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624 Part 5: Fruits, Vegetables, and Cerealsunique starch, with its high amylose, low amylopectin, and high
phosphorus levels, offers novel properties for food and industrial
applications. A further example of altered phosphate starch is
provided by research into potato plants deficient in GWD (pre-
viously known as R1, Lorberth et al. 1998, Ritte et al. 2002)).
The importance of starch phosphorylation becomes clear when
it is considered that starch phosphate monoesters increase the
clarity and viscosity of starch pastes and decrease the gela-
tinization and retrogradation rate. Interestingly, crops that pro-
duce high-amylose starches are characterized by considerably
lower yield (Jobling 2004). Additional transgenic or breeding ap-
proaches, as discussed in Section “Manipulation of Starch Yield”
will be required to minimize the yield penalty that goes along
with the manipulation of crops for altered starch structure and
functionality.
As discussed previously for starch yield, the importance of
starch degradative processes in determination of starch structural
properties is currently poorly understood. However, it represents
an interesting avenue for further research.CONCLUSIONS AND FUTURE
PERSPECTIVESIn this chapter we have reviewed the pathway organization of
starch synthesis within the potato tuber and detailed how it can
be modulated through transgenesis to result in higher starch
yield or the production of starches of modified structure. While
several successful examples exist for both types of manipula-
tion, these are yet to reach the field. It is likely that such crops,
once commercially produced, will yield both industrial and nu-
tritional benefits to society. In addition to this, other genetic and
biochemical factors may well also influence starch yield and
structure, and further research is required in this area in order to
fully optimize these parameters in crop species. In this context,
transgenic approaches complementary to conventional breeding
will allow more “fine-tuning” of starch properties.REFERENCES
Abel GJW, et al. 1996. Cloning and functional analysis of a cDNA
encoding a novel 139 kDa starch synthase from potato (Solanum
tuberosum L).Plant J10: 981–991.
Beck E, Ziegler P. 1989. Biosynthesis and degradation of starch in
higher plants.Annu Rev Plant Physiol Plant Mol Biol40: 95–117.
Boos W, Shuman H. 1998. Maltose/maltodextrin system ofEs-
cherichia coli: Transport, metabolism, and regulation.Microbiol
Mol Biol Rev62: 204–229.
Bologa KL, et al. 2003. A bypass of sucrose synthase leads to low
internal oxygen and impaired metabolic performance in growing
potato tubers.Plant Physiol132: 2058–2072.
Buleon A, et al. 1998. Starch granule structure and biosynthesis.Int
J Biol Macromol23: 85–112.
Chia T, et al. 2004. A cytosolic glycosyltransferase is required for
conversion of starch to sucrose in Arabidopsis leaves at night.
Plant J(in press).
Dennis DT, Blakeley SD. 2000. Carbohydrate metabolism. In: BB
Buchanan, et al. (eds.),Biochemistry and Molecular Biology ofPlants, American Society of Plant Physiologists, Rockville, pp.
630–675.
Duwenig E, et al. 1997. Antisense inhibition of cytosolic phos-
phorylase in potato plants (Solanum tuberosumL.) affects tuber
sprouting and flower formation with only little impact on carbo-
hydrate metabolism.Plant J12: 323–333.
Edwards A, et al. 1999. A combined reduction in the activity of
starch synthases II and III of potato has novel effects on the
starch of tubers.Plant J17: 251–261.
Entwistle G, Rees T. 1990. Lack of fructose-1,6-bisphosphatase in
a range of higher plants that store starch.Biochem J271: 467–
472.
Fernie AR, et al. 2001. Simultaneous antagonistic modulation of
enzyme activities in transgenic plants through the expression of
a chimeric transcript.Plant Physiol Biochem39: 825–830.
Fernie AR, Willmitzer L. 2001. Molecular and biochemical triggers
of potato tuber development.Plant Physiol127: 1459–1465.
Flipse E, et al. 1994. Expression of a wild type GBSS introduced
into an amylose free potato mutant byAgrobacterium tumefaciens
and the inheritance of the inserts at the microscopic level.Theo
Appl Gen88: 369–375.
Flipse E, et al. 1996. The dosage effect of the wild type GBSS allele
is linear for GBSS activity but not for amylose content: Absence
of amylose has a distinct influence on the physio-chemical prop-
erties of starch.Theo Appl Gen92: 121–127.
Frydman RB, Cardini CE. 1967. Studies on the biosynthesis of
starch.J Biol Chem242: 312–317.
Fulton DC, et al. 2002. Role of granule-bound starch synthase in
determination of amylopectin structure and starch granule mor-
phology in potato.J Biol Chem277: 10834–10841.
Geigenberger P. 2003a. Regulation of sucrose to starch conversion
in growing potato tubers.JExpBot54: 457–465.
———. 2003b. Response of plant metabolism to too little oxygen.
Curr Opin Plant Biol6: 247–256.
Geigenberger P, et al. 1998. High-temperature perturbation of starch
synthesis by decreased levels of glycerate-3-phosphate in grow-
ing potato tubers.Plant Physiol117: 1307–1316.
Geigenberger P, et al. 1999a. Contribution of adenosine 5’-
diphosphoglucose pyrophosphorylase to the control of starch
synthesis is decreased by water stress in growing potato tubers.
Planta209: 338–345.
Geigenberger P, et al. 1999b. Decreased expression of sucrose phos-
phate synthase strongly inhibits the water stress-induced synthe-
sis of sucrose in growing potato tubers.Plant J19: 119–129.
Geigenberger P, et al. 1997. Regulation of sucrose and starch
metabolism in potato tubers in response to short-term water
deficit.Planta201: 502–518.
Geigenberger P, et al. 2001. Tuber physiology and properties of
starch from tubers of transgenic potato plants with altered plas-
tidic adenylate transporter activity. Plant Physiol12: 1667–
1678.
Hatzfeld WD, Stitt M. 1990. A study of the rate of recycling of
triose phosphates in heterotrophicChenopodium rubrumcells,
potato tubers and maize endosperm.Planta180: 198–204.
Jenner HL, et al. 2001. NAD-malic enzyme and the control of
carbohydrate metabolism in potato tubers.Plant Physiol126:
1139–1149.
Jansson C, et al. 1997. Cloning, characterisation and modification
of genes encoding starch branching enzymes in barley. In: PJ