Transcriptome analysis reveals differentially expressed storage protein transcripts in seeds of Aegilops and wheat

Abstract Transcriptional profiles of developing grain of wheat and three Aegilops species ( Ae. caudata , Ae. cylindrica , Ae. tauschii ) were compared using an EST-based array procedure. This identified 22 genes which were over-expressed in all three Aegilops species, two of which were ‘weakly similar’ to avenin storage proteins of oats. Sequencing of the corresponding transcripts demonstrated that each corresponded to a small family of proteins called avenin-like a and b. Sequence comparisons demonstrated that these proteins belong to the ‘prolamin superfamily’ of plant proteins, with the closest relatives being the γ-gliadins and LMW subunits of wheat and avenins of oats. Furthermore, the type a and b proteins differ from each other in that the latter contain a duplicated sequence of about 120 residues. The a-type proteins clearly correspond to the LMW gliadins characterised previously. In contrast, proteins corresponding to the b-type sequences have not been previously characterized but may form part of the glutenin fraction and hence contribute to processing quality. The higher expression levels of the avenin-like proteins in Aegilops species and variation in the amino acid sequences of the b-type proteins between the species suggest that they could provide a source of variation for wheat improvement.