Scientists Uncover Molecular Secrets of Vine Growth and Parasitic Behavior
Vines attach to other plants, blocking sunlight and impeding nutrient flow, which constitutes parasitic behavior. Previously, the specific mechanisms enabling vines to search, attach, and climb were not fully understood.
An international team of scientists has identified a formula for vine growth, which includes rapid elongation, directional movement, and the production of specialized contacting cells. The study also pinpointed the gene family responsible for engineering this formula.
Joyce Onyenedum, an assistant professor of environmental studies at New York University and a study author, stated that the research clarifies the link between molecular mechanisms and plant movement, providing insight into these parasitic plants which affect trees and other plants crucial for storing atmospheric carbon dioxide.
G-Fibers and Hormonal Control
Previous research established that large tree branches bend via G-fibers, specialized contracting fiber cells. A prior study by Onyenedum and colleagues found G-fibers in vine stems, though their specific role was unclear at the time.
The recent study, published in the journal New Phytologist, investigated this by examining common bean vines. Researchers studied the hormone brassinosteroid, known to regulate plant developmental processes including elongation. They compared normal bean vine growth to vines engineered to produce an excess amount of this hormone.
Vines with excess brassinosteroid exhibited repressed G-fiber development, leading to rapid, directionless elongation, termed 'lazy vines,' which hindered climbing.
Identifying Key Genes for Twining
Researchers also identified the candidate gene XTH5, which is essential for plants' structural growth and is specifically expressed during G-fiber development. This gene may be key to the coiling and gripping actions of vines.
Charles Anderson, a Penn State biologist and co-author, explained that genes like XTH5 enable plants to remodel their cell walls, which are vital for plant strength and flexibility. The study demonstrates cell wall remodeling as a critical component of plant movements such as twining.
Onyenedum concluded that rapid elongation, directional movement, and specific cell production facilitate vines' maneuvering and eventual attachment to hosts, revealing the mechanics of their behavior.
Additional researchers from the New York Botanical Garden, Brazil's Federal University of Rio Grande do Sul, and the University of Michigan contributed to the study. The National Science Foundation provided support through a CAREER Award.