MaGti1, a Gti1/Pac2 family protein, contributes to conidiation pattern shift in Metarhizium acridum

Microcycle conidiation (MC) holds substantial promise for improving both the yield and quality of conidia from entomopathogenic fungi, which are well-recognized biocontrol agents. Understanding the regulatory mechanisms governing shifts between two distinct conidiation patterns, normal conidiation (NC) and MC, is therefore critical for optimizing fungal efficacy.

In the model fungus Metarhizium acridum, MaGti1 was identified as a conserved, nuclear-localized transcription factor of the Gti1/Pac2 family. The MaGti1-disruption strain (ΔMaGti1) displayed significantly accelerated conidial germination, reducing GT₅₀ from 8.7 ± 0.03 h in the wild type to 7.5 ± 0.02 h. The ΔMaGti1 strain also exhibited enhanced tolerance to heat and oxidative stress, but showed increased sensitivity to ultraviolet-B radiation and a marked reduction in virulence. Interestingly, loss of MaGti1 caused a developmental shift from MC to NC on the microcycle medium (SYA). A domain-deletion mutant, MaGti1^ΔGPD, phenocopied ΔMaGti1, confirming that the Gti1/Pac2 domain is indispensable for MaGti1 function. Transcriptomic analysis during MC revealed 228 differentially expressed genes (DEGs) regulated by MaGti1. Among these, 13 DEGs are involved in hyphal growth, conidiation pattern regulation, and cell wall remodeling. These findings indicated that MaGti1 controls conidiation pattern shift by modulating genes linked to cell division and morphogenesis.

MaGti1 is a pivotal regulator of conidiation pattern, stress tolerance, and virulence in M. acridum, with its function dependent on the conserved Gti1/Pac2 domain. These findings provide new insights into the role of Gti1/Pac2 proteins in entomopathogenic fungi and offer a mechanistic basis for future genetic improvement of these biocontrol agents. © 2026 Society of Chemical Industry.