Combating fungal phytopathogens with human salivary antimicrobial peptide histatin 5 through a multi-target mechanism

Blast disease caused by Magnaporthe oryzae is a major contributor to decreased crop yield and rice production globally. The use of chemical fungicides to combat crop pathogens is not only unsafe but also promotes the emergence of pathogenic variants, leading to recurrent host infections. To address plant diseases, antimicrobial peptides have emerged as a promising alternative as they are effective, safe, and biodegradable antifungal agents. This study examines the antifungal activity and mechanism of action of the human salivary peptide histatin 5 (Hst5) on M. oryzae. Hst5 causes morphogenetic defects in the fungus, including non-uniform chitin distribution on the fungal cell wall and septa, deformed hyphal branching, and cell lysis. Importantly, a pore-forming mechanism of Hst5 in M. oryzae was ruled out. Furthermore, the interaction of Hst5 with the M. oryzae genomic DNA suggests that the peptide may also influence gene expression in the blast fungus. In addition to its effects on morphogenetic defects and cell lysis, Hst5 also inhibits conidial germination, appressorium formation, and the appearance of blast lesions on rice leaves. The elucidated multi-target antifungal mechanism of Hst5 in M. oryzae provides an environmentally friendly alternative to combating blast infections in rice by preventing fungal pathogenicity. The promising antifungal characteristics of the AMP peptide may also be explored for other crop pathogens, making it a potential biofungicide for the future.

Automated summary

Blast disease caused by Magnaporthe oryzae is a significant challenge for rice production worldwide. Chemical fungicides are unsafe and contribute to the emergence of resistant strains. Antimicrobial peptides, such as human salivary peptide histatin 5 (Hst5), offer a safe and effective alternative. This study investigated the antifungal activity of Hst5 on M. oryzae, finding that it causes morphological defects, inhibits germination and formation of blast lesions, and interacts with the fungus' genomic DNA. The multi-target antifungal mechanism of Hst5 provides an environmentally friendly option to combat blast infections in rice and could be explored for other crop pathogens as well.