Lloyd J R, Landschütze V, Kossmann J
Max Plank Institut für molekulare Pflanzenphysiologie, Karl-Liebknecht Strasse 25, 14476 Golm, Germany.
Biochem J. 1999 Mar 1;338 ( Pt 2)(Pt 2):515-21.
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.
一种嵌合反义构建体被用于同时降低马铃薯块茎中两种主要淀粉合成酶同工型的活性。在所得的转基因植物中发现了一系列总淀粉合成酶活性的降低，最高可达90%的抑制率。淀粉合成酶活性的降低对淀粉颗粒产生了深远影响，与对照品系相比，其外观变得极度扭曲。对淀粉的分析表明，块茎中产生的淀粉量以及淀粉的直链淀粉含量不受活性降低的影响。为了理解淀粉颗粒为何扭曲，分离了支链淀粉并分析了其组成链长。这表明支链淀粉与对照品系的支链淀粉有很大不同。它含有更多长度少于15个葡萄糖单位的链，而长度在15至80个葡萄糖单位之间的链较少。此外，支链淀粉含有更多的超长链。我们还分析了仅抑制两种淀粉合成酶同工型之一活性的植物中的支链淀粉，此前我们已对此进行过报道。使用与之前不同的技术，我们表明两种同工型也会影响支链淀粉，但方式与两种同工型同时被抑制时不同。
