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Simultaneous antisense inhibition of two starch-synthase isoforms in potato tubers leads to accumulation of grossly modified amylopectin.

ABSTRACT: A chimaeric antisense construct was used to reduce the activities of the two major starch-synthase isoforms in potato tubers simultaneously. A range of reductions in total starch-synthase activities were found in the resulting transgenic plants, up to a maximum of 90% inhibition. The reduction in starch-synthase activity had a profound effect on the starch granules, which became extremely distorted in appearance compared with the control lines. Analysis of the starch indicated that the amounts produced in the tubers, and the amylose content of the starch, were not affected by the reduction in activity. In order to understand why the starch granules were distorted, amylopectin was isolated and the constituent chain lengths analysed. This indicated that the amylopectin was very different to that of the control. It contained more chains of fewer than 15 glucose units in length, and fewer of between 15 and 80 glucose units. In addition, the amylopectin contained more very long chains. Amylopectin from plants repressed in just one of the activities of the two starch-synthase isoforms, which we have reported upon previously, were also analysed. Using a technique different to that used previously we show that both isoforms also affect the amylopectin, but in a way that is different to when both isoforms are repressed together.

SUBMITTER: Lloyd JR

PROVIDER: S-EPMC1220080 | biostudies-other | 1999 Mar

REPOSITORIES: biostudies-other

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Project description:This is a study to characterize gene expression profiles in stored Russet Burbank potato tubers. Tubers were harvested from commercial fields in the central sands region of Wisconsin in the fall of 2006. The tubers were put into storage at 55 degrees F for preconditioning and wound healing. Shortly after the temperature of the storage bin began to decrease, uniform, healthy tubers were selected for use in this microarray analysis. Tubers were at 53.6 degrees F at this time, and pieces of starch-storing tissue were collected for use as the reference sample. Other tubers were moved to temperature-controlled lockers and these were cooled gradually to either 48 or 40 degrees F following industry standard procedures. The expectation was that tubers held at 48 degrees would not have a significant accumulation of glucose and fructose, but that tubers cooled to 40 degrees would undergo low temperature sweetening and accumulate glucose and fructose to a degree that is unsuitable for processing. Three weeks later, when the locker temperatures were 48 degrees F and 41.5 degrees F, tissue samples were collected for RNA analysis. After another three weeks, samples were collected from tubers at 48 degrees F and 40 degrees F. At that time some tubers were moved from the 48 degree locker to the 40 degree locker in order to see if gene expression changes observed as a result of gradual cooling are similar to those that occur following a sudden decrease in temperature. Three weeks later, samples were collected from tubers held at 48 degrees F, tubers held at 40 degrees F, and from the tubers that were moved from 48 to 40 degrees F. At this time another set of tubers was transferred from 48 degrees to 40 degrees. Three weeks later the last samples were harvested from tubers held at 48 degrees F, from tubers held at 48 degrees F and from tubers that were transferred three weeks prior from 48 to 40 degrees. RNA was isolated from tissue extracted from three tubers. Keywords: Reference design

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Simultaneous antisense inhibition of two starch-synthase isoforms in potato tubers leads to accumulation of grossly modified amylopectin.

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