Project: Research project

Project Details


Principal Investigator: Daniel J. Cosgrove, Department of BiologyDOE/Office of Science Program Office: BES Physical BiosciencesPlants 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.Expansins – especially α-expansins - are key mediators of this process, but their novel physical effects on cell walls are not understood at the molecular level. In the work proposed here the PI will address this question by testing the structure-function relations of α-expansins, which are the most potent of the different classes of expansins. The recalcitrance of plant expansins to heterologous expression and the difficult physical properties of α-expansins in vitro have blocked progress towards this goal. Attempts at heterologous expression of plant expansins are being set aside in favor of an entirely different approach, based on computational modeling of an α-expansin from Arabidopsis, AtEXPA4. The model has already generated novel molecular insights into the control and actions of EXPAs. The predictions of the model will be tested by genetic complementation of an Arabidopsis line that is defective in the EXPA genes required for root hair elongation. The AtEXPA4 model enables the PI to identify residues potentially involved in pH and redox control of expansin protein dynamics and interactions with cellulose. These ideas will be tested by introducing mutated versions of AtEXPA4 in the Arabidopsis line lacking root-hair-specific expansins required for root hair elongation, to test for alterations in activity, pH sensitivity and redox sensitivity of the introduced protein. The root-hair defective Arabidopsis line was developed previously as a platform for testing the functionality of wild type and mutant EXPA genes. An additional subproject is a screen of an expression library of 200 highly diverse microbial expansin genes for novel activities (binding targets, biophysical and biochemical actions). This exploratory work is based on the hypothesis that the large diversity in microbial sequences reflects a large diversity of functionalities (substrates, physical actions, environmental optima) that evolved in the microbial world. The work is enabled by synthesis of the 200 constructs by DOE-JGI.In short, the proposed work will enable the PI to test molecular-level concepts about the mechanism and regulation of α-expansin activity and to explore microbial expansins for novel, perhaps useful and insightful, activities by these enigmatic proteins. If successful, the outcome will be deeper insights into the molecular basis of wall loosening, which is the key control of cell wall enlargement and limits accumulation of stored carbon and energy by plants.
Effective start/end date8/1/217/31/24


  • Basic Energy Sciences


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