Epsilon Open Archive

Abstract

Starches in various forms are an important part of the human diet. Furthermore, the use of starch as a renewable and biodegradable raw material for various industrial applications is becoming increasingly attractive. Non-food applications of starch make new demands on quality and type of starches produced. Ideally these new demands should be met by tailoring starches within the plant. A number of such in planta produced specialty starches exist today, e.g. high-amylose starch. Our aims with this Ph.D. project have been to increase the knowledge of starch synthesis and caryopsis development. We have attempted to do this primarily by investigating the proteins entrapped within the starch granule. This has been done using proteomic techniques. Our main focus has been on characterizing a barley mutant with high amylose starch, amo1. Apart from proteomic characterization of granule proteins we have also done comparative starch characterizations and assayed for starch branching activity in mutant and wild type seeds. We also investigated the occurrence of a caspase-like protease activity, a VEIDase, during caryopsis development. A protocol for extracting proteins from starch granules has been developed and a 2D proteomic reference map of integral granule proteins established. The molecular mechanism of a fragmentation of granule proteins induced during sample preparation has been found. An alternative sample preparation procedure has been established that reduces fragmentation considerably. A developmentally regulated caspase-like proteolytic activity, a VEIDase, with possible connection to developmental programmed cell death, has been characterized and found to be chiefly active during early stages of caryopsis development. The VEIDase activity has been localised to small vesicles in starchy endosperm cells.