¹³C Nuclear Magnetic Resonance Study of Suberized Potato Cell Wall

Abstract

High-resolution, solid-state 13C nuclear magnetic resonance (NMR) spectra are reported for suberized cell wall from potatoes (Solanum tuberosum L.). Through experiments combining the techniques of cross polarization and magic-angle spinning, we verified that suberin, like cutin, is a polyester and demonstrated that it also has phenylpropanoid groups characteristic of lignin. Roughly 50% of the suberized material consists of cell-wall polymers; aromatics and other unsaturated linkages outnumber methylene groups 2:1. In conjunction with traditional direct-polarization NMR results, these experiments provide support for prior suggestions that suberin and cell-wall components are chemically bonded via aromatic groups.Suberin and cutin are biopolymers with important protective functions in higher plants, serving as barriers against moisture loss for underground and aerial organs, respectively. For example, the formation of suberin within cell walls helps to prevent moisture loss and decay in potatoes, while the cuticular layer of fruits mitigates the effects of evaporation, wind, and fungal pathogens. Suberization also occurs as a defensive response, with polymer deposition occurring for approximately 1 week following wounding of the tissue. The ultrastructure, biosynthesis, and chemical identification of these materials have been the subject of much study during the past 20 years, with the goal of developing a molecular rationale for their physiological functions (5, 6).Spectroscopic analysis of intact cutin and suberin has been limited by their insolubility, and because the suberized cell wall forms an inseparable and chemically complex unit. Instead, research in this area has focused on characterization of the soluble, monomeric products of chemical depolymerization treatments. Using primarily GC-MS, both materials have been identified as polyesters. An incomplete picture of biopolymer structure emerges from such studies, however, since much of the plant material is resistant to degradation and the identification of monomeric constituents alone provides little clue as to how the units are linked together in living plants.A new spectroscopic approach to plant polyester structure ' (22). In the latter case, it was possible to determine the identity, number, and motional characteristics of the major carbon types and to develop a working model of cutin as a flexible netting with some cross-link constraints.In the current work, we present high-resolution naturalabundance '3C NMR results for suberized cell-wall tissue from wound-healing potatoes (18). CPMAS is employed to identify major chemical functionalities of both the suberin and cellwall components and to estimate the relative numbers of each carbon type present. These results allow compositional comparisons to be made with cutin, lignin, and the soluble depolymerization products of suberized potato tissue. In conjunction with traditional DPMAS, the CPMAS spectra are examined in light of proposed models for the attachment of suberin and polysaccharide co...

Suberin of Potato (Solanum tuberosum Var. Nikola): Comparison of the Effect of Cutinase CcCut1 with Chemical Depolymerization

“…The spectra of residue 1 ( Figure 4A (6,7,9,10). The signals at 170-180 ppm should arise from carbonyl resonances possibly present in aromatic structures and/or polysaccharides such as pectin or hemicellulose or, eventually, of suberin components.…”

“…Compounds having odd-numbered carbon chains have been identified from suberin monomers, but their amounts are smaller than those of similar even-numbered-chain compounds (16). Hydroxycinnamate-based polymers with some lignin-like components predominate in the polyphenolic domain of natural and wound-induced potato suberin, but differ from each other in composition (8,9,11,13).…”

“…This fraction has been studied mainly with spectroscopic methods, for example, FT-IR or solid state NMR (4,(6)(7)(8)(9)(10) or degrading methods, such as thioacidolysis (11). These analyses have shown this fraction to contain mostly substituted hydroxycinnamic acids, especially ferulic acid (2,(11)(12)(13) with relatively smaller amounts of phenylpropanoid-type structures, similar to lignin monomers (2,11).…”

Root-preferential mRNA accumulation in Zea mays

“…The Casparian strip is a band-like region of the primary cell wall that is impregnated with suberin. Suberin is a complex polymer composed of varying amounts of aliphatic and aromatic domains (Kolattukudy, 1987;Garbow et al, 1989). The aliphatic domains originate from fatty acids and are structurally similar to cutin.…”

“…The aliphatic domains originate from fatty acids and are structurally similar to cutin. The aromatic domains originate from phenylpropanoid precursors and are structurally similar to lignin (Kolattukudy, 1987;Garbow et al, 1989).…”