Sex pheromone receptor Ste2 orchestrates chemotropic growth towards pine root extracts in the pitch canker pathogen Fusarium circinatum

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Authors

Ramaswe, J.B.
Steenkamp, Emma Theodora
De Vos, Lieschen
Fru, Felix Fon
Adegeye, O.O.
Wingfield, Brenda D.

Journal Title

Journal ISSN

Volume Title

Publisher

MDPI

Abstract

In ascomycetous fungi, sexual mate recognition requires interaction of the Ste2 receptor protein produced by one partner with the α-factor peptide pheromone produced by the other partner. In some fungi, Ste2 is further needed for chemotropism towards plant roots to allow for subsequent infection and colonization. Here, we investigated whether this is also true for the pine pitch canker fungus, Fusarium circinatum, which is a devastating pathogen of pine globally. Ste2 knockout mutants were generated for two opposite mating-type isolates, after which all strains were subjected to chemotropism assays involving exudates from pine seedling roots and synthetic α-factor pheromone, as well as a range of other compounds for comparison. Our data show that Ste2 is not required for chemotropism towards any of these other compounds, but, in both wild-type strains, Ste2 deletion resulted in the loss of chemotropism towards pine root exudate. Also, irrespective of mating type, both wild-type strains displayed positive chemotropism towards α-factor pheromone, which was substantially reduced in the deletion mutants and not the complementation mutants. Taken together, these findings suggest that Ste2 likely has a key role during the infection of pine roots in production nurseries. Our study also provides a strong foundation for exploring the role of self-produced and mate-produced α-factor pheromone in the growth and overall biology of the pitch canker pathogen.

Description

DATA AVAILABILITY STATEMENT: The original contributions presented in the study are included in the article/Supplementary Materials, further inquiries can be directed to the corresponding author/s.
This article belongs to the special issue titled 'Fungal Pathogens of Crops'.
SUPPORTING INFORMATION: FIGURE S1: Split marker methodology used for the disruption of the ste2 pheromone receptor gene in the wild-type genome of F. circinatum. FIGURE S2: Overview of the chemotropic assay used in this study. FIGURE S3: Chemotropic index values obtained for F. circinatum strains in the presence of untreated horse radish peroxidase (HRP) and when the enzyme was inactivated using L-ascorbate (HRP+Asc). TABLE S1: Primers used in this study. TABLE S2: PCR annealing temperatures for PCRs with the respective primer pairs used.

Keywords

Chemotropism, Split-marker constructs, G protein-coupled receptors (GPCRs), Peptide pheromone, Heterothallism, Autocrine signaling, Paracrine signaling, SDG-02: Zero hunger, SDG-15: Life on land

Sustainable Development Goals

SDG-02:Zero Hunger
SDG-15:Life on land

Citation

Ramaswe, J.B.; Steenkamp, E.T.; De Vos, L.; Fru, F.F.; Adegeye, O.O.; Wingfield, B.D. Sex Pheromone Receptor Ste2 Orchestrates Chemotropic Growth towards Pine Root Extracts in the Pitch Canker Pathogen Fusarium circinatum. Pathogens 2024, 13, 425. https://doi.org/10.3390/pathogens13050425.