Wheat yellow rust, caused by Puccinia striiformis f.sp. tritici (Pst), is one of the most
destructive diseases of wheat. The Yr15 resistance gene, cloned in our lab from wild emmer wheat, encodes Wheat Tandem Kinase 1 (WTK1), a protein with tandem kinase and pseudokinase domains. According to our model, WTK1 can directly sense pathogen effectors, resulting in the activation of plant immune responses. Unlike other cloned tandem kinases, WTK1 contains unique kinase membership comprising RLK_Pelle_WAK RLK_Pelle_RLCK_VIII.
Recent large-scale analyses of the tandem kinase protein family across 104 plant genomesconfirmed that TKPs are widely distributed in the plant kingdom and often integrate pseudokinase domains or additional domains as decoys, highlighting WTK1 as one of the first functionally validated members of this emerging class of immune receptors.
To investigate the downstream processes triggered by WTK1, we employ proximity labeling coupled with mass spectrometry to capture WTK1-associated proteins. For this purpose, we generated transgenic wheat lines carrying BirA-control and WTK1-HA-BirA constructs. These materials enable biotin labeling directly in wheat, providing a powerful system to monitor proteins recruited during immune activation. Our experimental results demonstrate that transgenic WTK1-HA-BirA plants retain resistance to P. striiformis, indicating that BirA fusion does not interfere with the functionality of WTK1. In addition, our initial experiments indicated that BirA and WTK1-HA-BirA labeled distinct sets of proteins.
This approach provides a novel entry point to understand tandem kinase-mediated immunity and to develop strategies for durable rust resistance in wheat.
