Over the last decade or so, the explosion in outputs of DNA sequencing, bioinformatics and modern molecular genetics opens the possibility of completely redesigning new crops from scratch.
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. But it is slow, unpredictable and limited by the variation available in the breeders’ gene pool. If the rate of extreme weather conditions continues to increase, 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 utilizes 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 in combination with synthetic biology, to piece together the genetic elements necessary to encode the design, is not so fanciful.
We now retrospectively understand the specific gene combinations that were selected thousands of years ago.
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.
There is some way to go from building genomes from scratch and expressing the resulting proteins in the higher plants.
Synthetic biology is the fusion of biology and engineering and is currently most advanced in bacteria. In 2010 Science published an article on 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.
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 Dr. Huv Jones, Senior Research Scientist from Rothamsted Research believes it is possible, well within our lifetimes, and desirable in order to avoid future yield losses.
The current polarized 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, Dr. Jones foresees 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.
By Jana Erjavec, PhD, BioSistemika LLC
Original article by Dr. Huw Jones of Rothamsted Research