Host-specific toxins: effectors of necrotrophic pathogenicity

Area of Science:

• Plant pathology
• Fungal genetics
• Molecular biology

Background:

• Host-specific toxins (HSTs) are critical effectors in plant diseases, targeting specific host genotypes.
• Classical HST pathogens include Cochliobolus, Alternaria, and Pyrenophora species.
• Recent research highlights Stagonospora nodorum producing multiple HSTs interacting with wheat resistance loci.

Purpose of the Study:

• To investigate the phylogenetic distribution and evolutionary mechanisms of HST genes in fungal plant pathogens.
• To explore the potential for lateral gene transfer as a conserved mechanism for HST acquisition in Pleosporales.

Main Methods:

• Phylogenetic analysis of fungal pathogens.
• Comparative genomics to identify HST genes.
• Evidence assessment for lateral gene transfer events, focusing on the ToxA gene.

Main Results:

• Stagonospora nodorum identified as producing at least four HSTs interacting with wheat.
• Pleosporales order identified as a potential hub for HST pathogens.
• Strong evidence for lateral gene transfer of the ToxA gene from S. nodorum to Pyrenophora tritici-repentis.

Conclusions:

• Pleosporales pathogens may possess a conserved tendency to acquire HST genes via lateral gene transfer.
• Lateral gene transfer is a plausible mechanism driving the evolution and spread of HSTs in fungal pathogens.
• Understanding HSTs and their acquisition is crucial for developing durable disease resistance strategies in crops.