Proteome Analysis of Hordein-Null Barley Lines Reveals Storage Protein Synthesis and Compensation Mechanisms

Hordeins
are the major barley seed storage proteins and are elicitors
of celiac disease. Attempts to reduce the hordein level in barley
have been made; however, the resultant pleiotropic effects are less
understood. Here, data-independent acquisition mass spectrometry was
used to measure proteome-wide abundance differences between wild-type
and single hordein-null barley lines. Using comparative quantitative
proteomics, we detected proteome-wide changes (∼59%) as a result
of the specific reduction in hordein proteins. The comparative analysis
and functional annotation revealed an increase in non-gluten storage
proteins, such as globulins and lipid transfer proteins, and proteins
rich in essential amino acids in the null lines. This study yields
an informative molecular portrait of the hordein-null lines and the
underlying mechanisms of storage protein biosynthesis. This study
indicates the extent to which protein content can be manipulated without
biological consequence, and we envision its wide-scale application
for studying modified crops.