UPSC-0017
Ethylene signaling induces gelatinous layers with typical features of tension wood in hybrid aspen
The phytohormone ethylene has the potential to regulate secondary stem growth in plants. Application of exogenous ethylene, or of its in planta precursor 1-aminocyclopropane-1-carboxylic acid (ACC), to wild type and ethylene insensitive trees, has previously been shown to stimulate typical attributes of tension wood such as xylem growth and vessel frequency in stems of hybrid aspen (Populus tremula x tremuloides) in an ethylene-signaling dependent way. The present study demonstrates that ACC and ethylene also induced typical gelatinous-layers (G-layers) and altered the cellulose microfibril angle in secondary cell wall layers in hybrid aspen fibers through ethylene-signaling. G-layers are tertiary wall layers rich in cellulose, typically found in tension wood of aspen trees. This observation further strengthens the concept that the increase in ethylene biosynthesis observed in association with tension wood formation is a key signaling component that triggers tension wood formation. RNA-Seq data in combination with motif-analysis in promoters of regulated genes downstream of ethylene-signaling highlights potential molecular connections between ethylene signaling and tension wood formation.