Researchers are changing potato starch with CRISPR technology – AgriLife Today

Simple potatoes are not only dietary carbohydrates for humans, they are also starches for a wide range of industrial applications. Scientists at Texas A&M AgriLife are studying how the relationship between the two starch molecules in potatoes, amylose and amylopectin, to increase both culinary and industrial applications.

Representation of the process of removing amylose starch from a potato. (Texas A&M AgriLife Chart)

For example, wax potatoes, which have a high amylopectin content, have applications in the production of bioplastics, food additives, adhesives and alcohol.

Two recently published articles International Journal of Molecular Sciences and Plant cells, tissues and organ culture journals explain how CRISPR technology can advance the use of the world’s largest vegetable crop.

Both articles cover the work of Dr. Stephany Toinga, a graduate student in Dr. Keerti Rathore’s lab at the AgriLife Research Plant Biotechnology Lab at the Texas A&M Institute of Plant Genomics and Biotechnology and the Department of Soil. and Agricultural Sciences. She also co-authored two articles with Isabel Vales, Ph.D., an AgriLife Research potato grower at the Texas Department of Horticultural Sciences. Toinga Texas is now a postdoctoral fellow at A&M AgriLife Research in Vales.

“The information and knowledge we have gained from these two studies will help us to incorporate other desirable traits into this very important crop,” Rathor said.

Potato events

Potatoes are the world’s largest vegetable crop and the third most important human food crop, after only rice and wheat. Potatoes grow in more than 160 countries on 40.8 million hectares and serve as a staple food for more than a billion people.

Since medium-sized potatoes provide about 160 calories, mostly derived from starch, tubers are an important source of energy for many people around the world, Rathore said. Potatoes also provide other necessary nutrients, including vitamins and minerals.

Potatoes are a seasonal crop that is relatively sensitive to heat and drought stress. The crop also suffers from pests such as the Colorado potato beetle, aphids and nematodes, as well as early and late blight, zebrafish, Fusarium rot and some viral diseases. Late blight was the cause of the Irish potato famine.

Starch is essential for both dietary and industrial use

The number of starches in potato tubers is the main factor that determines the use of potatoes. High-starch potatoes are often used for processed foods, such as chips, chips and dehydrated potatoes, Vales said.

A ruler sits next to different potato tubers.  They are over two inches long, about two inches long, and one root system has three microtubules.
Potato tubers edited in the Texas A&M AgriLife study. If these are placed in the soil, they will produce a normal potato plant with tubers of normal size. (Photo by Texas A&M AgriLife by Stephany Toinga)

Low- or medium-starch potatoes are often used for fresh or table stock, he said. For the fresh market, other important issues are the appearance of the tuber, including skin texture, skin color, flesh color, and tuber shape. Recently, specialties of different types of potato specialties, such as finger leeks; smaller sizes; and red, purple, or yellow skin and flesh are becoming popular for their comfort in cooking and increasing their nutritional value.

The shape of the potato is no less important for human consumption than for human consumption, Vales said. Potato tubers with heat or drought stress or external deformities caused by other factors can be used for a variety of uses, including dog and cow food. In addition, potato starch produces ethanol in fuels or beverages such as vodka; biodegradable plastic substitute; or adhesives, binders, textile agents and fillers for the pharmaceutical, textile, wood and paper industries and other sectors.

For industrial applications, the amount and type of starch in a potato are important.

Toinga said amylopectin-containing starches are desirable for processed foods and other industrial applications because of their special functional properties. For example, starches are used as stabilizers and thickeners in food products and as emulsifiers in decorative salads. Due to its freeze-thaw stability, amylopectin starch is used in frozen foods. In addition, potatoes rich in amylopectin starch provide higher levels of ethanol than other starches.

Benefits of breeding potatoes with optional starches

The development of potato crops with modified starch may open up new opportunities, Toinga said. Potatoes with high amylopectin and low amylose, like the Yukon Gold strains edited by the genes described in the International Journal of Molecular Sciences, have industrial applications beyond traditional use.

In contrast, potatoes with high amylose levels and low amylopectin would be desirable for human consumption, Vales said. Amylose acts as a fiber and does not release glucose as easily as amylopectin, so it has a lower glycemic index and potatoes are more acceptable for people with diabetes.

CRISPR / Cas9 creates new opportunities

CRISPR / Cas9 technology has expanded the range of tools available to growers, Vales said, and is a faster and faster way to incorporate the desired features into popular crop varieties. The usual growth process is a long one and can take 10-15 years.

Inside is a potato plant and a pot with small microtubules in the bottom.
A line of expulsion in the culture that has created miniature potatoes called microtubules. (Photo of Stephany Toinga by Texas A&M AgriLife)

In addition, he said, due to the complex nature of the potato genome, it is difficult to create new crops with the right complement to desirable traits for regular growth. Molecular growth has improved growth efficiencies, and gene editing using CRISPR / Cas9 technology adds another level of sophistication.

“We used the Agrobacterium method to deliver CRISPR reagents to potatoes because they are the most reliable, efficient, and most expensive method of delivery compared to all other delivery methods,” Rathore said.

In the first study, highlighted Plant cells, tissues and organ culture In the article, a potato line with four copies of gfp, a jellyfish gene that allows visualization based on gene activity fluorescence, was used for the mutation-oriented CRISPR / Cas9 system, Toinga said.

Essentially, this project provided an easy-to-see feature that allowed researchers to optimize the methodology.

“The loss of the green fluorescence trait and sequencing of the gfp gene after CRISPR treatment indicated that it was possible to disrupt four copies of the gfp gene, thus confirming that it would be possible to mutate four alleles of a native gene in the tetraploid.”

Improved Yukon Gold cultivar

Of the potato crops evaluated in the first study, the Yukon Gold strain was best recreated, so it was used for the second study. In the study described in the second round International Journal of Molecular SciencesThe Yukon Gold tetraploid gbss native gene was aimed at effectively eliminating amylose. The result was a potato rich in amylopectin and low in starch.

“One of the knockout events, T2-7, showed normal growth and performance characteristics, but it was completely without amylose,” Toinga said.

This tuber starch, T2-7, can be found in industrial applications in the paper and textile sectors, such as adhesives / binders, bioplastics and ethanol. The tuber starch in this experimental strain, due to its freeze-thaw stability, should also be useful for the production of frozen foods without the need for chemical changes. Potatoes containing amylopectin as the exclusive form of starch should provide more ethanol for industrial use or for the production of alcoholic beverages.

As a next step in this research, the T2-7 strain has been self-pollinated and crossed with the Yukon Gold strain donor and other potato clones to eliminate transgenic elements.

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