The Multiplanetary Future of Plant Synthetic Biology

Green horizons: how plant synthetic biology can enable space exploration and drive on Earth sustainability

As humanity looks towards expanding activity from low Earth orbit to the Moon and beyond, resource use efficiency and self-sustainability will be critical to ensuring success in the long term. Furthermore, solutions developed for the stringent requirements of space will be equally valuable in meeting sustainability goals here on Earth. Advances in synthetic biology allow us to harness the complex metabolism of life to produce the materials we need in situ. Translating those lessons learned from microbial systems to more carbon-efficient photosynthetic organisms is an area of growing interest. Plants can be engineered to sustainably meet a range of needs, from fuels to materials and medicines.

Phosphorus-solubilizing bacteria improve the growth of Nicotiana benthamiana on lunar regolith simulant by dissociating insoluble inorganic phosphorus

In-situ utilization of lunar soil resources will effectively improve the self-sufficiency of bioregenerative life support systems for future lunar bases. Therefore, we have explored the microbiological method to transform lunar soil into a substrate for plant cultivation. In this study, five species of phosphorus-solubilizing bacteria are used as test strains, and a 21-day bio-improving experiment with another 24-day Nicotiana benthamiana cultivation experiment are carried out on lunar regolith simulant. We have observed that the phosphorus-solublizing bacteria Bacillus mucilaginosus, Bacillus megaterium, and Pseudomonas fluorescens can tolerate the lunar regolith simulant conditions and dissociate the insoluble phosphorus from the regolith simulant. The phosphorus-solubilizing bacteria treatment improves the available phosphorus content of the regolith simulant, promoting the growth of Nicotiana benthamiana. Here we demonstrate that the phosphorus-solubilizing bacteria can effectively improve the fertility of lunar regolith simulant, making it a good cultivation substrate for higher plants. The results can lay a technical foundation for plant cultivation based on lunar regolith resources in future lunar bases.

How to make the Lunar and Martian soils suitable for food production - Assessing the changes after manure addition and implications for plant growth

The in-situ resource utilisation (ISRU), in terms of native rocky materials and astronaut wastes, is crucial in contests of soil-based space-farming. Nevertheless, extra-terrestrial soils are very different from Earth soils, lacking any form of organic carbon and associated macro and micronutrients. In this research, we aimed to study and modify two commercially available Lunar and Martian regolith simulants (LHS-1 from Exolith Lab and MMS-1 from Martian Garden) to make them an adequate medium for plant growth. Lettuce was chosen as reference crop to guide the discussion on the results obtained. To reach this main objective, we added to simulants a commercially available monogastric-based organic manure chosen as a substitute of a possible organic amendment produced onboard. The simulant/manure mixture rates were 100:0, 90:10, 70:30, 50:50; w:w. As expected, an approximately linear increase of total and bioavailable contents of macro (N, S, P, Ca, K, Mg) and micro (Fe, Mn, Cu, Zn) nutrients with increasing manure addition to simulants was observed. On the other hand, the very high pH of manure (pH, 9.02) along with its salinity (EC, 6.7 dS m-1) and sodicity (Na, 5.3 g kg-1), did not correct the already high pH of simulants (very high for LHS-1), but rather raised their soluble salt content and sodium amount on the exchange complex. In addition, an increase of toxic soluble aluminium and heavy elements (Pb, Ni, Cr, V) was observed, mainly in the strongly alkaline lunar simulant/manure mixtures. The addition of an organic source also produced a generalised improvement of water retention and hydraulic conductivity of both regolith simulants, in proportion to the percentage of manure addiction. For both situations, the best mixture ratio was 70:30. In terms of water retained, the LHS-1 mixtures benefited more than the MMS-1 ones by manure addition since water was held more in the "dry" (between -100 and -600 cm of matric potential head) than in the "humid" (between -25 and -100 cm of matric potential head) region of water retention. This would make LHS-1 mixtures more useful for cultivation of lettuce, at least in terms of physico-hydraulic properties. Nevertheless, the overall characterisation of the mixtures unveiled that MMS-1-based substrates can ensure better agronomic performances than LHS-1 ones, mainly due to lower pHs and higher nutrient availability; this divergent fertility was particularly evident at 90:10 simulant/manure rate and tend to be mitigated by increasing the levels of manure.

A molecular study of Italian ryegrass grown on Martian regolith simulant

In the last decade, the exploration of deep space has become the objective of the national space programs of many countries. The International Space Exploration Coordination Group has set a roadmap whose long-range strategy envisions the expansion of human presence in the solar system to progress with exploration and knowledge and to accelerate innovation. Crewed missions to Mars could be envisaged by 2040. In this scenario, finding ways to use the local resources for the provision of food, construction materials, propellants, pharmaceuticals is needed. Plants are important resources for deep space manned missions because they produce phytochemicals of pharmaceutical relevance, are sources of food and provide oxygen which is crucial in bioregenerative life support systems. Growth analysis and plant biomass yield have been previously evaluated on Martian regolith simulants; however, molecular approaches employing gene expression analysis and proteomics are still missing. The present work aims at filling this gap by providing molecular data on a representative member of the Poaceae, Lolium multiflorum Lam., grown on potting soil and a Martian regolith simulant (MMS-1). The molecular data were complemented with optical microscopy of root/leaf tissues and physico-chemical analyses. The results show that the plants grew for 2 weeks on regolith simulants. The leaves were bent downwards and chlorotic, the roots developed a lacunar aerenchyma and small brownish deposits containing Fe were observed. Gene expression analysis and proteomics revealed changes in transcripts related to the phenylpropanoid pathway, stress response, primary metabolism and proteins involved in translation and DNA methylation. Additionally, the growth of plants slightly but significantly modified the pH of the regolith simulants. The results here presented constitute a useful resource to get a comprehensive understanding of the major factors impacting the growth of plants on MMS-1.

Unearthing terrestrial extreme microbiomes for searching terrestrial-like life in the Solar System

The possibility of life elsewhere in the universe has fascinated humankind for ages. To the best of our knowledge, life, as we know it, is limited to planet Earth; yet current investigation suggests that life might be more common than previously thought. In this review, we explore extreme terrestrial analogue environments in the search for some notable examples of extreme organisms, including overlooked microbial groups such as viruses, fungi, and protists, associated with limits of life on Earth. This knowledge is integral to provide the foundational principles needed to predict what sort of Earth-like organisms we might find in the Solar System and beyond, and to understand the future and origins of life on Earth.

Harnessing bioengineered microbes as a versatile platform for space nutrition

Human enterprises through the solar system will entail long-duration voyages and habitation creating challenges in maintaining healthy diets. We discuss consolidating multiple sensory and nutritional attributes into microorganisms to develop customizable food production systems with minimal inputs, physical footprint, and waste. We envisage that a yeast collection bioengineered for one-carbon metabolism, optimal nutrition, and diverse textures, tastes, aromas, and colors could serve as a flexible food-production platform. Beyond its potential for supporting humans in space, bioengineered microbial-based food could lead to a new paradigm for Earth's food manufacturing that provides greater self-sufficiency and removes pressure from natural ecosystems.

Bioactive Compounds and Antioxidant Activity of Lettuce Grown in Different Mixtures of Monogastric-Based Manure With Lunar and Martian Soils

The supplementation of bioactive compounds in astronaut's diets is undeniable, especially in the extreme and inhospitable habitat of future space settlements. This study aims to enhance the Martian and Lunar regolith fertility (testing two commercial simulants) through the provision of organic matter (manure) as established by in situ resource utilization (ISRU) approach. In this perspective, we obtained 8 different substrates after mixing Mojave Mars Simulant (MMS-1) or Lunar Highlands Simulant (LHS-1), with four different rates of manure (0, 10, 30, and 50%, w/w) from monogastric animals. Then, we assessed how these substrates can modulate fresh yield, organic acid, carotenoid content, antioxidant activity, and phenolic profile of lettuce plants (Lactuca sativa L.). Regarding fresh biomass production, MMS-1-amended substrates recorded higher yields than LHS-1-ones; plants grown on a 70:30 MMS-1/manure mixture produced the highest foliar biomass. Moreover, we found an increase in lutein and β-carotene content by + 181 and + 263%, respectively, when applying the highest percentage of manure (50%) compared with pure simulants or less-amended mixtures. The 50:50 MMS-1/manure treatment also contained the highest amounts of individual and total organic acids, especially malate content. The highest antioxidant activity for the ABTS assay was recorded when no manure was added. The highest content of total hydroxycinnamic acids was observed when no manure was added, whereas ferulic acid content (most abundant compound) was the highest in 70:30 simulant/manure treatment, as well as in pure LHS-1 simulant. The flavonoid content was the highest in pure-simulant treatment (for most of the compounds), resulting in the highest total flavonoid and total phenol content. Our findings indicate that the addition of manure at specific rates (30%) may increase the biomass production of lettuce plants cultivated in MMS-1 simulant, while the phytochemical composition is variably affected by manure addition, depending on the stimulant. Therefore, the agronomic practice of manure amendment showed promising results; however, it must be tested with other species or in combination with other factors, such as fertilization rates and biostimulants application, to verify its applicability in space colonies for food production purposes.

Response and tolerance mechanism of food crops under high temperature stress: a review

High temperature stress events are critical factors inhibiting crop yield. Meanwhile, world population is growing very rapidly and will be reached up to 9 billion by 2050. To feed increasing world population, it is challenging task to increase about 70% global food productions. Food crops have significant contribution toward global food demand and food security. However, consequences from increasing heat stress events are demolishing their abilities to survive and sustain yield when subjected to extreme high temperature stress. Therefore, there is dire need to better understand response and tolerance mechanism of food crops following exposure to heat stress. Here, we aimed to provide recent update on impact of high temperature stress on crop yield of food crops, pollination, pollinators, and novel strategies for improving tolerance of food crop under high temperature stress. Importantly, development of heat-resistant transgenic food crops can grant food security through transformation of superior genes into current germplasm, which are associated with various signaling pathways as well as epigenetic regulation in response to extreme high temperature stress.

Homecoming: rewinding the reductive evolution of the chloroplast genome for increasing crop yields

Developing more productive and sustainable crops will be essential to achieving food security in coming decades. A core process in plant evolution has been the transfer of chloroplast-encoded genes to the nuclear genome. We propose reverting this process as a new approach to improve plant disease resistance and photosynthesis in future crops.

Bioinformational trends in grape and wine biotechnology

The creative destruction caused by the coronavirus pandemic is yielding immense opportunity for collaborative innovation networks. The confluence of biosciences, information sciences, and the engineering of biology, is unveiling promising bioinformational futures for a vibrant and sustainable bioeconomy. Bioinformational engineering, underpinned by DNA reading, writing, and editing technologies, has become a beacon of opportunity in a world paralysed by uncertainty. This article draws on lessons from the current pandemic and previous agricultural blights, and explores bioinformational research directions aimed at future-proofing the grape and wine industry against biological shocks from global blights and climate change.

Molecular pharming to support human life on the moon, mars, and beyond

Space missions have always assumed that the risk of spacecraft malfunction far outweighs the risk of human system failure. This assumption breaks down for longer duration exploration missions and exposes vulnerabilities in space medical systems. Space agencies can no longer reduce the majority of the human health and performance risks through crew members selection process and emergency re-supply or evacuation. No mature medical solutions exist to address this risk. With recent advances in biotechnology, there is promise for lessening this risk by augmenting a space pharmacy with a biologically-based space foundry for the on-demand manufacturing of high-value medical products. Here we review the challenges and opportunities of molecular pharming, the production of pharmaceuticals in plants, as the basis of a space medical foundry to close the risk gap in current space medical systems. Plants have long been considered to be an important life support object in space and can now also be viewed as programmable factories in space. Advances in molecular pharming-based space foundries will have widespread applications in promoting simple and accessible pharmaceutical manufacturing on Earth.

Plant Biosystems Design Research Roadmap 1.0

Human life intimately depends on plants for food, biomaterials, health, energy, and a sustainable environment. Various plants have been genetically improved mostly through breeding, along with limited modification via genetic engineering, yet they are still not able to meet the ever-increasing needs, in terms of both quantity and quality, resulting from the rapid increase in world population and expected standards of living. A step change that may address these challenges would be to expand the potential of plants using biosystems design approaches. This represents a shift in plant science research from relatively simple trial-and-error approaches to innovative strategies based on predictive models of biological systems. Plant biosystems design seeks to accelerate plant genetic improvement using genome editing and genetic circuit engineering or create novel plant systems through de novo synthesis of plant genomes. From this perspective, we present a comprehensive roadmap of plant biosystems design covering theories, principles, and technical methods, along with potential applications in basic and applied plant biology research. We highlight current challenges, future opportunities, and research priorities, along with a framework for international collaboration, towards rapid advancement of this emerging interdisciplinary area of research. Finally, we discuss the importance of social responsibility in utilizing plant biosystems design and suggest strategies for improving public perception, trust, and acceptance.

An Oxygen Delivery Polymer Enhances Seed Germination in a Martian-like Environment

Critical to the success of establishing a sustainable human presence on Mars is the ability to economically grow crop plants. Several environmental factors make it difficult to fully rely on local resources for agriculture. These include nutrient sparse regolith, low and fluctuating temperatures, a high amount of ultraviolet radiation, and water trapped locally in the form of ice or metal oxides. While the 96% CO2 martian atmosphere is ideal to support photosynthesis, high CO2 concentrations inhibit germination. An added difficulty is the fact that a vast majority of crop plants require oxygen for germination. Here, we report the production of a polymer-based oxygen delivery system that supports the germination and growth of cress seeds (Lepidium sativum) in a martian regolith simulant under a martian atmosphere at 101 kPa. The oxygen-donating system is based on a low-density lightly cross-linked polyacrylate that is foamed and converted into a dry powder. It is lightweight, added in low amounts to regolith simulant, and efficiently donates enough oxygen throughout the volume of hydrated regolith simulant to fully support seed germination and plant growth. Germination rates, plant development, and plant mass are nearly identical for L. sativum grown in 100% CO2 in the presence of the oxygen-donating lightly cross-linked polyacrylate compared with plants grown in air. The polymer system also serves to protect root structures and better anchors plants in the regolith simulant.

Mars Regolith Simulant Ameliorated by Compost as in situ Cultivation Substrate Improves Lettuce Growth and Nutritional Aspects

Heavy payloads in future shuttle journeys to Mars present limiting factors, making self-sustenance essential for future colonies. Therefore, in situ resources utilization (ISRU) is the path to successful and feasible space voyages. This research frames the concept of planting leafy vegetables on Mars regolith simulant, ameliorating this substrate’s fertility by the addition of organic residues produced in situ. For this purpose, two butterhead lettuce (Lactuca sativa L. var. capitata) cultivars (green and red Salanova^®) were chosen to be cultivated in four different mixtures of MMS-1 Mojave Mars simulant:compost (0:100, 30:70, 70:30 and 100:0; v:v) in a phytotron open gas exchange growth chamber. The impact of compost rate on both crop performance and the nutritive value of green- and red-pigmented cultivars was assessed. The 30:70 mixture proved to be optimal in terms of crop performance, photosynthetic activity, intrinsic water use efficiency and quality traits of lettuce. In particular, red Salanova^® showed the best performance in terms of these quality traits, registering 32% more phenolic content in comparison to 100% simulant. Nonetheless, the 70:30 mixture represents a more realistic scenario when taking into consideration the sustainable use of compost as a limited resource in space farming, while still accepting a slight significant decline in yield and quality in comparison to the 30:70 mixture.

Synthetic Biology for Terraformation Lessons from Mars, Earth, and the Microbiome

What is the potential for synthetic biology as a way of engineering, on a large scale, complex ecosystems? Can it be used to change endangered ecological communities and rescue them to prevent their collapse? What are the best strategies for such ecological engineering paths to succeed? Is it possible to create stable, diverse synthetic ecosystems capable of persisting in closed environments? Can synthetic communities be created to thrive on planets different from ours? These and other questions pervade major future developments within synthetic biology. The goal of engineering ecosystems is plagued with all kinds of technological, scientific and ethic problems. In this paper, we consider the requirements for terraformation, i.e., for changing a given environment to make it hospitable to some given class of life forms. Although the standard use of this term involved strategies for planetary terraformation, it has been recently suggested that this approach could be applied to a very different context: ecological communities within our own planet. As discussed here, this includes multiple scales, from the gut microbiome to the entire biosphere.

The Synthetic Biology Toolkit for Photosynthetic Microorganisms

Photosynthetic microorganisms offer novel characteristics as synthetic biology chassis, and the toolbox of components and techniques for cyanobacteria and algae is rapidly increasing.

Harnessing synthetic biology for kelp forest conservation1

Environmental and climatic change is outpacing the ability of organisms to adapt, at an unprecedented level, resulting in range contractions and global ecosystem shifts to novel states. At the same time, scientific advances continue to accelerate, providing never-before imagined solutions to current and emerging environmental problems. Synthetic biology, the creation of novel and engineered genetic variation, is perhaps the fastest developing and transformative scientific field. Its application to solve extant and emerging environmental problems is vast, at times controversial, and technological advances have outpaced the social, ethical, and practical considerations of its use. Here, we discuss the potential direct and indirect applications of synthetic biology to kelp forest conservation. Rather than advocate or oppose its use, we identify where and when it may play a role in halting or reversing global kelp loss and discuss challenges and identify pathways of research needed to bridge the gap between technological advances and organismal biology and ecology. There is a pressing need for prompt collaboration and dialogue among synthetic biologists, ecologists, and conservationists to identify opportunities for use and ensure that extant research directions are set on trajectories to allow these currently disparate fields to converge toward practical environmental solutions.

Plant synthetic biology could drive a revolution in biofuels and medicine

Population growth, climate change, and dwindling finite resources are amongst the major challenges which are facing the planet. Requirements for food, materials, water, and energy will soon exceed capacity. Green biotechnology, fueled by recent plant synthetic biology breakthroughs, may offer solutions. This review summarizes current progress towards robust and predictable engineering of plants. I then discuss applications from the lab and field, with a focus on bioenergy, biomaterials, and medicine.