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The Root Cap Cuticle: A Cell Wall Structure for Seedling Establishment and Lateral Root Formation

Berhin, Alice, de Bellis, Damien, Franke, Rochus B., Buono, Rafael A., Nowack, Moritz K., Nawrath, Christiane
Cell 2019 v.176 no.6 pp. 1367-1378.e8
abiotic stress, biosynthesis, cell walls, cutin, deformation, genes, hypersensitivity, mutation, plant cuticle, plant establishment, plant organs, root cap, root primordia, stem cells, ultrastructure
The root cap surrounding the tip of plant roots is thought to protect the delicate stem cells in the root meristem. We discovered that the first layer of root cap cells is covered by an electron-opaque cell wall modification resembling a plant cuticle. Cuticles are polyester-based protective structures considered exclusive to aerial plant organs. Mutations in cutin biosynthesis genes affect the composition and ultrastructure of this cuticular structure, confirming its cutin-like characteristics. Strikingly, targeted degradation of the root cap cuticle causesĀ a hypersensitivity to abiotic stresses during seedling establishment. Furthermore, lateral root primordia also display a cuticle that, when defective, causes delayed outgrowth and organ deformations, suggesting that it facilitates lateral root emergence. Our results show that the previously unrecognized root cap cuticle protects the root meristem during the critical phase of seedling establishment and promotes the efficient formation of lateral roots.