Contributions of the mechanical properties of major structural polysaccharides to the stiffness of a cell wall network model.
OBJECTIVE
The molecular mechanisms regulating the expansive growth of the plant cell wall have yet to be fully understood. The recent development of a computational cell wall model allows quantitative examinations of hypothesized cell wall loosening mechanisms.


METHODS
Computational cell wall network (CWN) models were generated using cellulose microfibrils (CMFs), hemicelluloses (HCs), and their interactions (CMF-HC). For each component, a range of stiffness values, representing various situations hypothesized as potential cell-wall-loosening mechanisms, were used in the calculation of the overall stiffness of the computational CWN model. Thus, a critical mechanism of the loosening of the primary cell wall was investigated using a computational approach by modeling the molecular structure.


RESULTS
The increase in the stiffness equivalent of the CMF-HC interaction results in an increase in the Young's modulus of the CWN. In the major growth direction, the CWN stiffness is most sensitive to the CMF-HC interaction (75%). HC stiffness contributes moderately (24%) to the change in the CWN stiffness, whereas the CMF contribution is marginal (1%). Minor growth direction exhibited a similar trend except that the contributions of CMFs and HCs are higher than for the major growth direction.


CONCLUSIONS
The stiffness of the CMF-HC interaction is the most critical mechanical component in altering stiffness of the CWN model, which supports the hypothesized mechanism of expansin's role in efficient loosening of the plant cell wall by disrupting HC binding to CMFs. The comparison to experiments suggests additional load-bearing mechanisms in CMF-HC interactions.
The Department of the Agricultural and Biological Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 USA.
Hojae
H
Yi
Virendra M
VM
Puri
D002473:Cell Wall / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism*; D055119:Elastic Modulus; D020894:Microfibrils / Q000378:metabolism*; D008954:Models, Biological; D059828:Plant Cells / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism*
D011134:Polysaccharides; C007916:hemicellulose; D002482:Cellulose
cell wall loosening; cell wall mechanics; cellulose-hemicellulose interactions; computational cell wall network model; primary cell wall