Scientist Discovered A Whole New Organ On 'World’s Best-Studied' Plant After Years Of Research

A common lab plant that has been poked and scrutinized for decades may appear unlikely to keep secrets. However, in the widely studied Arabidopsis thaliana, scientists have discovered the “cantil” — a newly discovered plant organ named for its cantilever-like structure — reaches out horizontally from the stem and supports the pedicel, a stalk that grows vertically and is topped off by a flower.

Plant biologists recently reported in the journal Development that the much-studied model plant Arabidopsis thaliana possesses an organ that researchers and naturalists had overlooked for centuries.

Arabidopsis thaliana, also known as the thale cress, has been the primary plant model for scientific research for decades, appearing in literally tens of thousands of papers. The small, weedlike plant's relatively simple genome and short lifecycle make it an ideal subject for genetic manipulation and experimentation.

Timothy Gookin, a molecular biologist at Pennsylvania State University, first suspected contamination or a mutation when he noticed some Arabidopsis thaliana with strange stalks jutting out from the stem, like half-finished bridges. 

“It took over 12 years of experimentation to really get a grasp on what we were seeing and to understand how cantils were regulated. This study required the growth of 3,782 plants to full maturity and the manual inspection of over 20,000 flower-bearing stalks in 34 unique plant lines,” Gookin said.

The appearance of a newly described cantilever-like organ is dependent on genetics and circumstance. It appears only in some Arabidopsis thaliana varieties and only when flowering is delayed, Gookin said.

It may sound odd that an organ could go undiscovered for so long, but this is because cantils only grow under certain conditions and at a particular time – during flowering when the days are short.

The authors show that cantils form only under certain conditions, most notably when daylight hours are short. Plants typically transition from shoring up resources to producing flowers as the seasons change from spring to summer. 

According to Gookin, Cantils form only when the thale cress postpones flowering, usually in the spring when daylight is limited. Compared to the sunny summer, the thale cress transitions more slowly from the leaf-production phase to the reproductive flowering stage during this season. At this slowed rate, the cantil emerges just as the flower-tipped pedicel emerges. Cantil will never appear if the plant only experiences seasons with long hours of sunlight. The thale cress is frequently grown under long daylight conditions.

Thale cress cantils give the plant the appearance of bent elbows; plants without cantils appear to have straight arms. Cantils do not belong to the stem or the pedicel. According to Gookin, they are an entirely new organ.

His subsequent research identified several genes involved in cantil formation, but the function of cantils is unknown.

François Parcy, a plant biologist at CNRS in Paris who was not involved in the study, tells Science News, “If you told me of a new organ in a weird plant in Amazonia, I wouldn’t be surprised at all,” “What struck me is this happened in Arabidopsis. This is something that’s really surprising.”

While it’s unclear now whether cantils help the thale cress survive in the wild or if the appendages are a harmless side effect of other changes within the plant, the structures could be vestigial, which means they are evolutionary leftovers from an ancient ancestor in the plant's lineage that no longer serve a practical purpose.

However, researchers believe that the discovery of cantils provides important clues for understanding the conditional growth of plant structures in response to their environment.