Identification of tannic cell walls at the outer surface of the endosperm upon Arabidopsis seed coat rupture.

Lara Demonsais,Luis Lopez‐Molina,Sylvain Loubéry,Anne Utz‐Pugin

doi:10.1111/tpj.14994

Abstract

SUMMARYThe seed coat is specialized dead tissue protecting the plant embryo from mechanical and oxidative damage. Tannins, a type of flavonoids, are antioxidants known to accumulate in the Arabidopsis seed coat and transparent testa mutant seeds, deficient in flavonoid synthesis, exhibit low viability. However, their precise contribution to seed coat architecture and biophysics remains evasive. A seed coat cuticle, covering the endosperm outer surface and arising from the seed coat inner integument 1 cell layer was, intriguingly, previously shown to be more permeable in transparent testa mutants deficient not in cuticular component synthesis, but rather in flavonoid synthesis. Investigating the role of flavonoids in cuticle permeability led us to identify periclinal inner integument 1 tannic cell walls being attached, together with the cuticle, to the endosperm surface upon seed coat rupture. Hence, inner integument 1 tannic cell walls and the cuticle form two fused layers present at the surface of the exposed endosperm upon seed coat rupture, regulating its permeability. Their potential physiological role during seed germination is discussed.

Highlights

Seeds are a late land plant evolution innovation consisting of plant embryos maintained in a desiccated and highly sheltered state surrounded by a protective dead seed coat of maternal origin
A type of flavonoids, are antioxidants known to accumulate in the Arabidopsis seed coat and transparent testa mutant seeds, deficient in flavonoid synthesis, exhibit low viability
We show that tannic cell walls remain attached to the endosperm upon seed coat rupture, participating in its permeability properties

Summary

SUMMARY

The seed coat is specialized dead tissue protecting the plant embryo from mechanical and oxidative damage. A type of flavonoids, are antioxidants known to accumulate in the Arabidopsis seed coat and transparent testa mutant seeds, deficient in flavonoid synthesis, exhibit low viability. Their precise contribution to seed coat architecture and biophysics remains evasive. Inner integument 1 tannic cell walls and the cuticle form two fused layers present at the surface of the exposed endosperm upon seed coat rupture, regulating its permeability. Their potential physiological role during seed germination is discussed.

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