Casparian strip diffusion barrier in Arabidopsis is made of a lignin polymer without suberin

Casparian strips are ring-like cell-wall modifications in the root endodermis of vascular plants. Their presence generates a paracellular barrier, analogous to animal tight junctions, that is thought to be crucial for selective nutrient uptake, exclusion of pathogens, and many other processes. Despi...

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Published in:Proceedings of the National Academy of Sciences - PNAS 2012-06, Vol.109 (25), p.10101-10106
Main Authors: Naseer, Sadaf, Lee, Yuree, Lapierre, Catherine, Franke, Rochus, Nawrath, Christiane, Geldner, Niko
Format: Article
Language:English
Subjects:
Agricultural sciences
animals
Arabidopsis
Arabidopsis - physiology
Biological Sciences
Biopolymers - physiology
Biosynthesis
Cell walls
Cells
chemical analysis
Endodermis
eukaryotic cells
Flowers & plants
Life Sciences
Lignin
Lignin - physiology
Lipids - physiology
Memory interference
Molecular structure
Monomers
nutrient uptake
pathogens
Plant roots
Plants
Polymers
Seedlings
suberin
tight junctions
vascular plants
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Summary:Casparian strips are ring-like cell-wall modifications in the root endodermis of vascular plants. Their presence generates a paracellular barrier, analogous to animal tight junctions, that is thought to be crucial for selective nutrient uptake, exclusion of pathogens, and many other processes. Despite their importance, the chemical nature of Casparian strips has remained a matter of debate, confounding further molecular analysis. Suberin, lignin, lignin-like polymers, or both, have been claimed to make up Casparian strips. Here we show that, in Arabidopsis , suberin is produced much too late to take part in Casparian strip formation. In addition, we have generated plants devoid of any detectable suberin, which still establish functional Casparian strips. In contrast, manipulating lignin biosynthesis abrogates Casparian strip formation. Finally, monolignol feeding and lignin-specific chemical analysis indicates the presence of archetypal lignin in Casparian strips. Our findings establish the chemical nature of the primary root-diffusion barrier in Arabidopsis and enable a mechanistic dissection of the formation of Casparian strips, which are an independent way of generating tight junctions in eukaryotes.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1205726109