Perspectives Online

CALS plant biologist studies the ‘remarkable nanomachine’ behind the structure of plant cellulose


Dr. Candace Haigler (center), shown here with colleagues Dr. Thanh-Tuyen Nguyen (right) and Dr. Rami Alkhatib, is among researchers partnering in the Center for Lignocellulose Structure and Formation, with a goal of improving methods for converting biomass into fuels.

Photos by Becky Kirkland

Dr. Candace Haigler, professor of crop science and plant biology in the College of Agriculture and Life Sciences, and two fellow N. C. State University faculty members are partnering with faculty from Penn State University and Virginia Tech in the new Center for Lignocellulose Structure and Formation (CLSF). The center was funded recently by the Department of Energy as an Energy Frontier Research Center. Haigler, Dr. Yaroslava Yingling, assistant professor of materials science and engineering, and Dr. Alex Smirnov, professor of chemistry, are N.C. State’s faculty research participants in the center, directed by Dr. Daniel Cosgrove, professor of biology at Penn State, the center’s lead institution. In addition, undergraduates, graduate students and advanced researchers will participate in the project.

Dr. Candace Haigler is shown with the Cressington CFE-60 freeze structure and etching system used in preparing plant cell samples before observation in a transmission electron microscope, equipment which enables delivery of three-dimensional, high-resolution views of cellular membranes and their associated proteins.
According to the CLSF Web site (www.cals.lignocellulose.org), lignocellulose is the major structural material of plant bodies and is the biorenewable resource that is used to make building materials, textiles and polymer derivatives. Answering questions about the structure and formation of lignocellulose is the work of the scientists in the center, with an overall objective is “to dramatically increase our fundamental knowledge of the physical structure of bio-polymers in plant cell walls to provide a basis for improved methods for converting biomass into fuels.”

The partnering universities will each focus on one of three themes of the center: 1) the physical process of cellulose microfibril formation in plant and microbial systems; 2) the structure and assembly of lignocellulose from its constituent components; and 3) the bridging of the knowledge from themes 1 and 2, about nano-scale structure and macro-scale properties, to real-world applications.

The CALS part of the center’s theme 1 research about cellulose synthesis and microfibril assembly takes place at Haigler’s lab in Williams Hall and at the Center for Electron Microscopy in Gardner Hall. Smirnov’s protein chemistry and nanobioengineering lab is nearby in Cox Hall, and Yingling’s computational modeling lab is in Engineering Building 1 on Centennial Campus.

Dr. Rami Alkhatib (left), Dr. Candace Haigler and Dr. Thanh-Tuyen Nguyen are exploring the protein structure and mechanisms of the cellulose synthesizing complex which modulates and regulates cellulose fibril formation from soluble sugar in a plant – and which Haigler describes as “one of the more remarkable nanomachines that exist in nature.”
The main objectives of the collaborative group are to reveal the protein structure and mechanisms of operation of the cellulose synthesizing complex (CSC), a protein-based nanomachine; and to perform computational modeling of the CSC and its operation to form cellulose nanofibrils.

Haigler calls CSC “one of the more remarkable nanomachines that exist in nature.” Essentially it modulates and regulates cellulose fibril formation from soluble sugar in a plant. “In plant cells, the CSC also moves in the membrane to orient cellulose fibrils and interacts with cytoskeletal elements,” she says. “At NCSU, we will undertake work to analyze cellulose synthase (CS) protein structure and define the structural and functional mechanism of CSC operation.”

The emphasis is on bioenergy applications, and findings could help in the improvement of cellulose-based biomaterials, such as wood pulp and cotton fiber.

Haigler, shown at work in Gardner Hall, calls plant cellulose “the most abundant renewable material that we have. It is important to sustainable human civilization and worldwide economies to know how to make the best use of these natural materials.”
“Biomaterials are used relatively intact within consumer products because they have useful inherent physical properties,” Haigler explains. “Lignocellulose biomass crops are grown in order to break down the original plant structure into sugar (e.g. for biofuel or use as animal feed). Both uses of plants – as biomaterials or biomass feed stocks – place a great deal of importance on the cellulose component of plant biomass.”

Cellulose-based products include biofuels and fuel for burning; chemical cellulose; timber, fiber, forage, pulp and manufactured wood products; animal feed, paper, textiles, sacking and boxing material; cordage; brushes and brooms; filling and stuffing; and caulking, filters and thickeners. Cotton fiber is the source for textiles and fillers, as well as chemical cellulose. 

“Cellulose within plants is the most abundant renewable material that we have,” says Haigler. “It is important to sustainable human civilization and worldwide economies to know how to make the best use of these natural materials. When we understand the mechanisms by which cellulose is made, we will have new insights into strategies for improving plants to support many industries that currently rely on cellulose-based plant products as well as devising new products that make use of novel cellulose properties.”

Alkhatib, Haigler and Nguyen are poised for a spectacular view of the cellular protein machine that manufactures cellulose fibrils in plants.
Because of the importance of cellulose in nature and to sustainable energy for human civilization, Haigler says it is surprising that we still have few details about the structure of CS or the CSC mechanistic operation.

“Our ability to devise strategies to improve the properties of cellulosic biomass and biomaterials is extremely limited,” she says. “Fully understanding the structure and function of this nanomachine is one of nature’s grand challenges and represents a major opportunity to add value to the future carbohydrate-based economy.”

To that end the N.C. State team is combining technical approaches, including high-resolution imaging of plant cells, nano-engineering of supported membrane bilayers, including CS protein fragments/protein; and computational modeling of CS and CSC structure.

 With a grant from the N. C. Biotechnology Center, Haigler’s team recently acquired a major piece of equipment for this endeavor. The Cressington CFE-60 freeze structure and etching system is a means of preparing plant cell samples before observation in a transmission electron microscope (TEM). “It provides a novel means of delivering three-dimensional, high-resolution views of cellular membranes and their associated proteins,” says Haigler. “In this project we will use it to visualize the cellular protein machine that manufactures cellulose fibrils. We will analyze the normal cellulose synthesizing complex and ones that have been disturbed through genetic changes or application of chemicals that inhibit cellulose synthesis.

“We will also be able to analyze the different types of proteins in the cellulose synthesizing complex. These experiments will lead to a better understanding of how the cell can organize and control a protein machine to spin soluble sugar into structural cellulose fibrils,” she says.


“This is undoubtedly one of the most fascinating processes carried out in nature.” – Terri Leith