A potato (Solanum tuberosum) cDNA encoding an isoform of disproportionating enzyme (stDPE2) was identified in a functional screen in Escherichia coli. The stDPE2 protein was demonstrated to be present in chloroplasts and to accumulate at times of active starch degradation in potato leaves and tubers. Transgenic potato plants were made in which its presence was almost completely eliminated. It c...

Potato (Solanum tuberosum cv. Posmo) was transformed with a fungal endo-a-1,5-L-arabinanase gene (E.C. 3.2.1.99) and the enzyme secreted to the apoplast. Using promoters that are known to be sucrose inducible in potato—the granule bound starch synthase promoter and the promoter of the patatin storage protein gene—strong expression of the arabinanase was observed in developing sinks, notably the...

The major source of carbon for starch synthesis in reserve tissues such as the potato (Solanum tuberosum L.) tuber is SUC. In the developing tuber, Suc is hydrolyzed principally by Suc synthase (EC 2.4.1.13) to UDP-Glc and Fru (Preiss, 1982). Fructokinase (EC 2.7.1.4) is believed to catalyze the phosphorylation of the Fru released to yield Fru-6-P. This sugar phosphate can then be used to suppo...

Post-translational regulation plays an important role in cellular metabolism. Earlier studies showed that the activity of plastidial starch phosphorylase (Pho1) may be regulated by proteolytic modification. During the purification of Pho1 from sweet potato roots, we observed an unknown high molecular weight complex (HX) showing Pho1 activity. The two-dimensional gel electrophoresis, mass spectr...

Starch the main storage carbohydrate in higher plants Ta& 1. Characterjstjcs of the SBE c-NA from p a t o and is composed of the two polysaccharides, amylopectin (approximately 75%) and amylose (approximately 25%). Amylopectin is a highly branched a-1,4 glucan containing a1,6 branch points, whereas amylose is composed of long, linear a-1,4 glucans, some of which have very few a-1,6 branch point...

The effect of dietary fibre and starch content on digestibility, microfaunal population and caecal function was investigated in a subterranean mole-rat, Heterocephalus glaber (Rodentia). Mole-rats were fed on a diet of either sweet potato (neutral-detergent fibre (NDF) 65 g/kg dry matter (DM), starch 638 g/kg DM) or carrot (NDF 157 g/kg DM, starch 258.7 g/kg DM) for 4 weeks. Daily intake and fa...

There is no direct evidence of the effect of lignin metabolism on early storage root development in sweet potato. In this study, we found that heterologous expression of the maize leaf color (Lc) gene in sweet potato increased anthocyanin pigment accumulation in the whole plant and resulted in reduced size with an increased length/width ratio, low yield and less starch content in the early stor...

1. *Zeng, M., et al., Sources of variation for starch gelatinization, pasting and gelation properties in wheat. Cereal Chemistry, 1997. 74(1): p. 63-71. 2. *Zeleznak, K.J. and R.C. Hoseney, The role of water in the retrogradation of wheat starch gels and bread crumb. Cereal Chemistry, 1986. 63(5): p. 407-411. 3. Zeleznak K.J. and H. R.C., The glass transition in starch. Cereal Chemistry, 1987. ...

ADP-glucose pyrophosphorylase (AGPase) is a key regulatory enzyme in starch biosynthesis in higher plants. A 3.2-kb promoter of the large subunit gene of the AGPase from potato has been isolated and its activity analyzed in transgenic potato and tobacco plants using a promoter-beta-glucuronidase fusion system. The promoter was active in various starch-containing cells, including guard cells, tu...

It is well known from light microscope studies of potato starch that the granules formed in a constant environment (of light and temperature) have a ring formation indistinguishable from that of granules formed under field conditions. Electron microscope studies have confirmed that normal potato starch granules have a fine shell structure not usually resolved by the light microscope, and also t...