Scientists Genetically Engineer Plants to Yield More Vegetable Oil

Published:01 Dec.2022 Source:Nanyang Technological University

Scientists from Nanyang Technological University, Singapore (NTU Singapore) have successfully genetically modified a plant protein that is responsible for oil accumulation in plant seeds and edible nuts.

Demonstrating their patent-pending method, the model plant Arabidopsis accumulated 15 to 18 per cent more oil in its seeds when it was grown with the modified protein under laboratory conditions.

Finding ways to make crops yield more oil in their seeds is a holy grail for the farming industry. However, most oil-producing crops -- such as oil palm, soybean, sunflower, rapeseed, peanut -- already have a high percentage of oil in their fruit or seed, and it is hard to increase their oil content through traditional crop crossbreeding methods.

Vegetable oils are commonly used in food processing, biofuels, soaps and perfumes, and the global market for them is estimated to be worth US$241.4 billion in 2021 and is expected to increase to US$ 324.1 billion by 2027[1]. Increasing the yield of oil from plants could also help the world in its quest for sustainability, helping to reduce the amount of arable land needed for oil-yielding crops.

The secret to helping plants store more oil in their seeds is one of their proteins called WRINKLED1 (WRI1). Scientists have known for over two decades that WRI1 plays an important role in controlling plant seed oil production.

Now for the first time, a high-resolution structure of WRI1 has been imaged and reported by the NTU team, jointly led by Associate Professor Gao Yonggui and Assistant Professor Ma Wei from the School of Biological Sciences.

Published in the scientific journal Science Advances, the team detailed the molecular structure of WRI1 and how it binds to plant DNA -- which signals to the plant how much oil to accumulate in its seeds.

Based on the understanding that the atomic structure of the WRI1-DNA complex revealed, the team modified WRI1 to enhance its affinity for DNA in a bid to improve oil yield. In this approach, some portions in WRI1 were selected for modifications to improve its binding to DNA and several forms of WRI1 were produced.

These candidate WRI1s were then further tested to assess their ability to activate oil production in plant cells. As expected by the team, they showed that their modified versions of WRI1 increased DNA binding ten-fold compared to the original WRI1 -- ultimately leading to more oil content in its seeds.

Assoc Prof Gao, a structural biologist said: "Being able to see exactly what WRI1 looks like and how it binds to DNA that is responsible for oil production in the plant was the key to understanding the entire process. WRI1 is an essential regulator that informs the plant how much oil to store in its seeds. Once we were able to visualise the 'lock', we then engineered the 'key' that can unlock the potential of WRI1."

Analysing at the atomic level, the crystal structure of the WRI1 protein and the double helix DNA strands to which it binds, the team noticed this DNA binding domain was extensively conserved. This means that there were little to no variations, suggesting it could be a common binding mechanism for many plant species.

Using this crystal structure of WRI1 as the 'target', the team then looked to modify WRI1, to enhance the binding affinity of the protein for its target DNA. The instructions for coding this modified WRI1 protein are then introduced into the target plant cells, after which the plant will use this new 'set of instructions' whenever it produces WRI1.

In lab experiments to observe how the modified WRI1 affects oil accumulation, both the modified protein and the unmodified form were injected into Nicotiana benthamiana leaves, and an analysis of triacylglycerol (a major form of dietary lipid in fats and oils) levels was carried out. The modified WRI1 protein generated more significant spikes in triacylglycerol production compared to the control plant introduced with the WRI1 unmodified form.

Subsequent experiments showed that the oil content in the seeds of the modified Arabidopsis thaliana contained more oil than the unmodified form. The offspring of this genetically modified plant will also bear the same modified WRI1 protein and produce more oil in their seeds.