Scientists at Wageningen University & Research have created a breakthrough method for plant regeneration that eliminates the need for hormones, using just two genes to trigger the process and potentially revolutionising crop breeding across multiple species
Researchers at Wageningen University & Research (WUR), working in close collaboration with KeyGene, have developed a method that enables plant cells to regenerate into complete plants without the need for added hormones.
This newly developed method, it said, can help plant breeders accelerate the development of innovative varieties across various crops.
The findings have been published in the scientific journal ‘The Plant Cell’.
Some plants can grow a root, a leaf or even an entire plant from a single plant cell.
“We call this process regeneration,” explained Jana Wittmer, cell biology researcher at WUR. “This works because a specific cell, such as a root or leaf cell, can be converted into an undifferentiated state – in other words, a stem cell.
”From this stem cell state, the cell can specialise all over again and develop into a root or leaf, or even into a completely new plant.
Maintaining plant varieties
“Regeneration is widely used in agriculture, for example in plant breeding,” said Wittmer. “Regeneration ensures that, when you create new plants, the genome of the original plant is passed on identically to the next generation.
”In this way, you can maintain the genetic make-up of a plant or plant variety over successive generations.
”Until now, breeders have used plant hormones in the regeneration process,” she outlined. ”They add these hormones to the growth medium in which the plant, or part of it, is placed.
”This often involves young plant tissues, because older, more differentiated tissues respond less well to hormone treatment.
”By adjusting the hormone regime – which controls plant development and growth – we can steer the development of stem cells so that they grow into roots or shoots, for example,” she pointed out.
Drawbacks of hormone treatment
“However, regeneration with the help of hormones also has its drawbacks and limitations,” Wittmer continued. ”The process is very labour-intensive and time-consuming.
”You first have to determine experimentally which treatment works best for the plant in question. Every plant species needs a different hormone regime, and even within a single species these regimes can vary.
”On top of that, for quite a few crops, such as pepper and cucumber, we currently still do not have a hormone regime that allows us to carry out the process in a reproducible way,” she said.
”Hormone-based regeneration does not always work, and even when it does, it takes a lot of time and effort - and that also means high costs.”
Alternative method
The researchers set out to find an alternative way to achieve regeneration without using hormones.
In doing so, they were inspired by a Nobel Prize-winning method that has been applied in animals, WUR stated.
“This technique is also known as induced pluripotent stem cells,” Wittmer confirmed. ”In plants, regeneration proceeds via a transient, or temporary, stage in which root stem cells are created.
”Our group has been working on root stem cells for many years, so we know the genes that are important for these stem cells.
”The next step is to test different combinations of these genes to see whether you can ‘reprogramme’ cells into a stem cell,” she said. ”From there, the cell can develop into any type of organ.”
Works across a wide range of plants
Through a series of experiments, the researchers succeeded in regenerating plants without adding hormones.
The most surprising outcome, according to Wittmer, was that they needed only two genes to trigger regeneration in the cells.
“After that, you do not have to intervene at all – the plant cells organise themselves,” she noted. ”From a block of cells, an entire plant develops again.
”We have demonstrated that this works in the model plant Arabidopsis, but also in crops such as tomato, lettuce and bell pepper.
”In principle, the technique can therefore be applied to a wide range of plant species, including species like bell pepper that do not respond to hormones, or for which we have not yet found a suitable hormone treatment,” Wittmer outlined.
“Eliminating the need for hormones in regeneration can save breeders a great deal of time and work. In addition, our method makes it easier to introduce or switch off genes, because that process also relies on regeneration.
”This could help make plants more resilient to diseases and pests, for example,” she said. ”In turn, that can have positive effects on crop yields and on the environment.”
Searching for a GMO-free approach
At the same time, Wittmer stressed that the study is only a first step in developing the technique.
“It is not yet ready to be used in practice,” she commented. ”In the lab we changed the plants’ genetic material. Bringing genetically modified plants to the market in Europe is a particularly costly and therefore hardly feasible route.
”We now need to find a way of activating the regeneration genes without using genetic modification.
”One option, for instance, would be to deliver the proteins into the cells that are encoded by the regeneration genes,” Wittmer suggested.
”If that proves possible, the method could be used immediately. But we first need to investigate and develop this further. That could easily take several years.”
Opening doors for follow-up research
For science, this induction system opens many doors, she said.
“We can now study the regeneration process in greater depth, and in a much simpler way.
”It also raises some fascinating follow-up questions. Why does regeneration work well in some cell types and plant species, but not in others, for example?” Wittmer pondered.
”It is also exciting to explore how we might maintain the stem cell stage. At present, we can activate genes that trigger stem cell formation, but these cells then regenerate directly into a plant.
”If you could maintain a stem cell, you could steer it towards a specific plant cell type – for instance, cells that produce particular pharmaceutical compounds or other valuable molecules,” she added. ”But that is work for the future.”
