Public Abstract

DE-FG02-84ER13179: MOLECULAR MECHANISMS OF PLANT CELL WALL LOOSENING

Award Status: Active

Institution: The Pennsylvania State University, University Park, PA
UEI: NPM2J7MSCF61
DUNS: 003403953

Most Recent Award Date: 09/23/2025
Number of Support Periods: 36
PM: Brown, Katherine

Current Budget Period: 08/01/2025 - 07/31/2026
Current Project Period: 08/01/2025 - 07/31/2026
PI: Cosgrove, Daniel

Supplement Budget Period: N/A

Public Abstract

Project Title: Molecular Mechanisms of Plant Cell Wall Loosening; Award #: DE-FG02-84ER13179 Applicant: Pennsylvania State University, Office of Sponsored Programs, 110 Technology Center, University Park, PA 16802 Principal Investigator: Daniel J. Cosgrove, Department of Biology DOE/Office of Science Program Office: BES Physical Biosciences Plants have the astonishing ability to expand a photosynthetic canopy to collect sunlight and atmospheric CO₂ and package the harvested energy and carbon into cell walls, a large-scale renewable source of bioenergy and biomaterials. These processes depend on the ability of the cell wall to grow in surface area. This project builds on recent discoveries about the actions of expansin proteins, which enable plant cell walls to enlarge irreversibly. The enigmatic wall loosening action by expansins underlies the remarkable ability of plants to expand a photosynthetic canopy to collect sunlight and atmospheric CO₂ and package the harvested energy and carbon into cell walls, a large-scale renewable source of bioenergy and biomaterials. In this one-year extension of our current project, we will narrow our focus to two questions. (A) What is the molecular mechanism of action of cell wall disruption by a diverse group of six microbial expansins? Microbial expansins will be expressed in E. coli; this is not feasible for plant expansins, so we make use of expression and complementation strategies in Arabidopsis thaliana for work with plant expansins. (B) Do ancient α-expansin (EXPA) clades possess novel and conserved functional differences from canonical α-expansins? For question A we will use: (1) mechanical assays to characterize the physical effects of the selected microbial expansins on wall elasticity, plasticity and breaking strength; (2) enzyme assays with defined substrates to identify their potential lytic activities against wall polysaccharides; (3) biochemical analyses to identify polysaccharides released from plant cell walls by expansin treatment; and (4) nanoscale imaging of wall surfaces treated with these expansins for clues about their mode of action. For question B we will use genetic complementation of a novel root-hairless expa7/expa18 double mutant line of Arabidopsis thaliana that we have recently developed, to test for cladal differences in complementation phenotypes, e.g. as observed for selected Arabidopsis EXPA genes (e.g. AtEXPA13 and AtEXPA20). The complementation phenotypes to be scored include function (restoration of root hair growth in the root-hairless expa7/expa18 double mutant), localization of chimeric EXPA-mCherry to the root hair initiation site, and stable binding of EXPA-mCherry to cell walls at the initiation site. To asses the alternative function and activities of the noncanonical EXPA13 and EXPA20, we will assess patterns of gene expression and protein localization and phenotypes of expa13 and expa20 mutants. Understanding expansin action is important for fundamental understanding of what limits the energy-gathering and carbon-storing potential of plants and for knowledge-based efforts to re-engineer crops for improvements in bioenergy and biomaterials. This work is relevant to the Physical Biosciences program which supports research into “the biochemical and biophysical principles determining the architecture of biopolymers and the plant cell wall.”

Project Title: Molecular Mechanisms of Plant Cell Wall Loosening;

Award #: DE-FG02-84ER13179

Applicant: Pennsylvania State University, Office of Sponsored Programs, 110 Technology Center, University Park, PA 16802

Principal Investigator: Daniel J. Cosgrove, Department of Biology

DOE/Office of Science Program Office: BES Physical Biosciences

Plants have the astonishing ability to expand a photosynthetic canopy to collect sunlight and atmospheric CO₂ and package the harvested energy and carbon into cell walls, a large-scale renewable source of bioenergy and biomaterials. These processes depend on the ability of the cell wall to grow in surface area.

This project builds on recent discoveries about the actions of expansin proteins, which enable plant cell walls to enlarge irreversibly. The enigmatic wall loosening action by expansins underlies the remarkable ability of plants to expand a photosynthetic canopy to collect sunlight and atmospheric CO₂ and package the harvested energy and carbon into cell walls, a large-scale renewable source of bioenergy and biomaterials. In this one-year extension of our current project, we will narrow our focus to two questions. (A) What is the molecular mechanism of action of cell wall disruption by a diverse group of six microbial expansins? Microbial expansins will be expressed in E. coli; this is not feasible for plant expansins, so we make use of expression and complementation strategies in Arabidopsis thaliana for work with plant expansins. (B) Do ancient α-expansin (EXPA) clades possess novel and conserved functional differences from canonical α-expansins?

For question A we will use: (1) mechanical assays to characterize the physical effects of the selected microbial expansins on wall elasticity, plasticity and breaking strength; (2) enzyme assays with defined substrates to identify their potential lytic activities against wall polysaccharides; (3) biochemical analyses to identify polysaccharides released from plant cell walls by expansin treatment; and (4) nanoscale imaging of wall surfaces treated with these expansins for clues about their mode of action.

For question B we will use genetic complementation of a novel root-hairless expa7/expa18 double mutant line of Arabidopsis thaliana that we have recently developed, to test for cladal differences in complementation phenotypes, e.g. as observed for selected Arabidopsis EXPA genes (e.g. AtEXPA13 and AtEXPA20). The complementation phenotypes to be scored include function (restoration of root hair growth in the root-hairless expa7/expa18 double mutant), localization of chimeric EXPA-mCherry to the root hair initiation site, and stable binding of EXPA-mCherry to cell walls at the initiation site. To asses the alternative function and activities of the noncanonical EXPA13 and EXPA20, we will assess patterns of gene expression and protein localization and phenotypes of expa13 and expa20 mutants.

Understanding expansin action is important for fundamental understanding of what limits the energy-gathering and carbon-storing potential of plants and for knowledge-based efforts to re-engineer crops for improvements in bioenergy and biomaterials. This work is relevant to the Physical Biosciences program which supports research into “the biochemical and biophysical principles determining the architecture of biopolymers and the plant cell wall.”