Scientists unravel vines’ parasitic nature

(Press-News.org) Twisting upwardly on trees and other plants—along with houses and even lampposts—vines are a wonder of nature. However, their marvels mask their parasitic behavior: in attaching to other life forms, vines block sunlight necessary for growth and strangle their hosts, preventing the flow of water and other nutrients.

While these threats were widely known, less clear is what gives vines their searching, attaching, and climbing capabilities. 

An international team of scientists has now unlocked a formula that enables vines to search for and attach to host plants—rapid elongation, directional movement, and the production of specialized contacting cells—and identified the gene family that engineers this formula. 

“Our research shows how molecular mechanisms are linked to plant movement—something we haven’t clearly understood,” explains Joyce Onyenedum, an assistant professor of environmental studies at New York University and an author of the study, which appears in the journal the New Phytologist. “Crucially, it gives us greater insight into these ropey parasites. They pose an ongoing menace to trees and other plants—among nature’s best tools for storing atmospheric carbon dioxide.”

It has been well-established that large tree branches bend through the production of fiber cells, called “G-fibers”, which are specialized cells that contract. In a study published last year, Onyenedum and her colleagues reported that G-fibers were common within the stems of vines. But the actual role of these cells was unclear.

In the New Phytologist study, Onyenedum and her colleagues, who included Lena Hunt, an NYU postdoctoral researcher, and Charles Anderson, a Penn State biologist, sought to address this question. 

To do so, the scientists studied common bean vines, which are cultivated globally, often seen in home gardens, and grow vertically. Specifically, they studied the role of a particular hormone, brassinosteroid, which is known to regulate plants’ developmental processes, including elongation, by comparing growth in a normal bean vine to one that was engineered to produce an excess amount of this hormone. 

These excess hormones repressed the development of G-fiber cells and produced “lazy vines” that elongate too fast and move in directionless manner.

This timelapse video shows the two bean vines—the left plant has hormone levels typically found in vines and climbs normally; the right plant, by contrast, has an excess amount of hormones, creating an imbalance that stifles climbing (video courtesy of the Onyenedum Lab/New York University).

The researchers also identified a candidate gene, XTH5, which is fundamental in plants’ structural growth and is specifically expressed during G-fiber development—thus potentially spotting the key actor supporting the coiling and gripping of vines.

“Genes like XTH5 allow plants to remodel their cell walls, which are complex structures that provide strength and flexibility to plants. This study demonstrates that cell wall remodeling is a critical component of plant movements such as twining,” says Anderson. 

“Our work shows that rapid elongation, directional movement, and the production of certain cells facilitates the maneuvering and eventual attachment of vines upon their host, thus unlocking the secrets to their behavior,” concludes Onyenedum. 

The study also included researchers from the New York Botanical Garden, Brazil’s Federal University of Rio Grande do Sul, and the University of Michigan.

This research was supported by an CAREER Award from the National Science Foundation (240167).

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