Solid-State <sup>13</sup>C NMR Delineates the Architectural
Design of Biopolymers in Native and Genetically Altered Tomato Fruit
Cuticles
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Abstract
Plant
cuticles on outer fruit and leaf surfaces are natural macromolecular
composites of waxes and polyesters that ensure mechanical integrity
and mitigate environmental challenges. They also provide renewable
raw materials for cosmetics, packaging, and coatings. To delineate
the structural framework and flexibility underlying the versatile
functions of cutin biopolymers associated with polysaccharide-rich
cell-wall matrices, solid-state NMR spectra and spin relaxation times
were measured in a tomato fruit model system, including different
developmental stages and surface phenotypes. The hydrophilic–hydrophobic
balance of the cutin ensures compatibility with the underlying polysaccharide
cell walls; the hydroxy fatty acid structures of outer epidermal cutin
also support deposition of hydrophobic waxes and aromatic moieties
while promoting the formation of cell-wall cross-links that rigidify
and strengthen the cuticle composite during fruit development. Fruit
cutin-deficient tomato mutants with compromised microbial resistance
exhibit less efficient local and collective biopolymer motions, stiffening
their cuticular surfaces and increasing their susceptibility to fracture