Improved Cassava Starch by Antisense Inhibition of Granule-bound Starch Synthase I

Abstract

Cassava is a poor man's crop which is mainly grown as a subsistence crop in many developing countries. Its commercial use was first as animal feed (also known as tapioca), but has shifted since the late sixties to a source of native starch. The availability of native starches, which on the one hand do not require substantial chemical derivatisation and on the other hand have improved properties, would make cassava also for small farmers a potentially attractive cash crop. Since breeding is difficult in this polyploid, vegetatively propagated, crop a transgenic approach would be ideal to improve certain characteristics. We have created a cassava genotype producing amylose-free starch by genetic modification. The absence of amylose increased the clarity and stability of gels made with the transgenic starch, without requiring treatment with environment-unfriendly chemicals such as epoxides (propylene oxide, ethylene oxide) and acetic anhydride, which are normally used to improve stability. The amylose-free starch showed no changes in particle size distribution, chain length distribution or phosphorous content when compared to amylose-containing starch, but the granule melting temperature was increased by almost 2°C. Furthermore, the amylose-free cassava starch shows enhanced clarity and stability properties. These improved functionalities are desired in technical applications in paper and textile manufacturing, but also in the food industry for the production of sauces, dairy products and noodles.

Recent Biotechnological Advances in the Improvement of Cassava

“…As retrogradation is caused mainly by the amylose fraction in starch, amylose-free starches do not have to be treated with chemicals [19]. There are therefore efforts to generate amylose-free cassava through genetic engineering; for example, starch-free cassava was obtained by silencing GBSSI, the granule-bound starch synthase gene, which is required for the synthesis of amylose [20].…”

Evaluación De La Expresión De Genes Implicados en La Biosíntesis De Almidón en Diferentes Variedades De Yuca

“…Dichos puntos se encuentran cada 15 a 30 unidades de glucosa (Baguma et al, 2003;Zeeman et al, 2010). En el almidón de yuca, como en varias especies, la amilosa sólo llega a representar entre el 15 % al 25 %, mientras que la amilopectina representa entre el 70 % al 80 % (Raemakers et al, 2005;Sánchez et al, 2009). Las enzimas responsables de la biosíntesis del almidón no son muchas.…”

Cloning and Sequence Analysis of the Nucleotide-Binding Domain of an Alpha-Glucan, Water Dikinase Gene from Cassava (Manihot esculenta Crantz)

“…In cassava, the genes or cDNAs encoding the granule-bound starch synthase I and II involved in amylose synthesis (Salehuzzaman et al, 1993;Munyikwa et al, 1997), and the Starch Branching Enzymes (SBE) (Salehuzzaman et al, 1992;Baguma et al, 2003) have been characterized. Using crop bioengineering techniques, transgenic cassava plants producing amylose-free starch have been produced (Raemakers et al, 2005;Koehorst-van Putten et al, 2012). Transgenic cassava plants with enhanced starch production have also been reported (Ihemere et al, 2006).…”