Journal Article

Ethylene signaling induces gelatinous layers with typical features of tension wood in hybrid aspen

Björn Sundberg, Ewa J. Mellerowicz, Judith Felten, Jorma Vahala, Nicolas Delhomme, Markus Rüggeberg, Joanna Leśniewska, Jaakko Kangasjärvi, Torgeir R. Hvidsten, Jonathan Love, András Gorzsás

2018

Overview

The phytohormone ethylene impacts secondary stem growth in plants by stimulating cambial activity, xylem development and fiber over vessel formation. We report the effect of ethylene on secondary cell wall formation and the molecular connection between ethylene signaling and wood formation. We applied exogenous ethylene or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) to wild-type and ethylene-insensitive hybrid aspen trees (Populustremula × tremuloides) and studied secondary cell wall anatomy, chemistry and ultrastructure. We furthermore analyzed the transcriptome (RNA Seq) after ACC application to wildtype and ethylene-insensitive trees. We demonstrate that ACC and ethylene induce gelatinous layers (G-layers) and alter the fiber cell wall cellulose microfibril angle. G-layers are tertiary wall layers rich in cellulose, typically found in tension wood of aspen trees. A vast majority of transcripts affected by ACC are downstream of ethylene perception and include a large number of transcription factors (TFs). Motif-analyses reveal potential connections between ethylene TFs (Ethylene Response Factors (ERFs), ETHYLENE INSENSITIVE 3/ETHYLENE INSENSITIVE3-LIKE1 (EIN3/EIL1)) and wood formation. G-layer formation upon ethylene application suggests that the increase in ethylene biosynthesis observed during tension wood formation is important for its formation. Ethylene-regulated TFs of the ERF and EIN3/EIL1 type could transmit the ethylene signal.

• Publisher: New Phytologist Trust,Wiley Subscription Services, Inc
• Subject: 1-aminocyclopropane-1-carboxylic acid / Biochemistry and Molecular Biology / Biokemi och molekylärbiologi / Biosynthesis / Botanik / Botany / cambium / Carboxylic acids / Cell Biology / cell wall / Cell walls / Cellbiologi / Cellulose / Cellulose fibers / cellulose microfibrils / Deciduous trees / Ethene / Ethylene / ethylene production / ethylene signaling / fiber cells / gelatinous layer (G‐layer) / Gene expression / hybrid aspen / hybrids / Nucleic acids / Plant growth substances / Plant hormones / Populus tremula / Populus tremuloides / Ribonucleic acid / RNA / Signaling / stem elongation / Tension / tension wood / Tertiary / Transcription / Transcription factors / transcriptome / Trees / Ultrastructure / Wood / Xylem