Shared Roots: A New Molecule, Disease and Growth

For decades, the consensus in the scientific community has been that animals and plants split into different kingdoms over 1.3 billion years ago. So it makes sense that new research suggesting that plants and animals share a critical, previously uncharacterized enzyme called VAS1 is causing a bit of a stir.

Joanne Chory, a professor at the Salk Institute, has found that levels of two of the most important hormones that regulate growth in plants — auxin and ethylene — are finely regulated by VAS1. Auxin promotes growth, and ethylene (best known for ripening bananas) promotes aging and death. In living plants, the ratio of auxin to ethylene is determined by how much light a plant is getting. More light means more auxin, which means more growth — scientists have known this for decades. Put a plant in shade, and ethylene takes over, putting the brakes on growth.

What scientists didn’t fully understand, however, was how levels of these two hormones are regulated in plants. They had identified a pathway before, but it was slow and clunky, involving lots of enzymes and intermediate steps. If plants used that pathway alone, it would take them days to adjust to changing light conditions. This failure to adapt isn’t observed in nature — otherwise plants would be dying left and right.

Thus, many scientists have suspected that there had to be another, nimbler mechanism for modulating levels of ethylene and auxin. They were in the minority, however, until this month. That’s when it all changed.

“When we first tried publishing this paper based on this discovery, people in the scientific community were saying, ‘Well, we don’t understand why you need that enzyme,’” Chory said with a laugh.

This is where the VAS1 enzyme comes into play: VAS1 provides a shortcut to the slow and clunky pathway. In plants, this means quicker regulation of auxin and ethylene levels, which means a better adaptation to changing light conditions.

Interestingly, Chory found that this key regulator of plant growth, VAS1, has a close human analogue that had already been identified. It’s been implicated in several diseases that affect hundreds of millions of patients around the world — diabetes and arthritis are two of the biggest. Chory said she hopes that by better characterizing this pathway, the mechanisms underlying diseases like diabetes and arthritis can be better understood by researchers.

Chory collaborated with Joseph Noel, a chemist at the Salk Institute and director at the Skirball Center for Chemical Biology and Proteomics, so that she and the post-doctorates, working under her, Yongxia Guo and Zuyu Zheng, have a better understanding of the chemical reactions taking place in the mustard plants.

“Joe and his team make working on enzymes more fun,” Chory said. “In fact, it’s a nice give and take between the two labs, because we have a common interest, but we’re looking at different parts of the research.”

According to Chory, upon the discovery of the VAS1 enzyme, Noel suffered a few sleepless nights in order to form a sensible hypothesis.

Chory explained that this discovery of the VAS1 enzyme is truly a single chapter in the long history of studying plant growth and its relationship to human beings.

“In 20 years, we have learned how a plant adapts to shade, how one important hormone got made and identified an enzyme that people didn’t even know existed,” Chory said.

Moreover, Chory said that her experience with skeptics in the scientific community have taught her the value of thinking outside the box.

“Part of our message is to stay open-minded about what the mechanisms are going to be that link this small molecule to another small molecule,” Chory said. “It’s to keep your eyes open.”