Stripe rust fungus subverts wheat phase separation–mediated immunity to promote infection

As a major staple crop in China, wheat has an annual planting area of approximately 24 million hectares. However, wheat stripe rust, caused by the ction of the wheat-specific form of *Puccinia striiformis* (*Puccinia striiformis* f. sp. *tritici*, abbreviated as Psas long been a major fungal disease threatening the safe production of wheat in China. During the long process of co-evolution between plants and pathogens, the question of how pathogens manipulate host defense me and achieve immune evasion through secreted effector proteins remains a central scientific challenge in the field of plant pathology.

In their previous work, the research team identified and characterized a stripe rust effector protein, Hasp170, annd that this protein can infiltrate the wheat cell nucleus and effectively suppress the plant's immune response. Through validation using RNAi transgenic wheat materials, the team confirmed t Hasp170 is a key virulence factor of stripe rust, and its nuclear localization is decisive for the exertion of toxicity.To further elucidate the specific molecular mechanism by which the effe protein Hasp170 exerts its toxicity within the host cell nucleus, researchers further identified a wheat nuclear protein, TaPSTE, that interacts with Hasp170nal analysis results indicate that TaPSTE acts as a positive regulator in wheat resistance to stripe rust; when this gene is knocked out, wheat disease resistance significantly decreases, whereas overexpre of the gene significantly enhances resistance. Further research revealed that TaPSTE undergoes liquid-liquid phase separation via its intrinsically disordered region (IDR1) to assemble dyn condensates within the nucleus, and this phase separation ability is indispensable for TaPSTE to exert its resistance function.

Further research indicates that the condensates formed by TaPSTE in the nucleus recruit various transcription-related components, including the transcription fac-YC, thereby activating downstream immune signaling pathways such as Ca²⁺-CDPK-RBOH-ROS, ultimately achieving the reprogramming expression of immune-related genes. However, the effe protein Hasp170 secreted by the stripe rust fungus can directly bind to the IDR1 domain of TaPSTE, interfering with its self-interaction and the assemby of the TaPSTE-TaNF-YC phase-separated complex, thereby inhibiting the transcriptional regulatory function of this module, ultimately weakening the wheat immune response mediated by R²⁺, allowing the pathogen to successfully infect and colonize the host tissue.

This study represents the first report in the field of plant-fungal interactions demonstrating that a pathogen effector protein interferes with host liquid-liquid phas separation, revealing a new dimension of the "arms race" between pathogens and plants, and providing important theoretical support and precise molecular targets for elucidating the pathogenic mechanism uccinia striiformis* f. sp. *tritici* and breeding new disease-resistant wheat varieties.

The co-first authors of the paper are Yan Tong, a graduated student, and Zhao Jinren and Chen Can, PhD candidates, from the College of Plant Protection at Northwest A&F University. The co-corresponding authors are Professor Wangand Researcher Tang Chunlei. Additionally, Academician Kang Zhensheng, Professor Jiang Cong, and Professor Wang Ning from the College of Plant Protection at Northwest A&Fy, Professor Fang Xiaofeng from Tsinghua University, and Researcher Yang Lijun from the Hubei Academy of Agricultural Sciences provided important support for the successful complef this study.