UC Davis collaborative study looks to poplars to understand trees’ growth-regulation process
By YASH RATHI — science@theaggie.org
The UC Davis College of Biological Sciences has started a new project that studies the function of the genes that regulate growth and wood formation in poplar trees. The U.S. Department of Energy (DOE) is funding the $2.5 million, three-year-long project that is to be led by Nitzan Shabek, an assistant professor in the UC Davis Department of Plant Biology, along with Andrew Groover of the USDA Pacific Southwest Research Station and Justin Walley of Iowa State University. The project is one of 37 being funded by the DOE in an effort to forward bioenergy technology.
Poplar trees have become of particular interest for bioenergy production because of their potential to be a solid biofuel source, as liquid fuel can be derived from poplars just two to five years after planting.
Their wood and growth formation are controlled by a set of complex proteins produced by various genes. The protein regulation inside a tree is balanced because of the ratio of proteins produced by gene regulation to the amount of protein that is removed by the cells through a “waste disposal” system called the “ubiquitin-proteasome system.” This regulation process specifically supports the trees during drought periods when the growth rate of the trees is highly affected. Their mortality rate increases, and this regulation helps the plant to grow and survive despite harsh conditions.
Shabek believes that this nuanced regulation system may be the key to using drought-resistant trees as a source of bioenergy.
“It is remarkable that plants amazingly adapted the ubiquitin system to tightly regulate networks of genes to cope with the ever-changing environment,” Shabek said. “We study this system at the molecular levels in the lab [by] integrating plant biology with advanced biochemistry and structural biology methods.”
Walley’s team is conducting work on biological regulatory pathways using the multi-omics approach, which studies multiple datasets of genes. Groover’s team has conducted detailed research that focused on the regulation of the diameter of water-conducting cells in poplar trees.
According to the paper, the team looked at growth and behavior of poplar stems in response to hormone treatment. They found that hormones directly regulate the trees’ stem growth and ability to bend due to gravity. Studying these hormone interactions and underlying mechanisms can help pave the way to optimize usage of poplar trees as a reliable bioenergy source.
“We manipulated hormone levels and response in poplar stems,” the paper reads. “Our main finding included hormone treatment that influences stem growth and xylem formation during secondary growth. It also affects tension wood formation in response to gravibending, the bending of woods due to gravity.”
Shabek said that his decision to use poplar trees for the study was in part because of their quick growth rate.
“In this project, we joined forces with world experts to better understand how growth and wood formation is regulated in trees and how the ubiquitin system involved in those complexities from genes function in challenging environments.” Shabek said. “We used model trees, poplars, that can grow relatively faster and therefore can be studied in several months at multiple levels.”
The main focus of this project is to understand the key component of this unique “waste disposal” system and how it regulates protein levels in the trees. Their final goal is to create a model that can infer the different processes for bioenergy applications and optimal biomass yield.
“Trees are critical foundations of life, as a source of food and oxygen with vast ecological and environmental values,” Shabek said. “As such, better understanding the molecular biology and biochemistry of tree growth are of utmost importance, especially on the verge of major global climate change. The long-term goals are to develop models that could predict processes for better biomass yield and bioenergy applications.”
Written by: Yash Rathi — science@theaggie.org
