**6. Perspectives of GMO starches**

Two starch phosphorylases in plants, plastidic phosphorylase A (Pho 1a) and cytosolic phosphorylase (Pho 2), catalyse reversible transfer of glucose from glucose-1-phosphate to a-glucan chain-releasing phosphorus (pi). A gene was cloned which translated protein counterpart was involved in starch metabolism identified by its ability to bind the potato starch granules [31]. The gene was introduced as RNAi construct in the potato using the *Agrobacterium* mediated transformation method. Biochemical analysis revealed that the reduction in the protein level of transgenic potato augmented with reduction in the phosphate content of the starch. The complementary result is obtained when the same gene was expressed in *E. coli*, as this leads to an increased phosphate content of the glycogen. It was assumed that this protein might be responsible for the incorporation of phosphate into starch-like glucans, a process that is not understood at the biochemical level. The reduced phosphate content in potato starch have some secondary effects on its degradability, as the respective plants show a starch excess phenotype in leaves and a reduction in cold-sweetening in tubers. In a mapping study in potato, Pho 1a emerged as a candidate gene linked to starch gelling and starch granule size [47]. In another study, it was found that the antisense inhibition of isoamylase in potato induces massive numbers of small granules in tubers, suggesting that the debranching activity is necessary to prevent excessive granule initiation [48]. On the other hand, it has been observed that mutation of starch synthase IV in *Arabidopsis* increases the starch granule size in leaf [28]. However, despite these observations, we really have a poor understanding of what

controls granule size and shape.

28 Potato - From Incas to All Over the World

**4. Potato starch engineering for industrial application**

The principal industrial productions of starches are based only on four main resources such as maize, cassava, wheat, and potatoes, which represent 76, 12, 7, and 4%, respectively. The other botanical resources represent less than 1%. The main production areas are North America, China, Europe, Southeast Asia, and South America with 33, 33, 18, 11, and 5%, respectively. Along with the better understanding of starch structure and enzymes involved in starch biosynthesis, many of the genes that encode these enzymes have been cloned and transformed into plants using *Agrobacterium tumefaciens* to modify the starch metabolism. Transgenic plants have been generated by down regulation (antisense or co-suppression approaches) or over-expression of endogenous gene or expression of heterologous genes, where starch properties and morphology have been altered. The possibility to produce tailor-made starches in planta has broadened the functionality of starches in industrial applications. The in planta modified starches, such as the amf starch, are often of better quality relatively to the chemically derivative which excludes the use of hazardous chemicals and leads to energy savings in the production process (of up to 60% for, e.g., synthetic polymer replacers). Potato starch shows a naturally high degree of phosphorylation compared to starches from other crops. It is universally acknowledged that starch with longer polymer chains tends to contain higher levels of phosphate because the longer chains provide a better substrate for the phosphorylating enzyme. The presence of phosphate in potato starch results in the stable-paste properties and transparent gels. Hence, potato starch is preferred for use in paste products and as an

In an era towards a bio-based economy, the knowledge on how to improve complex carbohydrates such as starch is essential. A deeper understanding of the starch biosynthetic pathway, how storage starch granules are formed and how the composition, size, and shape can be changed and optimised for different bio-products, is of great importance for food and non-food applications. Despite its great importance, the development and commercialisation of crops with altered starch properties using biotechnological approaches is being hampered by regulatory hurdles. The very high costs and the great deal of time needed, associated with the regulation of genetically modified crops (GMOs), are major problems. Although there is currently one GMO potato variety in the market, the *Amflora*, the commercialisation of this variety has been challenged by farmers and environmental organisations. The development of new methods in plant breeding that would circumvent these regulatory problems would be of greatly stimulated the development of novel starches [55]. The identification of genetic marker associated with starch properties and the exploitation of new mutations in tilling populations are other tools with great potential for uncovering key genes determining starch properties [47]. Another bottleneck to produce improved starches is associated with the difficulties in predicting beforehand the effect of a (trans) gene. The understanding of mechanism by which starch granules are made in the form of dense granules would be a great step forward in the synthesis of tailored starches for different bio-based applications.

[3] Jobling SA, Westcott RJ, Tayal A, Jeffcoat R, Schwall GP. Production of a freeze-thawstable potato starch by antisense inhibition of three starch synthase genes. Nature

Genetically Modified Potato as a Source of Novel Carbohydrates

http://dx.doi.org/10.5772/intechopen.71079

31

[4] Matheson NK. The chemical structure of amylose and amylopectin fractions of starch from tobacco leaves during development and diurnally nocturnally. Carbohydrate

[5] Hoover R. Composition, molecular structure, and physicochemical properties of tuber and root starches: A review. Carbohydrate Polymer. 2001;**45**:253-267. DOI: 10.1016/

[6] Blennow A, Bay-Smidt AM, Leonhardt P, Bandsholm O, Madsen HM. Starch paste stickiness is a relevant native starch selection criterion for wet-end paper manufacturing.

[7] Wiesenborn DP, Orr PH, Casper HH, Tacke BK. Potato starch paste behavior as related to some physical/chemical properties. Journal of Food Science. 1994;**59**:644-648. DOI:

[8] Sun T, Lærke HN, Jørgensen H, Bach Knudsen KE. The effect of heat processing of different starch sources on the in vitro and in vivo digestibility in growing pigs. Animal Feed Science and Technology. 2006;**131**:66-85. DOI: 10.1016/j.anifeedsci.2006.02.009

[9] Yusuph M, Tester RF, Ansell R, Snape CE. Composition and properties of starches extracted from tubers of different potato varieties grown under the same environmental conditions. Food Chemistry. 2003;**82**:283-289. DOI: 10.1016/S0308-8146(02)00549-6

[10] Noda T, Takigawa S, Matsuura-Endo C, Kim SJ, Hashimoto N, Yamauchi H, Hanashiro I, Takeda Y. Physicochemical properties and amylopectin structures of large, small, and extremely small potato starch granules. Carbohydrate Polymer. 2005;**60**:245-225. DOI:

[11] Aberle T, Burchard W, Vorwerg W, Radosta S. Conformational contributions of amylose and amylopectin to the structural properties of starches from various sources. Starch/

[12] Ratnayake WS, Jackson DS. A new insight into the gelatinization process of native starches. Carbohydrate Polymer. 2007;**67**:511-529. DOI: 10.1016/j.carbpol.2006.06.025

[13] McPherson AE, Jane J. Comparison of waxy potato with other root and tuber starches.

[14] Zhu Q, Bertoft E. Composition and structural analysis of alpha-dextrins from potato amylopectin. Carbohydrate Research. 1996;**288**:155-174. DOI: 10.1016/S0008-6215(96)90793-4

[15] Zeeman SC, Kossmann J, Smith AM. Starch: Its metabolism, evolution, and biotechnological modi cation in plants. Annual Review of Plant Biology. 2010;**61**:209-234. DOI:

Carbohydrate Polymer. 1999;**40**:57-70. DOI: 10.1016/S0144-8617(99)00039-9

Biotechnology. 2002;**20**:295-299. DOI: 10.1038/nbt0302-295

Starch. 2003;**55**:381-389. DOI: 10.1002/star.200300169

Stärke. 1994;**46**:329-335. DOI: 10.1002/star.19940460903

10.1146/annurev-arplant-042809-112301

S0144-8617(00)00260-5

10.1111/j.1365-2621.1994.tb05583.x

10.1016/j.carbpol.2005.01.015

Research. 1996;**282**:247-262. DOI: 10.1016/0008-6215(95)00381-9

### **Acknowledgements**

Authors are gratefully acknowledging the contribution of Ms. Neha Joshi, Department of Biotechnology for critically evaluating and correcting the manuscript. The DCU acknowledge the Department of Science and Technology (DST-WOS-A/LS/426/2013) for the financial assistance to conduct the experiments on similar aspect in the laboratory of Plant Molecular Biology at Department of Biotechnology, Dr Harisingh Gour Central University, Sagar, India.

#### **Author details**

Chandrama Prakash Upadhyaya\*, Deepak Singh Bagri and Devanshi Chandel Upadhyaya

\*Address all correspondence to: cpupadhyay@gmail.com

Department of Biotechnology, Dr Harisingh Gour Central University, Sagar, Madhya Pradesh, India
