Editor’s summary
Cell layers can slip, slide, and fold in among one another during development to generate the complex forms of the biological world. Studying a small aquatic carnivorous plant as well as the land-locked mustard plant Arabidopsis, Kelly-Bellow et al. built a connection from genes driving a hormone’s biosynthesis to the curved shapes of the mature plants. The plant hormone brassinosteroid reduces mechanical constraints imposed by the plant’s epidermis, thus allowing internal cell layers to drive the formation of new shapes with development. —Pamela J. Hines
Abstract
Growth coordination between cell layers is essential for development of most multicellular organisms. Coordination may be mediated by molecular signaling and/or mechanical connectivity between cells, but how genes modify mechanical interactions between layers is unknown. Here we show that genes driving brassinosteroid synthesis promote growth of internal tissue, at least in part, by reducing mechanical epidermal constraint. We identified a brassinosteroid-deficient dwarf mutant in the aquatic plant Utricularia gibba with twisted internal tissue, likely caused by mechanical constraint from a slow-growing epidermis. We tested this hypothesis by showing that a brassinosteroid mutant in Arabidopsis enhances epidermal crack formation, indicative of increased tissue stress. We propose that by remodeling cell walls, brassinosteroids reduce epidermal constraint, showing how genes can control growth coordination between layers by means of mechanics.
