Sporopollenin is a ubiquitous and extremely chemically inert biopolymer that constitutes the outer wall of all land-plant spores and pollen grains1. Sporopollenin protects the vulnerable plant gametes against a wide range of environmental assaults, and is considered a prerequisite for the migration of early plants onto land2. Despite its importance, the chemical structure of plant sporopollenin has remained elusive1. Using a newly developed thioacidolysis degradative method together with state-of-the-art solid-state NMR techniques, we determined the detailed molecular structure of pine sporopollenin. We show that pine sporopollenin is primarily composed of aliphatic-polyketide-derived polyvinyl alcohol units and 7-O-p-coumaroylated C16 aliphatic units, crosslinked through a distinctive dioxane moiety featuring an acetal. Naringenin was also identified as a minor component of pine sporopollenin. This discovery answers the long-standing question about the chemical make-up of plant sporopollenin, laying the foundation for future investigations of sporopollenin biosynthesis and for the design of new biomimetic polymers with desirable inert properties.
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The data that support the findings of this study are available from the corresponding author upon request.
Kim, S. S. & Douglas, C. J. Sporopollenin monomer biosynthesis in Arabidopsis. J. Plant Biol. 56, 1–6 (2013).
Weng, J.-K., Philippe, R. N. & Noel, J. P. The rise of chemodiversity in plants. Science 336, 1667–1670 (2012).
Mansfield, S. D., Kim, H., Lu, F. & Ralph, J. Whole plant cell wall characterization using solution-state 2D NMR. Nat. Protoc. 7, 1579–1589 (2012).
Ahlers, F., Thom, I., Lambert, J., Kuckuk, R. & Wiermann, R. 1H NMR analysis of sporopollenin from Typha angustifolia. Phytochem. 50, 1095–1098 (1999).
Rolando, C., Monties, B. & Lapierre, C. in Methods in Lignin Chemistry (eds Lin, S. Y. & Carlton, W.) 334–349 (Springer, Berlin, 1992).
Seco, J. M., Quiñoá, E. & Riguera, R. The assignment of absolute configuration by NMR. Chem. Rev. 104, 17–118 (2004).
Imaizumi, K., Terasima, H., Akasaka, K. & Ohrui, H. Highly potent chiral labeling reagents for the discrimination of chiral alcohols. Anal. Sci. 19, 1243–1249 (2003).
Ohrui, H. Development of highly potent chiral discrimination methods that solve the problems of diastereomer method. Anal. Sci. 24, 31–38 (2008).
Ohtaki, T., Akasaka, K., Kabuto, C. & Ohrui, H. Chiral discrimination of secondary alcohols by both 1H-NMR and HPLC after labeling with a chiral derivatization reagent, 2-(2, 3-anthracenedicarboximide) cyclohexane carboxylic acid. Chirality 17, 171–176 (2005).
Zhang, Y.-J., Dayoub, W., Chen, G.-R. & Lemaire, M. Environmentally benign metal triflate-catalyzed reductive cleavage of the C–O bond of acetals to ethers. Green Chem. 13, 2737–2742 (2011).
Zhang, Y. J., Dayoub, W. & Chen, G. R. TMDS as a dual-purpose reductant in the regioselective ring cleavage of hexopyranosyl acetals to ethers. Eur. J. Org. Chem. 10, 1960–1966 (2012).
Dick-Pérez, M. et al. Structure and interactions of plant cell-wall polysaccharides by two- and three-dimensional magic-angle-spinning solid-state NMR. Biochemistry 50, 989–1000 (2011).
Wang, T., Phyo, P. & Hong, M. Multidimensional solid-state NMR spectroscopy of plant cell walls. Solid State Nucl. Magn. Reson. 78, 56–63 (2016).
Phyo, P., Wang, T., Yang, Y., O’Neill, H. & Hong, M. Direct determination of hydroxymethyl conformations of plant cell wall cellulose using 1H polarization transfer solid-state NMR. Biomacromolecules 19, 1485–1497 (2018).
Phyo, P. et al. Gradients in wall mechanics and polysaccharides along growing inflorescence stems. Plant Physiol. 175, 1593–1607 (2017).
Guilford, W. J., Schneider, D. M., Labovitz, J. & Opella, S. J. High resolution solid state C NMR spectroscopy of sporopollenins from different plant taxa. Plant Physiol. 86, 134–136 (1988).
Mao, J., Cory, R. M., McKnight, D. M. & Schmidt-Rohr, K. Characterization of a nitrogen-rich fulvic acid and its precursor algae from solid state NMR. Org. Geochem. 38, 1277–1292 (2007).
Mao, J.-D. et al. Abundant and stable char residues in soils: implications for soil fertility and carbon sequestration. Environ. Sci. Technol. 46, 9571–9576 (2012).
Johnson, R. L. & Schmidt-Rohr, K. Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization. J. Magn. Reson. 239, 44–49 (2014).
Kim, S. S., Grienenberger, E. & Lallemand, B. LAP6/POLYKETIDE SYNTHASE A and LAP5/POLYKETIDE SYNTHASE B encode hydroxyalkyl α-pyrone synthases required for pollen development and sporopollenin biosynthesis in Arabidopsis thaliana. Plant Cell 22, 4045–4066 (2010).
Grienenberger, E. et al. Analysis of TETRAKETIDE α-PYRONE REDUCTASE function in Arabidopsis thaliana reveals a previously unknown, but conserved, biochemical pathway in sporopollenin monomer biosynthesis. Plant Cell 22, 4067–4083 (2010).
Rasouli, M., Ostovar-Ravari, A. & Shokri-Afra, H. Characterization and improvement of phenol-sulfuric acid microassay for glucose-based glycogen. Eur. Rev. Med. Pharmacol. Sci. 18, 2020–2024 (2014).
Mao, J. D. & Schmidt-Rohr, K. Accurate quantification of aromaticity and nonprotonated aromatic carbon fraction in natural organic matter by 13C solid-state nuclear magnetic resonance. Environ. Sci. Technol. 38, 2680–2684 (2004).
Mao, J.-D. & Schmidt-Rohr, K. Methylene spectral editing in solid-state 13C NMR by three-spin coherence selection. J. Magn. Reson. 176, 1–6 (2005).
Liu, R., He, B. & Chen, X. Degradation of poly(vinyl butyral) and its stabilization by bases. Polym. Degrad. Stab. 93, 846–853 (2008).
Weng, J.-K. & Chapple, C. The origin and evolution of lignin biosynthesis. New Phytol. 187, 273–285 (2010).
Hayatsu, R., Botto, R. E., McBeth, R. L., Scott, R. G. & Winans, R. Chemical structure of a sporinite from a lignite: comparison with a synthetic sporinite transformed from sporopollenin. Prepr. Pap. Am. Chem. Soc. Div. Fuel Chem. 32, 1–8 (1987).
Dobritsa, A. A. et al. CYP704B1 is a long-chain fatty acid ω-hydroxylase essential for sporopollenin synthesis in pollen of Arabidopsis. Plant Physiol. 151, 574–589 (2009).
Morant, M. et al. CYP703 is an ancient cytochrome P450 in land plants catalyzing in-chain hydroxylation of lauric acid to provide building blocks for sporopollenin synthesis in pollen. Plant Cell 19, 1473–1487 (2007).
Austin, M. B. & Noel, J. P. The chalcone synthase superfamily of type III polyketide synthases. Nat. Prod. Rep. 20, 79–110 (2003).
De Azevedo Souza, C. et al. A novel fatty Acyl-CoA Synthetase is required for pollen development and sporopollenin biosynthesis in Arabidopsis. Plant Cell 21, 507–525 (2009).
Shibuya, T., Funamizu, M. & Kitahara, Y. Novel p-coumaric acid esters from Pinus densiflora pollen. Phytochemistry 17, 979–981 (1978).
This work was supported by the Pew Scholar Program in the Biomedical Sciences (J.-K.W.) and the Searle Scholars Program (J.-K.W.). The solid-state NMR part of this work (by P.P. and M.H.) was supported by the Center for Lignocellulose Structure and Formation, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award number DE-SC0001090.
The authors declare no competing interests.
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Li, FS., Phyo, P., Jacobowitz, J. et al. The molecular structure of plant sporopollenin. Nature Plants 5, 41–46 (2019). https://doi.org/10.1038/s41477-018-0330-7
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