Zandraket (Arabidopsis thaliana)

Because of its simple genetics, Arabidopsis thaliana is cultivated in laboratories for use in research around the world. However, a new study shows it may be more exceptional than previously believed.

Arabidopsis thaliana grows abundantly in cracks in pavements all over Europe and Asia, but the small white flower leads a second life as the 'lab rat' of the plant world.

Now scientists believe one of the most fundamental processes in the life of plants has been misunderstood—because they have been looking at the wrong flower.

A new study published in The Plant Journal finds that Arabidopsis thaliana is exceptional in not having a key “censorship” protein called SMG1.

SMG1 plays a vital role in the growth of animals as multicellular organisms, but scientists thought that plants built their complex life in a fundamentally different way. That conclusion, it turns out, was built on a bit of subterfuge from Arabidopsis thaliana.

“Everybody thought that this protein was only in animals,” says Brendan Davies, professor of biology at the University of Leeds. “They thought that because, basically, most of the world studies one plant: Arabidopsis thaliana.”

Gene expression—the process by which the information from a genome is converted into the differentiated cells that make up complex life—relies on processes that turn genes on, when their genetic messages are required, and off when they are not.

 “Switching genes on and off is really what life is about. If you can’t do that, you can’t have life,” Davies says. “There are various ways this is done, but one way in more complex life such as animals and plants is through a sort of ‘censorship’ process.

“The system looks at the messages that come out of the nucleus and effectively makes a judgement on them. It says ‘I am going to destroy that message now’ and intervenes to destroy it before it takes effect.”

Scientists know that this “censorship” process—called Nonsense Mediated mRNA Decay (NMD)—is used by both plants and animals, but thought the two types of organism did it in different ways.

Because Arabidopsis thaliana does not have SMG1, which plays a key role in triggering the censorship system in animals, scientists had concluded that SMG1 was not present in any plant.

But researchers discovered the plant is in fact an anomaly.

“We have found that SMG1 is in every plant for which we have the genome apart from Arabidopsis and we have established that it is being used in NMD. Rather than being just in animals, we are suggesting that the last common ancestor of animals and plants had SMG1,” Davies says.

The study also found SMG1 in Arabidopsis lyrata, a close relative of Arabidopsis thaliana, which suggests that the missing protein has been lost relatively recently in evolutionary time, perhaps in the last 5-10 million years.

The next key question for researchers is to explain how organisms without SMG1, such has fungi and Arabidopsis thaliana, work without the protein.

Arabidopsis thaliana “is still a fantastically useful model,” Davies says. “We would not be anywhere close to where we are in understanding plant biology without it.

“But this is a lesson to us all about the dangers of extrapolating from a single model, however successful that model has been, and the importance of studying processes in a range of models. Evolution does strange and unpredictable things.”