Etiolated Seedling Development Requires Repression of Photomorphogenesis by a Small Cell-Wall-Derived Dark Signal

Scott A. Sinclair, Camille Larue, Laura Bonk, Asif Khan, Hiram Castillo-Michel, Ricardo J. Stein, Daniel Grolimund, Dominik Begerow, Ulla Neumann, Michael J. Haydon, Ute Krämer
2017 Current Biology  
Etiolated growth in darkness or the irreversible transition to photomorphogenesis in the light engages alternative developmental programs operating across all organs of a plant seedling. Darkgrown Arabidopsis de-etiolated by zinc (dez) mutants exhibit morphological, cellular, metabolic, and transcriptional characteristics of light-grown seedlings. We identify the causal mutation in TRICHOME BIREFRINGENCE encoding a putative acyl transferase. Pectin acetylation is decreased in dez, as previously
more » ... found in the reduced wall acetyla-tion2-3 mutant, shown here to phenocopy dez. Moreover, pectin of dez is excessively methylesterified. The addition of very short fragments of homogalacturonan, tri-galacturonate, and tetra-galacturonate, restores skotomorphogenesis in dark-grown dez and similar mutants, suggesting that the mutants are unable to generate these de-methylesterified pectin fragments. In combination with genetic data, we propose a model of spatiotemporally separated photoreceptive and signal-responsive cell types, which contain overlapping subsets of the regulatory network of light-dependent seedling development and communicate via a pectin-derived dark signal.
doi:10.1016/j.cub.2017.09.063 pmid:29103938 fatcat:z4loin5vlfbg3fyy66x26ncqfi