PlantView Supports Stripe Rust Resistance Research: Tubby-like protein TaTLP5 enhances stripe rust resistance in wheat by regulating TaCAT1 protein degradation

New progress has been made in research on the mechanism of wheat resistance to stripe rust.

The research team led by Academician Zhensheng Kang and Professor Xinmei Zhang from Northwest A&F University published their findings in “New Phytologist” (IF = 8.1, CAS Q1 journal).

This study revealed a novel mechanism by which the Tubby-like protein TaTLP5 enhances wheat resistance to stripe rust by promoting the degradation of TaCAT1, providing new insights into ROS-mediated disease resistance regulation in plants.

Wheat is one of the world's most important staple crops, but its yield is frequently threatened by stripe rust disease caused by Puccinia striiformis f. sp. tritici (Pst). This fungal disease spreads rapidly and evolves quickly, posing a major challenge to global food security. During pathogen attack, plants rapidly produce reactive oxygen species (ROS) to eliminate invading pathogens. However, excessive ROS accumulation can also damage host cells, requiring plants to tightly regulate ROS homeostasis. Catalase (CAT), a key ROS-scavenging enzyme, plays a critical role in determining disease resistance outcomes.

Through a series of experiments, this study uncovered a new mechanism by which TaTLP5 regulates wheat resistance to stripe rust. qRT-PCR analysis showed that TaTLP5 was significantly induced during incompatible interactions with Pst. Silencing TaTLP5 resulted in enhanced susceptibility, reduced H₂O₂ accumulation, and increased levels of the negative regulator TaCAT1, whereas overexpression of TaTLP5 enhanced disease resistance and promoted ROS accumulation without affecting agronomic traits.

Protein interaction assays, including yeast two-hybrid, co-immunoprecipitation, and pull-down analyses, demonstrated that TaTLP5 interacts with TaSKP1 through its F-box domain and binds TaCAT1 via its tubby domain, thereby forming an SCF complex that promotes TaCAT1 degradation through the 26S proteasome pathway. Split luciferase complementation (SLC) assays showed strong luminescence signals between TaTLP5 and TaSKP1, as well as between TaTLP5 and TaCAT1, in tobacco leaves, while no interaction was detected with TaCAT3, indicating specific target recognition. DAB staining and fluorescently labeled fungal hyphae further revealed that TaTLP5-overexpressing plants exhibited restricted fungal growth and increased ROS accumulation, whereas the opposite phenotypes were observed in TaTLP5-silenced plants.

Experiments using Plantview

In this study, the PlantView in vivo plant imaging system was used to monitor protein degradation. Co-expression of TaCAT1-LUC, TaTLP5, and TaSKP1 resulted in a significant reduction in luminescence intensity, while treatment with the proteasome inhibitor MG132 restored the signal, confirming that TaCAT1 degradation depends on the 26S proteasome pathway.

In summary, TaTLP5 recruits TaSKP1 to form an SCF complex that promotes the degradation of the negative regulator TaCAT1, leading to elevated ROS levels and enhanced resistance of wheat to stripe rust disease.

A split luciferase complementation (SLC) assay was performed in Nicotiana benthamiana leaves to verify the interactions among TaTLP5, TaSKP1, and TaCullin1. Co-expression of TaTLP2-Nluc and TaSKP1-Cluc was used as a positive control, whereas little to no luminescence was detected in the negative controls (TaTLP5-Nluc + GUS-Cluc and GUS-Nluc + TaSKP1-Cluc).

DOI: 10.1111/nph.70956