TBL38 atypical homogalacturonan-acetylesterase activity and cell wall microdomain localization in Arabidopsis seed mucilage secretory cells

• Published in: iScience 2024-05, Vol.27 (5), p.109666-109666, Article 109666
• Main Authors: Dauphin, Bastien G., Ropartz, David, Ranocha, Philippe, Rouffle, Maxime, Carton, Camille, Le Ru, Aurélie, Martinez, Yves, Fourquaux, Isabelle, Ollivier, Simon, Mac-Bear, Jessica, Trezel, Pauline, Geairon, Audrey, Jamet, Elisabeth, Dunand, Christophe, Pelloux, Jérôme, Ralet, Marie-Christine, Burlat, Vincent
• Format: Article
• Language: English
• Subjects: Biochemistry, Molecular Biology; Food engineering; Life Sciences; Plant biology; Plant cytology; Plant development
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2024.109666

Plant cell walls constitute complex polysaccharidic/proteinaceous networks whose biosynthesis and dynamics implicate several cell compartments. The synthesis and remodeling of homogalacturonan pectins involve Golgi-localized methylation/acetylation and subsequent cell wall-localized demethylation/deacetylation. So far, TRICHOME BIREFRINGENCE-LIKE (TBL) family members have been described as Golgi-localized acetyltransferases targeting diverse hemicelluloses or pectins. Using seed mucilage secretory cells (MSCs) from Arabidopsis thaliana, we demonstrate the atypical localization of TBL38 restricted to a cell wall microdomain. A tbl38 mutant displays an intriguing homogalacturonan immunological phenotype in this cell wall microdomain and in an MSC surface-enriched abrasion powder. Mass spectrometry oligosaccharide profiling of this fraction reveals an increased homogalacturonan acetylation phenotype. Finally, TBL38 displays pectin acetylesterase activity in vitro. These results indicate that TBL38 is an atypical cell wall-localized TBL that displays a homogalacturonan acetylesterase activity rather than a Golgi-localized acetyltransferase activity as observed in previously studied TBLs. TBL38 function during seed development is discussed. [Display omitted] •Known plant TBLs are Golgi-localized acetyltransferases for cell wall polysaccharides•TBL38 is peculiarly localized to a wall microdomain in Arabidopsis seed epidermis•TBL38 has an uncommon acetylesterase activity targeted toward homogalacturonans•TBL38 is a new actor of the complex maturation of plant cell wall polysaccharides Plant biology; Plant cytology; Plant development;