Summary

A bioRxiv preprint identifies how the Pmk1, Mst12 and Bip1 network coordinates the infection process of the rice blast fungus. The network controls appressorium function, effector deployment and invasive growth.

A bioRxiv preprint describes a gene-regulatory network that helps the rice blast fungus Magnaporthe oryzae organise plant infection. The study places the Pmk1 MAP kinase and two transcription factors, Mst12 and Bip1, in a connected pathway controlling the fungus's specialised infection cell, the appressorium, as well as the deployment of proteins used during invasion.

The findings help connect a known infection signal to the extensive changes in gene activity required for the fungus to enter plant tissue. The work is presented as a preprint posted on September 14, 2026.

A signalling pathway controls the infection programme

To infect rice, M. oryzae develops an appressorium on the plant surface. This structure generates very high internal pressure, known as turgor, which allows the fungus to breach the rice leaf cuticle. Building and operating the appressorium requires coordinated changes in the activity of many genes.

The study identifies Pmk1, a mitogen-activated protein kinase, as the organising signal for this process. MAP kinases are signalling proteins that can transmit information inside a cell and alter cellular behaviour, including gene regulation. According to the preprint, Pmk1 controls a transcriptional network involving Mst12 and Bip1.

Bip1 is regulated in two ways: through Pmk1-dependent phosphorylation, a chemical modification that can change a protein's activity, and through control of its gene transcription. Mst12 also acts directly on the regulatory DNA near BIP1. The researchers found that Mst12 binds a cis-acting element upstream of BIP1 that is essential for pathogenesis. A cis-acting element is a DNA sequence that regulates the activity of a nearby gene.

Together, these results provide a molecular link between Pmk1 signalling and the activation of genes needed for infection-related development.

Mst12 and Bip1 are both necessary for regulating a group of Pmk1-dependent genes that become active during appressorium formation. The group includes genes for other transcriptional regulators, cell-wall-degrading enzymes and effector proteins.

The preprint reports that the two factors are not interchangeable. Mst12 specifically regulates functions required for appressorium-mediated penetration of the plant. Bip1 controls a distinct subset of effector genes that are deployed as the fungus invades plant tissue. Effectors are pathogen-produced molecules that can alter host-cell processes during infection.

This supports a division of labour within the network: Mst12 is particularly important for the physical penetration step, while Bip1 helps control part of the molecular toolkit used during invasion. The researchers describe the combined Pmk1–Mst12–Bip1 system as a transcriptional network required for plant infection.

The immediate importance of the work is mechanistic. Earlier research had identified regulators involved in appressorium development, but the preprint addresses how those signals can be connected to the broad transcriptional reprogramming required for infection. Mapping that connection may help researchers identify points in the fungal infection process that could eventually be investigated for disease-control strategies. The reported evidence itself concerns fungal gene regulation, appressorium function and invasive growth, rather than a tested treatment or crop-protection product.

Sources