Starch phosphorylation plays an important role in starch biosynthesis.

Starch phosphate esters are crucial in starch metabolism and render valuable functionality to starches for various industrial applications. A potato glucan, water dikinase (GWD1) was introduced in tubers of two different potato genetic backgrounds: an amylose-containing line Kardal and the amylose-free mutant amf. In both backgrounds, this resulted in two contrasting effects, a number of plants showed higher phosphate content compared to the respective control, while others lines exhibited lower phosphate content, thereby generating two series of starches with broad-scale variation in phosphate content. The results of systematic analyses on these two series of starches revealed that starch phosphate content strongly influenced starch granule morphology, amylose content, starch fine structure, gelatinization characteristics and freeze-thaw stability of starch gels. Further analyses on the expression level of genes involved in starch metabolism suggested that starch phosphorylation regulates starch synthesis by controlling the carbon flux into starch while simultaneously modulating starch-synthesizing genes.