channel