Proteomes of the barley aleurone layer: A model system for plant signalling and protein secretion.

The cereal aleurone layer is of major importance due to its nutritional properties as well as its central role in seed germination and industrial malting. Cereal seed germination involves mobilisation of storage reserves in the starchy endosperm to support seedling growth. In response to gibberellic acid produced by the embryo, the aleurone layer synthesises hydrolases that are secreted to the endosperm for the degradation of storage products. The barley aleurone layer can be separated from the other seed tissues and maintained in culture, allowing the study of the effect of added signalling molecules in an isolated system. These properties have led to its use as a model system for the study of plant signalling and germination. More recently, proteome analysis of the aleurone layer has provided new insight into this unique tissue including identification of plasma membrane proteins and targeted analysis of germination-related changes and the thioredoxin system. Here, analysis of intracellular and secreted proteomes reveals features of the aleurone layer system that makes it promising for investigations of plant protein secretion mechanisms.