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Abstract Detail


Metabolism

Baroja-Fernandez, Edurne [1], Munoz, Francisco Jose [1], Moran-Zorzano, Maria Teresa [1], Allocati, Juan Pablo [1], Etxeberria, Ed [5], Alonso-Casajus, Nora [1], Pozueta-Romero, Javier [7].

Enhancing cytosolic ADP-glucose synthesizing sucrose synthase activity in transgenic potato tubers results in increased starch content.

Starch is the main storage carbohydrate in plants, the total annual production from cereals and tubers of horticultural crops exceeding 3 billions tons per year. Its abundance as a naturally occurring compound is only surpassed by cellulose, and represents an important carbohydrate in human nutrition. The use of this polyglucan is becoming increasingly attractive in sectors other than food industry including production of paper, adhesives, biodegradable plastics and bioethanol.
It is widely accepted that starch is the end-product of a pathway wherein ADPG pyrophosphorylase is the only enzyme catalyzing the synthesis of the starch precursor molecule: the ADPglucose (ADPG). However, recent investigations in our laboratory have provided strong evidence indicating that sucrose synthase (SuSy) catalyzes the production of a sizable pool of ADPG linked to starch biosynthesis (Muñoz et al. 2005, Plant Cell Physiol. 46, 1366-1376). In this paper we show that SuSy-overexpressing tubers exhibit a large increase of both ADPG and starch levels as compared with WT tubers. By contrast, potato tubers expressing an Escherichia coli ADP-sugar pyrophosphatase (AspP) (Moreno-Bruna et al. 2001, Proc. Natl. Acad. Sci. USA 98, 8128-8132) in the cytosol displayed a starch- and ADPG-deficient phenotype. No pleiotropic changes in maximum catalytic activities of enzymes closely linked to starch and sucrose metabolism could be detected in the transgenic tubers. Our findings show that enhancement of ADPG-producing SuSy activity represents a potentially very useful strategy for increasing starch accumulation in heterotrophic organs. In addition, our results further strengthen the view that most of ADPG linked to starch biosynthesis (a) accumulates in the cytosol and (b) is produced by SuSy.


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1 - Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Ci
2 - Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Ci
3 - Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Ci
4 - Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Ci
5 - University of Florida, Citrus Research Center, 700 Experiment Station
6 - Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Ci
7 - Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Ci, Mutiloako etorbidea z/g, 31192 Mutiloabeti, Nafarroa, Spain, Mutilva Baja, Navarra, 31192, Spain

Keywords:
energy crop
starch
carbohydrate metabolism.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P19002
Abstract ID:95


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