Scientists probe mystery of phototropism while training young researchers

LAWRENCE — Plunk a houseplant near a window, and often that plant will bend eagerly toward the light to soak up as much energy as possible. Phototropism is the name of this process, and you can see it in organisms ranging from algae to sunflowers.

A protein cranked out by plant cells dubbed “phototropin” is key to this action. But how does this protein manage the growth of a plant toward sunlight?

“That’s what we’re trying to figure out,” said Carey Johnson, chemistry professor at the University of Kansas. “Phototropin has in it two domains called LOV domains. It’s the LOV domain that absorbs light — specifically blue light. Somehow a signal is relayed to the rest of the protein and then onto other parts of the plant. And it’s not really understood how that signal is relayed.”

Funded by a new $426,000 grant from the National Science Foundation, Johnson is leading a new international effort to better grasp how LOV domains communicate these signals. His goal is not just to advance human knowledge about phototropism, but also to train a new generation of scientists and science teachers to engage in research and international cooperation.

“We extract the protein from algae or we can synthesize the protein,” said Johnson. “Phototropism involves a change in the confirmation of the protein phototropin where the light triggers a chemical reaction within the LOV domain. But then somehow the information about that chemical reaction is transmitted though the protein or to other proteins. We want to see how this works using florescent spectroscopy, which is the interaction of molecules with light and then their reemission of light.”

Johnson and his team will attach a fluorescent dye molecule to amino acids associated with LOV domains and then use laser beams and light sensors to track the interactions of those molecules.

“The most challenging part will be to interpret what the signals that we see mean in terms of how the protein works,” said the KU researcher. “That’s often the hardest part to understand — what the signals are telling us. Then we’ll design a subsequent experiment to see if we got it right or not.”

Undergraduate and graduate students, whose lab training represents a chief objective of the NSF grant, will help collect and interpret the data. Additionally, the research effort will include undergraduates in the UKanTeach program at KU, which aims to counteract the shortage of high school math and science teachers in Kansas.

“They’ll learn by doing research with experienced researchers — it’s like an apprenticeship,” Johnson said. “They will be working with more experienced researchers and professors in the lab.”

Johnson and his collaborators and students also will join efforts with professor Bernhard Dick at the University of Regensburg in Germany, who is a longtime researcher of phototropism. The partnership will harness the expertise of both researchers and also facilitate international exchanges for the students involved in the project, so that they can learn state-of-the-art techniques from each laboratory.

“Science these days is really international and interdisciplinary, and so we think it’s important for students to experience both these aspects, and to learn methods that are used in more than one lab,” said Johnson. “Our lab has certain techniques that we’re experts at and Professor Dick’s lab has other techniques that his lab is expert at. So this will expose students more broadly to a range of techniques and methods that they can use in research.”