Study reveals how plants grow thicker, not just taller
Computer model provides insights in stem cells behind plant growth
image:
Prof. Kirsten ten Tusscher
view moreCredit: Utrecht University
Most research on plant stem cells focuses on the tips of roots and shoots, where growth occurs in height. But Ten Tusscher explains that thickness growth is just as essential. “Plants can’t grow endlessly in height. They also need to grow in thickness, or they would simply fall over,” she says. The growth in thickness, is what makes older trees visibly thicker and more robust over time. This growth is essential for structural strength, particularly in trees.
Stem cells in the plant’s cambium layer control this width growth, producing wood to support the plant’s structure. However, which genes enable these cambium stem cells to become active and how this is controlled remained unclear—until now.
Fundamental insights
Biologist Kirsten Ten Tusscher and her team developed a computer model that played a central role in this international study, which brought together scientists from Utrecht University and the University of Helsinki, Durham University, and the University of California. Her computer model provided fundamental insights, supporting lab results from the other team members as well as providing important predictions.
Computer model simulates wood formation
Ten Tusscher’s model explores how specific genes “switch on” cambium stem cells as the plant develops, allowing for wood formation. While genes for height growth have been studied before, this is the first model to examine genes that control thickness growth and what determines where these genes are switched on.
From the model’s output, Ten Tusscher’s team found that thickness growth is controlled by overlapping gradients of specific chemical signals within the cambium layer. These gradients intersect to form a precise zone where stem cells are “switched on,” guiding them to produce wood tissue. This interaction ensures that wood formation occurs steadily throughout the plant’s life, providing the structural strength and stability needed to support height growth.
Model plant
The computer model revolves around the small plant Arabidopsis, a species studied extensively by biologists worldwide to gain knowledge about plant growth in general. The model shows how cambium stem cells are activated and maintained, enabling continuous growth in thickness throughout a plant’s life.
Improving forestry and CO2 storage
Understanding thickness growth isn’t just a scientific milestone; it could lead to real-world applications in forestry and climate action. A deeper learning about plant growth is especially relevant for forestry, particularly in Finland, where forests play a major role in the economy, says Ten Tusscher.
“If you fully understand plant growth, and develop a tree that grows twice as fast in thickness, it’s a great benefit for more sustainable timber industry,” says Ten Tusscher. “It’s also advantageous for climate efforts, as faster-growing trees can store more CO₂. Perhaps, it could even help researchers tune thickness growth in crops for better agricultural yield.”
Journal
Science
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Identification of cambium stem cell factors and their positioning mechanism
Article Publication Date
7-Nov-2024
Defense or growth – How plants allocate resources
University of Helsinki
The more a plant species invests in defense, the less potential it has for growth, according to a new study. Research made possible by open science provides new insights into plant adaptation and interspecies variation.
Pathogens can significantly weaken the fitness of their hosts, sometimes even causing host mortality. Yet considerable variation is found between species in their investment in disease defense. Evolutionary theory predicts that allocation costs regulate this investment, but testing this hypothesis has been challenging.
In a study published in Science, postdoctoral researcher Michael Giolai and Professor of Plant Biodiversity Anna-Liisa Laine from the University of Helsinki used open databases to identify plant defense genes and growth traits in 184 plant species. They found striking variation among plant species in the number of defense genes, which ranged from 44 to 2,256. Examples include asparagus, which has only 72 resistance genes, while one chili variety has as many as 1,095. Laine and Giolai also discovered a negative correlation between defense investment and growth traits in wild plants: the higher that the proportion of a plants’ genome is dedicated to defense genes, the lower growth potential it has.
“Our study demonstrates the significant role of allocation costs in the generation and maintenance of biodiversity. The findings also shed light on mechanisms that limit the evolution of defense,” explains Michael Giolai.
Allocation costs refer to the trade-off in distributing resources among different life functions. For plants, this means that if a plant uses many resources (like energy and nutrients) to maintain its defenses, this may detract from other functions such as growth. In other words, the plant must balance its resource use, which can lead to a scenario where a strong defense reduces growth potential, or vice versa.
The study also examined cultivated plants that have been bred for specific traits. In these plants, a negative correlation between growth and defense was not observed due to the breeding that reduced natural variation in the genomes of crop plants.
Giolai and Laine’s research is an excellent example of the potential of open science. Sequencing the genomes of hundreds of plant species and collecting data on growth traits would be impossible for a single research team. The increase in open data enables new types of research that help us understand interspecies variation in different traits.
“If we want to understand the mechanisms that maintain interspecies trait variation, a multi-species approach like this is essential. The increasing availability of open data enables entirely new levels of investigation into these questions,” states Anna-Liisa Laine.
Journal
Science
Article Title
A trade-off between investment in molecular defence repertoires and growth in plants
Article Publication Date
8-Nov-2024
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