Comparative proteome analysis of A- and B-type starch granule-associated proteins in bread wheat (Triticum aestivum L.) and Aegilops crassa.

Starch is the main component in the wheat endosperm and exists in two forms including A- and B-type granules. A bread wheat line CB037A and an Aegilops line Aegilops crassa were studied for the underlying starch biosynthesis mechanism in relation to granule types. The wheat line contains both types of starch granules while the Aegilops line only has the A-type. Differential starch granule development patterns of these two species were observed at the morphological level. A total of 190 differentially expressed proteins (DEPs) were detected between the two lines based on 2-D electrophoresis, among which 119 DEPs were identified, representing 13 unique proteins. Gene ontology annotation analysis indicated that both molecular functions and biological processes of the identified proteins are highly conserved. Different phosphorylation modification levels between the A- and B-type starch granules were found. Real-time quantitative reverse transcription PCR analysis revealed that a number of key genes including starch synthase I-1, pullulanase, isoamylase and starch branching enzyme IIa were differentially expressed between the two species. Our results demonstrated that the large granule size is associated with higher activities of multiple starch biosynthesis enzymes. The phosphorylation of starch biosynthesis enzymes is related with the formation of B-type starch granules. BIOLOGICAL SIGNIFICANCE: Analyzed the proteome, transcriptome and phosphorylation of core starch granule biosynthesis enzymes and provided new insights into the differential mechanisms underlying the A- and B-type starch granule biosyntheses.