Description

Rising Temperatures: a Global Food Security Crisis

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It is widely known that global temperatures are increasing over time: annual temperatures have been on the rise by 0.18°C since 1981^[1]. The average annual temperature in Canada has increased 1.7°C from 1948 to 2016^[2]. The average annual temperature is changing even more rapidly in Northern Canada.

In parallel, British Columbia (BC) has been experiencing increased heat wave events, with 2021 having one of the most fatal and severe periods of heat with 619 fatalities in a 6-day period^[15]. Increased temperatures of a region can lead to several negative impacts including^[2]:

• Reduced agricultural crop yields.
• Increased cases of heat-related illness and death.
• Increased electricity costs to pay for cooling systems in homes and buildings.
• Increased risk of drought, heat waves, and wildfires.
• Increased risk of food and water-borne illnesses.
• Infrastructure collapse in regions that rely on ice roads.

In a 2021 report by the Food and Agriculture Organization (FAO), moderate or severe food insecurity worldwide has been increasing, from 22.6% of the population in 2014 rising up to 30.4% in 2020 with the onset of the COVID-19 pandemic^[3]. As of 2018, 12.7% of Canadian households face food insecurities^[4]. While there are a myriad of contributors to food insecurity – reduced agricultural crop yields can be a major contributor. Decreases in crop yield have the potential to lead to increased food prices, which could amplify pre-existing food insecurities. Food security is a key determinant of people’s health.

Our team set about to use a synthetic biology solution to address the one of the negative impacts of increasing global temperatures: reduced agricultural crop yields. This will also act to reduce or mitigate food insecurities.

Wheat: a Universal Staple Crop

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Wheat-derived food products play a large part in human nutrition worldwide. As such, a great proportion of food insecurity can be resolved through engineering value-added wheat given its strong integration into citizens’ calorie consumption. Within all the grains, wheat specifically is suffering effects of heat stress, justifying the need for creating a solution for this crop. Wheat production in Canada was down 38.5% in 2021 compared to 2020, most likely due to drought and increased temperatures^[2]. For canola, another grain, production also fell 35.4% in 2021. These were the lowest wheat and canola crop yields since 2007^[6]. Other grains like oats and barley also saw a crop decrease in Canada in 2021.

The optimal growth temperature for wheat is between 17 to 23°C, with the most optimal temperature being 15°C. Above this temperature results in a decrease in yield of 3-4%^[7]. The average temperature during the period that wheat has traditionally been grown in has been increasing yearly, and falls outside of this range (Figure 1), with these temperatures expected to increase in the coming years. The drastic economic effects are already being observed: earlier this year, India was forced to halt wheat exports in order to supply domestic demand in face of reduced yields due to spring heat waves^[8].

Elevated Temperatures and Wheat

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Molecular Effects of Heat Stress

Heat stress affects crop and wheat yields through both molecular and physiological processes. Molecular-level processes that are interrupted by heat are relevant to both the nutritional value and the overall yield of the wheat, resulting in decreased productivity or lower quality. For example, starch synthesis, which is of interest in bread production and nutritional value, is limited during heat stress through denaturation of the soluble enzyme starch synthase. One study found a -11.24 fold change of this enzyme in developing wheat seeds at heat stress treatments of 37 to 42°C, along with a decrease in other carbohydrate metabolism proteins such as sucrose synthase and triose phosphate isomerase^[10]. Overexpression of alpha-amylase, the enzyme responsible for initiating starch degradation, has been found in heat-stressed wheat during flowering^[11]. This further emphasizes the detrimental effect of heat stress on starch synthesis, which is essential for proper wheat structure and function.

Physiological Effects of Heat Stress

Molecular alterations resulting from heat stress outlined above in turn affect physiological processes that result in decreased nutritional and economic outcomes. Heat stress conditions have been correlated to weaker dough properties such as faster dough breakdown and shorter extension time. Flour contaminated with 5-10% of overexpressed alpha-amylase wheat lowers its value below acceptable thresholds for bulk commodities^{[11, 12]}.

Heat stress also results in oxidative stress and consequent production of reactive oxygen species, damaging thylakoid membrane structure and photosystem II activity, in turn affecting photosynthetic rate^[9].

Current Strategies & Solutions

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As seen in the section above, elevated temperatures decrease wheat yield by damaging essential physiological processes and also decrease the nutritional value of this reduced yield. The detrimental effects of heat on plants, particularly such an essential one like wheat, harbours the need to develop solutions to increase food security in the face of such drastic climate change-driven issues. Our project’s proposal involves engineering a variety of wheat that is able to express several factors to offset heat stress.

Current strategies for mitigating heat-related crop losses:^[12]

• Selecting heat-resistant varieties amongst less heat-resistant varieties.
• Breeding wheat plants for increased heat tolerance traits.
• Careful irrigation and sowing to minimize water loss.
• Seed inoculation with rhizobacteria to increase heat tolerance.

Limitations to current strategies:

• Genetic manipulation (breeding varieties), changing irrigation, and sowing methods can be time consuming to farmers, as well as expensive.
• Modifying sowing time may affect overall wheat hardiness.
• Changing the variety of wheat planted might affect the taste of the wheat and downstream customer satisfaction.
• High cost of certain novel applications make them less economically accessible for smaller farming companies to implement.
• An ideal solution to the problem won’t create extra work or a significant increase in cost for farmers.

Our project aimed to address this issue by creating a genetically engineered wheat strain that would be more tolerant to heat stress. HB4 wheat is a currently existing genetically modified wheat strain for drought conditions which has been successfully approved for use in Argentina, but not in Canada. We hope our project could provide a similar solution in Canada for heat conditions^[12].

Our Project's Overarching Goals

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1. Design a genetic circuit that is inducible by heat in wheat plants.
2. Engineer wheat plants to reverse or prevent the negative molecular and/or physiological effects of heat stress.
3. Consider the downstream applications of our design for large-scale usage in the agricultural industry.

For a detailed description of our biological design, please visit our Design page. Please visit our Implementation page to learn more about the downstream applications and biosafety of our project.

Summary

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• Global temperatures are rising.
• Higher temperatures reduce agriculture crop yields due to heat negatively impacting both molecular and physiological processes of plants.
• Reduced agriculture yields can lead to increased food prices and can magnify food insecurity.
• Wheat is an important agricultural crop in Canada, where our team is located, which is why we decided to focus on this crop for our project.