Team:Nevada/Project/

iRICE: A Novel, Non-GM Approach to Biofortification of Rice
Even though white rice is a major source of calories for over half the world’s population, it is a poor source of nutrients. While rice can be fortified using vitamin powders, such approaches have had limited success because many vitamins are leeched away during the washing process prior to cooking. To address this problem, we have engineered proteins that will adhere nutrients to rice grains and prevent losses. These proteins contain a starch-binding domain that is fused to specific nutrient-binding domains. Because rice is composed mainly of starch, the starch-binding domain prevents nutrient leeching during washing. Upon cooking, the nutrient-binding domain denatures and releases the nutrients into the cooked rice. Supplementing rice with these fusion proteins will provide a novel, non-GMO approach to fortifying rice. Proteins with a starch-binding domain connected to a Vitamin b12-binding domain, a thiamine-binding domain, a lysine-rich protein, and a RFP have been created.

The Problem with Rice

From rice in fields to rice on your plate, there are numerous procedures that rice must undergo before it is ready to be eaten. The first process is called milling. Milling is the removal of the husk and bran layer of rice. The husk is the shell, a hard non-edible layer that protects the edible bran and endosperm. The bran layer is where most of the nutrition is located and most of the times removed due to taste purposes. This is where the lack of nutrition comes from, most people do not like the taste of brown rice or rice with the bran layer. Many people prefer white rice which contains virtually no nutritional value.

The Old GMO Approach to Fortification

The most modern approach to providing nutrition through food now is through genetically modifying the genetic code itself. An example of this is Golden Rice, a rice grain fortified with beta-carotene which provides vitamin A when cooked. The concept of genetically modifying is simple, simply add the genetic code for beta-carotene into the genetic code for rice and grow your vitamin A enriched rice.

The biggest problem with genetically modified organism is that most people and culture don’t accept transgenic species. Africa won’t allow transgenic grain into their continent, India refuses to eat golden colored rice, and other countries in Asia simply prefer the taste of white rice that lacks any nutrition. This is why there is a need for a new grain of rice that does not alter the natural genetic code of rice and can still provide just as much nutrition as genetically modified. This is why we developed the iRICE.

The iRICE System

Starch-Binding Protein

The starch binding gene used in this project, CBM 21, is derived from the species, R. oryzae, which is a form of fungus that thrives on dead organic matter, including starch containing species. It is part of an operon that codes for a two-domain enzyme. One domain has the catalytic function of breaking down starch while the other domain binds to the starch molecule in order to provide optimal conditions for the catalytic portion. This project takes advantage of the starch binding domain encoded by this gene and it is utilized for its ability to bind rice starch efficiently.

Customizable Constructs

The idea behind this project was to create a complex that is not only effective in nutrient enhancement but adaptable to the specific needs of various populations. The costruct consists of a starch binding protein that will adhere to (in this case) the starch in rice, and one of any number of binding proteins. This is where the customization comes in. The combinations or binding proteins you can use is diverse. In our case we have used Thiamine and Cobalamin binding proteins that will adhere available vitamins from the environment, but one could use any number of vitamin, amino acid, or pharamaceutical (speculatively) binding proteins.

Possiblility of GM utilization

Given the current opinion towards GMOs we have designed our constructs to be used as an additive that could be used in a coating or dusting process. However, the potential for GMO exists should popular opinion change in the future. Rather than create supplimental proteins that must be added in the milling process the vitamin binding proteins would be expressed by the plants themselves.

Vitamin B12-Binding Protein

Vitamin B12, Cyanocobalamin, is a vitamin involved in many neurological processes. The main source of dietary B12 is found in meat and dairy products. While it is found in plant sources, it is not biologically usable by humans or other mammals. This poses problems for those who follow vegan diets or whose main calorie source comes from non-animal products. This includes populations dependent on rice or rice products.

While deficiencies in vitamin B12 are not well documented, it is slowly becoming a more crucial problem. Often times, B12 deficiencies mimic ailments that are closely related to Alzheimer’s and dementia, or more generally, symptoms related to fatigue. It is proposed that the current recommendations in USA are on the low level, and that 40% of people between 26 and 80 are at or below this level. At these levels, symptoms begin to manifest, and, depending on the longevity of this sustained deficiency, permanent brain damage may occur. This is alarming when considering populations dependent on rice as there is no B12 present.

There are no current methods used to fortify rice with B12 which is why this project is innovative. It utilizes the starch binding capabilities of the CBM 21 gene, coding for a starch binding protein, as well as the BtuF gene coding for B12 binding protein. Together these proteins will effectively bind starch and supplement rice, or any number of starch products, with vitamin B12.

Thiamine-Binding Protein

Lysine-Rich Protein

Our Results

Proof of Concept

Red Fluorescent Protein

Red Fluorescent Protein is a protein that glows red when exposed to visible light. RFP and other fluorescent proteins are used frequently in biological experiments as marker proteins.

Results

RFP was combined with Starch binding protein successfully. The construct was used to show that the starch binding protein can bind to rice. After binding, we also used an amylase column to show binding.

Conclusions for project

Each of the proteins was expressed successfully with a starch binding domain and their nutrient binding components shown to bind their nutrient. The red fluorescent protein shows the functionality of the starch binding protein. With both domains shown to be working, our project comes to a successful close.

References