Synthetic biology can help us to secure a sustainable food supply. Huw Jones of Rothamsted Research explains all.
In the same way that Alec Issigonis first conceptualised, drew and then built the iconic Mini, I predict it will not be long before crop plants are designed and built, bottom up, using the principles of synthetic biology.
Plant breeding using classical, top-down or forward genetic approaches has served us well in the millennia since people settled in agricultural communities and started crossing plants, selecting individuals with traits that made farming easier and the edible parts more nutritious.
But it is slow, unpredictable and limited by the variation available in the breeders’ gene pool. If the rate of extreme weather events (PDF, 1.5MB) continues increasing, breeding based on currently available genetic variation and forward genetics approaches will struggle to provide predictably high crop yields that are resilient to future climate change in the time frames required.
An alternative to top-down genetic crop improvement is the so called ‘reverse genetic’ approach. Reverse genetic utilises defined genetic cassettes – like an album of genes – that are engineered and inserted into plants to test their function and ultimately used to improve crops.
We are not there yet, but the concept of designing a theoretical crop ideotype to cope with a specific set of abiotic challenges, then using principles of synthetic biology to piece together the genetic elements necessary to encode the design is not so fanciful.
Building the best with the best
Over the last decade or so, the explosion in outputs of DNA sequencing, bioinformatics and modern molecular genetics has given us a fundamentally new understanding of the breeding process.
Firstly, it has revealed the key steps in the historic domestication of our key crop species. We now retrospectively understand the specific gene combinations that were selected thousands of years ago that drove the step-change improvements in, for instance, seed/pod shattering, height, dormancy, flowering time, seed size etc. that turned wild plants into successful, high-yielding agricultural crops.
Secondly, as this knowledge of structure-function relationships in plant genomes becomes increasingly refined, it opens the possibility of completely redesigning new crops from scratch.
Synthetic biology is the fusion of biology and engineering and is currently most advanced in bacteria. A watershed publication in 2010 described the chemical synthesis of around 1000 genes which were inserted into an ‘empty’ bacterial cell and ‘activated’ to create a free-living, self-replicating organism for the first time. In many laboratories around the world the genome of the bacterium E. coli, a research workhorse, has been successfully modified using numerous genetic modules developed using principles of synthetic biology. Probably the most commercially significant is the inclusion of a gene cassette to drive the synthesis of human insulin in E. coli or an alternative cell culture system.
Breeding climate-smart crops
Of course, there is some way to go from building genomes from scratch and expressing the resulting proteins in bacteria, or yeast, and doing the same in the higher plants. But I believe it is possible, well within our lifetimes, and desirable.
Why? Because there is good evidence that severe heat and flooding are becoming more frequent as a result of climate change. The effect of abiotic stresses such as heat and drought can lead to major spikes in food prices and combined with other social factors, such as major social unrest. In 2010 a prolonged period of heat in Russia, the world’s fourth-largest wheat exporter, accounting for roughly 14% of the global wheat trade, resulted in an emergency ban on all wheat exports. This, alongside other factors like low global yields and commodity trading, led to a spike in food prices that many linked directly to the Arab Spring uprisings where ‘bread helmets’ were worn by protestors.
It’s all too easy to think that it won’t happen again, but it will, by political and/or biological means. For instance, heat stress around flowering is predicted to increase significantly and is likely to result in considerable yield losses for heat sensitive wheat cultivars commonly grown in north Europe.
In predictable conditions, farmers aim to sow their crops to avoid the period of anthesis (when plants make and shed pollen) clashing with such extremes. However, this is becoming increasingly difficult. Thus there is a pressing need to rapidly develop crops that have different flowering times that synchronise with local temperature patterns and which are sufficiently resilient (PDF) to maintain predictable and sustainable high yields, even if these weather events vary unpredictably.
But classical breeding is a slow process. It takes at least ten years from initial crosses, which largely dictate the genetic variation captured, to the eventual marketing of a new wheat variety. On its own, this forward genetic approach is unlikely to be sufficiently speedy or responsive enough to deliver the future new varieties necessary in a changeable climate.
The current polarised debate on conventional genetic modification shows that major innovation in crop breeding must be done in a managed, safe and responsible way, with careful risk assessment and regulatory oversight to meet the needs of tomorrow’s growers and consumers.
However, as our current varieties come under increasing pressure from environmental stressors, I foresee a time when crop improvement will need to adopt the principles of reverse genetics and synthetic biology, using libraries of safe, pre-validated genetic components with known functions ready to integrate into a grab-and-grow approach to plant breeding.
About Huw Jones
Huw Jones has held his current post at Rothamsted Research, focusing on plant molecular genetics and cereal biotechnology, since 1998 and prior to that worked at Long Ashton Research Station, Bristol. His laboratory occupies a leading position in the development of cereal transformation systems and the application of transgenic approaches to study gene function. He has held two Defra licences for non-commercial field trials of GM wheat in the UK (including the aphid-resistant GM wheat field experiment recently completed). He is an Honorary Professor in the School of Biosciences, The University of Nottingham and a member of the GMO panel, European Food Safety Authority. He has published over 95 research papers, books and other articles.