Barley leaf rust is an ongoing threat to barley yields globally, with losses of over 30% expected when a susceptible barley line is infected with a virulent strain of the fungal pathogen. The threat of virulent pathotypes continues to emerge through evolution, and the physical migration of existing virulent types to new geographic locations.
Activity-based protein profiling (ABPP) can elucidate specific molecular interactions between barley and its leaf rust pathogen. Four near-isogenic barley lines with varying resistance to P. hordei pathotype 5453P- (=560) were infected with this pathotype. Infected tissue was profiled for serine hydrolases (SHs) and papain-like cysteine proteases (PLCPs) from both the host and the pathogen using two ABPP methods – fluorescent SDS-PAGE over an 8-day course of infection; and pull-down techniques combined with mass spectrometry at 6 days post-infection.
Fluorescent ABPP SDS-PAGE gels displayed differential banding patterns across the four barley lines, for both SHs and PLCPs. Pull-down ABPP samples also gave different mass spectrometry spectra corresponding to SHs and PLCPs. This suggests that qualitatively and quantitatively different gene expression occurs in each of the barley lines during infection with the pathotype of interest.
Linking these differential proteases with transcriptomic data over the course of infection should draw further conclusions on the specific genes expressed by the different lines under infection by P. hordei pathotype 5453P- (=560). This would allow understanding of the underlying mechanisms of resistance or vulnerability to certain pathotypes, which could inform the treatment and control of barley leaf rust, including in breeding programs.