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Cell wall composition determines handedness reversal in helicoidal cellulose architectures of Pollia condensata fruits.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Middleton, Rox 
Ogawa, Yu 
Gregory, Tom 
Steiner, Lisa M 

Abstract

Chiral asymmetry is important in a wide variety of disciplines and occurs across length scales. While several natural chiral biomolecules exist only with single handedness, they can produce complex hierarchical structures with opposite chiralities. Understanding how the handedness is transferred from molecular to the macroscopic scales is far from trivial. An intriguing example is the transfer of the handedness of helicoidal organizations of cellulose microfibrils in plant cell walls. These cellulose helicoids produce structural colors if their dimension is comparable to the wavelength of visible light. All previously reported examples of a helicoidal structure in plants are left-handed except, remarkably, in the Pollia condensata fruit; both left- and right-handed helicoidal cell walls are found in neighboring cells of the same tissue. By simultaneously studying optical and mechanical responses of cells with different handednesses, we propose that the chirality of helicoids results from differences in cell wall composition. In detail, here we showed statistical substantiation of three different observations: 1) light reflected from right-handed cells is red shifted compared to light reflected from left-handed cells, 2) right-handed cells occur more rarely than left-handed ones, and 3) right-handed cells are located mainly in regions corresponding to interlocular divisions. Finally, 4) right-handed cells have an average lower elastic modulus compared to left-handed cells of the same color. Our findings, combined with mechanical simulation, suggest that the different chiralities of helicoids in the cell wall may result from different chemical composition, which strengthens previous hypotheses that hemicellulose might mediate the rotations of cellulose microfibrils.

Description

Keywords

cellulose–hemicellulose interaction, chirality, helicoidal cell wall, mechanical properties of plant cell wall, structural colors

Journal Title

Proceedings of the National Academy of Sciences of USA

Conference Name

Journal ISSN

0027-8424
1091-6490

Volume Title

118

Publisher

National Academy of Sciences
Sponsorship
Biotechnology and Biological Sciences Research Council (BB/K014617/1)
European Research Council (639088)
Engineering and Physical Sciences Research Council (EP/G037221/1)
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