Hydroponics is the future of agriculture. Compared to traditional farming, hydroponics demands less maintenance, fewer resources, and most importantly, less land. It is a rapidly growing industry that is projected to be a $31.4 billion global market by 2022, with a growth rate of 6.7% annually . As the population inches ever closer to carrying capacity, as the resources become ever scarcer, and as the climate becomes ever warmer, hydroponics is the most promising solution to ensure a sustainable world - one where no one is left hungry.
But despite its immense potential, hydroponics is severely limited by diseases, nutrient imbalances, and other environmental stresses. In particular, the levels of reactive oxygen species (ROS) are known for affecting crop growth by hindering nutrient uptake, damaging cellular structures, and inducing undesirable immune responses . Even though the current market offers technologies that can measure oxidative stress, they are often fragile, expensive, and lacking spatial resolution. Moreover, little effort has been made to improve existing technologies.
At Cornell iGEM, we believe that we can do better.
ROS may be notorious for being correlated with cancer and aging, but perhaps paradoxically, research has also shown that a sufficient level of oxidative stress is critical to the growth and survival of any organism, whether it’s bacteria, humans, or plants . Therefore, the essence of successful hydroponics is not the removal of all external stress, but rather its optimization. We seek to control oxidative stress - to respond to any minute change in the environment rapidly and efficiently, and to modulate the ideal equilibrium state for each and every crop. We accomplish this feat through a novel platform with dual functionality. First, the platform allows for real-time, biologically-relevant reporting of the environmental oxidative stress via redox-sensitive fluorescent proteins. Second, it employs an optogenetic circuit to express, with great precision, a panel of enzymes that can regulate oxidative stress through the breakdown of ROS. Our synthetic biology approach combines the advantages of native ROS-sensing pathways and existing technologies while mitigating their drawbacks; it is a system that is cost-efficient and self-sustaining, while also offering greater sensitivity, versatility, and spatial resolution.
This platform is incomplete without a mechanism that can integrate our real-time reporting signal with the regulatory enzymatic output. Through extensive collaborations with a startup incubator and with invaluable feedback from hydroponic farmers, we developed a specialized optics-based technology that can accurately interpret oxidative stress reporting and precisely regulate gene transcription on an industrial scale. This technology shifts power from nature to farmers; we give farmers the tools to monitor each and every crop, as well as the ability to control environmental parameters at leisure and at will. The farmers benefit from increased crop yields and profits. The world benefits from economic stimulation and increased food supply.
Climate change, environmental destruction, and resource allocations are imminent threats to a growing population and a deteriorating world, and hydroponics offers a promising path to address those global issues. At Cornell iGEM, we are committed to engineering innovative, practical solutions to unlock the full potential of hydroponics. Through hydroponics, we create a future of sustainability that is only possible with synthetic biology.
Oxidative stress is defined as a disturbance in the balance of reactive oxygen species (ROS), and antioxidant defenses . It plays a critical role in many biological processes, the most significant of which (with respect to plants) are pathogen defense , programmed cell death , and cell to cell signaling . More recent studies have linked ROS to nutrient uptake in a beneficial capacity . In opposition to these benefits, however, too high a level of oxidative stress is lethal to most organisms as it leads to unspecific oxidation of proteins and membrane lipids, as well as DNA injury . Furthermore, tissues exposed to high levels of oxidative stress show an increased production of ethylene  which can be detrimental to the plant.
Because of the diversity of roles played by oxidative stress in biological systems, its optimization is a logical choice for anyone interested in increasing yields in agriculture. Finally, it is not sufficient to simply rely upon plants’ evolutionary response mechanisms to oxidative stress as reproductive efficiency does not necessarily correlate directly to growth or crop production. Thus there is a niche yet to be filled in optimizing this parameter.
Hydroponics is by far the most logical first choice for implementing such a system. First, the systems are highly engineered, so altering nutrient concentration, pH, or, in this case, oxidative stress, is standard for the industry. Second, most systems are entirely dark so as to minimize algal growth, meaning that a fluorescence based reporter would have almost no outside interference. Finally, when exposed to external stressors, plants will often time produce ROS themselves, further altering this balance . In a hydroponic system, this is compounded by the vast number of plants packed tightly together in space. Thus, hydroponics is the most logical choice of industry to begin with in terms of oxidative stress regulation.
Currently, no method of oxidative stress detection and regulation is consistently employed as an industry standard. Part of this is because research regarding the role of stressors in plants is relatively novel. The largest issue of this technology being adopted is simply a lack of awareness about the issue, plants regularly deal employ internal pathways to mitigate the amount of oxidative stress, so the concept of adjusting these levels artificially is new. Even if farmers wanted to optimize this parameter, they would be hard pressed to do so as current methods are expensive and lack spatial resolution. The best one could do with existing technology on the market today would be to buy a mechanical probe and add oxidants manually, with is both inaccurate and extremely inefficient in both time and cost.
The potential of Cornell iGEM’s novel technology extends far beyond increasing hydroponic yields in an industrial setting. In the simplest terms, the ability to simultaneously sense, report, and mediate oxidative stress greatly facilitates research into the roles of ROS in multitudes of biological processes including but not limited to tumor angiogenesis, aging, and diseases from a medical perspective, as well as bioreactor designs and environmental pollution from industrial and environmental perspectives.
A potential direction that we considered was engineering a direct link between the emission of a fluorescent protein to the optogenetic promoter system. If the emission wavelength of rxRFP is exactly the excitation wavelength of the optogenetic system, a feedback mechanism akin to quorum sensing could be developed, resulting in a highly sophisticated tool for bacterial communication. In order to achieve this, one would need to alter the primary structure of rxRFP to effect a shift in the emission spectra. Although this would be difficult and somewhat unpredictable, there is precedent for altering the emission spectra .
More generally, this platform is a mechanism by which transcription can be regulated with high precision by virtue of a two-step input. One application of this platform that we envision is a novel therapy for cancer. Tumors often contain a heterogenous group of cells that experience different redox states that is at least partially a function of the cell’s malignancy. This platform will allow for precise, dose-dependent responses based on the redox states of individual cells.
We also envision the use of this platform in industrial bioreactor designs, where oxidative stress can severely hinder reaction efficiencies. A redox-sensitive fluorescent output will be able to report specific regions within the bioreactors that experience abnormally high levels of stress with high temporal and spatial resolution.
This platform is a novel approach to many challenging problems that we face in medicine, agriculture, industry, environment, and research. Although it is still in early stages of development, refinement and optimization of this platform has significant implications.
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