Evolutionary stasis of sporopollenin biochemistry revealed by unaltered Pennsylvanian spores.
The biopolymer sporopollenin present in the spore/pollen walls of all land plants is regarded as one of the most recalcitrant biomacromolecules (biopolymers), providing protection against a range of abiotic stresses. This long-term stability is demonstrated by the near-ubiquitous presence of pollen and spores in the fossil record with spores providing the first evidence for the colonization of the land. Here, we report for the first time chemical analyses of geologically unaltered sporopollenin from Pennsylvanian (c. 310 million yr before present (MyBP)) cave deposits. Our data show that Pennsylvanian Lycophyta megaspore sporopollenin has a strong chemical resemblance to extant relatives and indicates that a co-polymer model of sporopollenin formation is the most likely configuration. Broader comparison indicates that extant sporopollenin structure is similar across widely spaced phylogenetic groups and suggests land plant sporopollenin structure has remained stable since embryophytes invaded land.
School of Geosciences, The University of Edinburgh, West Mains Road, Edinburgh, EH9 3JN, UK.|Department of Environment Earth and Ecosystems, The Open University, Milton Keynes, MK7 6AA, UK.
W T
WT
Fraser
Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK.
A C
AC
Scott
Department of Environment Earth and Ecosystems, The Open University, Milton Keynes, MK7 6AA, UK.
A E S
AES
Forbes
Department of Geology, Field Museum of Natural History, 1400 S. Lake Shore Drive, Chicago, IL, 60605, USA.
I J
IJ
Glasspool
Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL, 60607, USA.
R E
RE
Plotnick
Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL, 60607, USA.
F
F
Kenig
The School of Biosciences, Division of Agricultural and Environmental Sciences, The University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire, LE12 5RD, UK.
B H
BH
Lomax
D001704:Biopolymers / Q000737:chemistry*; D002338:Carotenoids / Q000737:chemistry*; D019143:Evolution, Molecular; D010414:Pennsylvania; D010944:Plants / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013170:Spores / Q000737:chemistry* / Q000648:ultrastructure
D001704:Biopolymers; C009800:sporopollenin; D002338:Carotenoids