Now, scientists can make spinach leaves look like lettuce or coriander leaves

In a breakthrough genetic study, scientists were able to completely reshape leaves in trees and plants, and even increase their biomass. Besides providing insights into plant development, the findings could initiate innovations in the food industry.

The study, conducted by scientists at the Indian Institute of Science (IISc) and Shodhaka Life Sciences, Bengaluru, was published in the journal Nature Plants.

“One could use this technique to alter the shape of the salad leaves as one chooses, or increase their biomass,” said Krishna Reddy Challa, a former PhD student at IISc’s Department of Microbiology and Cell Biology (MCB) and co-lead author of the study.

Associate Professor Utpal Nath of MCB and senior author of the paper said that the application of the research clears the way to change the shape of a spinach leaf to look like lettuce or coriander, for example. “However, the true value of the research is that we have discovered some basic and elemental facts about how leaves grow,” he added.

Leaf types

Plants have either simple leaves or compound leaves. A mango tree, for example, possesses simple leaves because they have a single, intact leaf blade. However, a Gulmohar tree has compound leaves where the leaf blade is dissected into multiple leaflets.

Both simple and compound leaves start out as rod-like structures budding out from the meristem, the tip of the stem where stem cells are present. How these rod-like structures give rise to simple or compound leaves has been a subject of much investigation in the past years.

The scientists discovered that two gene families, CIN-TCP and KNOX-II, play a role in how leaves shape up. Their test subject was a plant called Arabidopsis thaliana – a popular model organism in plant biology.

The two gene families encode protein transcription factors that suppress the formation of new leaflets at the margin, thereby giving rise to simple leaves. When the researchers simultaneously suppressed multiple members of the two gene families, this caused simple leaves to become super-compound leaves. Suppressing the two gene families independently did not trigger a change. IISc scientists said that this suggests “that the genes work in concert.”

Also, while scientists have been previously able to convert compound leaves to simple leaves by manipulating the expression of certain genes, Professor Nath said their work is the first to go the other way around. “One of the key findings is that we can cause leaves to grow and grow without a set limit, much like mathematical fractals which can constantly multiply. It is an exciting discovery,” he said.

In addition, he pointed out that the mutant leaves were found to stay younger and grow for as long as they had the necessary growing conditions.

While Arabidopsis leaves typically mature in around 30 days and wither by 60 days, the leaves of these mutant plants grew for as long as the researchers followed them (175 days) – and could potentially go on for months or years given the necessary conditions.

The researchers found that the leaves of the plants in which the two gene families were suppressed, in contrast to normal Arabidopsis leaves, displayed RNA signatures of young immature leaves and actively dividing cells even beyond their typical maturation period. RNA is a chemical messenger which carries instructions from the genes required to synthesise proteins.

“Since the leaves don’t mature once the genes are suppressed, you can control the longevity of the plant and thereby extend its shelf-life,” added Monalisha Rath, a PhD student at MCB and co-lead author of the study.

Addressing food shortage

The breakthrough means that agriculturists growing leafy crops can increase their yields. However, Associate Professor Nath pointed out that there are always tradeoffs, in that the plants could take longer to grow. “In the case of our Arabidopsis test subject, flowering took much longer because it became delayed. In other studies, an attempt to increase the size of rice grains resulted in a fewer number of grains,” he said.