Regulation of nitrogen availability results in changes in grain protein content and grain storage subproteomes in barley (Hordeum vulgare L.)

Barley grain protein content (GPC) is an important quality factor that determines grain end-use value. The synthesis and accumulation of grain protein is highly dependent on the availability of nitrogen fertilizer, and it is important to understand the underlying control mechanisms of this. In the current study, the GPC and protein composition of mature grain seeds from Yangsimai 3 and Naso Nijo barley cultivars were analyzed. Grain storage subproteomes (albumin, glubulin, hordein and glutelin) were compared in the cultivars grown in both low and high nitrogen level conditions. The GPC of mature grain was significantly higher in Yangsimai 3 than Naso Nijo following nitrogen treatment. Albumin, hordein and glutelin content were increased in Yangsimai, while only hordein content was increased in Naso Nijo. Large-scale analysis of the grain storage subproteome revealed 152 differentially expressed protein spots on 2-DE gels with a pH range of 3–10. Among these, 42 and 66 protein spots were successfully identified by tandem mass spectrometry in Yangsimai 3 and Naso Nijo grown in low and high nitrogen conditions. The identified proteins were further grouped into thirteen categories according to their biological functions. This detailed analysis of grain subproteomes provides information on how barley GPC may be controlled by nitrogen supply.