# Decapeptide Inducer Promotes the Conidiation of Phytopathogenic Magnaporthe oryzae via the Mps1 MAPK Signaling Pathway

## TL;DR

A decapeptide compound was found to promote spore production in the rice blast fungus by activating a specific signaling pathway.

## Contribution

Identification of a decapeptide inducer that enhances conidiation in M. oryzae via the Mps1 MAPK pathway.

## Key findings

- MCIDP significantly promotes conidiation in M. oryzae and other ascomycetes.
- MCIDP activates the Mps1 MAPK signaling pathway by upregulating key genes like WSC2, WSC3, and PKC1.
- MCIDP's effect is dependent on the Mps1 MAPK pathway, as it fails to work in related gene mutants.

## Abstract

Magnaporthe oryzae (M. oryzae) is a phytopathogenic fungus that inflicts damage on vital crops, particularly rice. Its asexual reproduction leads to the generation of numerous conidia, which is a critical factor contributing to the prevalence of rice blast disease. However, the molecules regulating the asexual reproduction of M. oryzae are unknown. In our study, to identify the molecules capable of regulating the asexual reproduction of M. oryzae, compositions of the complete medium (CM) were screened. Results showed that acid-hydrolyzed casein (AHC) could remarkably promote conidial production. One M. oryzae conidiation inducer was isolated from AHC using high-performance liquid chromatography (HPLC) under the guidance of bioassay. Its structure was further elucidated as a decapeptide compound (pyroGlu-EQNQEQPIR) by LC-MS/MS, chemical synthesis, and conidium-inducing assays, named M. oryzae conidiation inducer decapeptide (MCIDP). MCIDP could significantly promote the conidiation of M. oryzae and two other filamentous ascomycetes (Botrytis cinerea and Fusarium graminearum). The Mps1 MAPK cascade signaling pathway is crucial for conidiation, and the effect of MCIDP on this pathway was investigated to elucidate the mechanism underlying conidiation enhancement. qRT-PCR analysis demonstrated that MCIDP could remarkably upregulate the gene expression within the Mps1 MAPK cascade signaling pathway, especially the WSC2, WSC3, PKC1, MKK1, MPS1, and MIG1. Furthermore, the ΔMowsc1, ΔMowsc2, ΔMowsc3, and ΔMomid2 mutant strains were constructed. Bioassay results showed that MCIDP failed to promote conidial formation and hyphal growth in these mutant strains. These findings indicate that MCIDP promotes conidiation of M. oryzae by modulating the Mps1 MAPK signaling pathway.