Polygalacturonase-inhibiting Proteins Contribute to Primary Cell Wall Degradation during Xylem Vessel Differentiation
Chaokun Huang (Japan)1; Erika Yamada (Japan)2; Ya Ma (Japan)2; Eri Kamon (Japan)3; Nobuhiro Akiyoshi (Japan)4; Toshihisa Kotake (Japan)5; Josip Safran (France)6; Valérie Lefebvre (France)6; Jérôme Pelloux (France)6; Misato Ohtani (Japan)1 2 7 8;
1 - Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; 2 - Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan; 3 - College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu 525-8577, Shiga, Japan; 4 - Department of Life Science, Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan; 5 - Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku,Saitama 338-8570, Japan; 6 - UMRT INRAE 1158 BioEcoAgro-BIOPI Biologie des Plantes et Innovation, Université de Picardie, 33 Rue St Leu, Amiens 80039, France; 7 - Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan; 8 - RIKEN, Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan;
Keywords: Primary cell wall; Xylem differentiation; Polygalacturonase activity;
Abstract Topics: Theme 5: Cell Wall Proteins
Type of Presentation: Oral Communication
Abstract text: Cell wall remodeling is a critical process for xylem vessel functionality, and one of the targets of remodeling is pectic fractions in the primary cell wall. Previously, the interaction mechanism of pathogen-derived polygalacturonases (PGs), pectin degradation enzymes, and plant PG-inhibiting proteins (PGIPs) has been documented. Here, we investigated potential roles of plant PGIPs in regulating endogenous PGs during xylem development. Transcript analysis revealed that the PGIP genes expressed in seedlings were induced by overexpression of VND7, a master regulator of xylem formation. They were also upregulated in cotyledons upon phytohormone-induced system of xylem formation. The fluorescent tdTomato reporter lines demonstrated the expression of these PGIPs in the cytoplasm of vascular cells, and especially in the early stages of xylem vessel development. The BiFC assay supported interactions between PGIPs and endogenous PGs at the cell wall / apoplastic region. Moreover, xylem vessel–specific overexpression of PGIPs compromised transport capacity in seedling roots, whereas their loss-of-function mutants showed improved transport capacity. Finally, the total PG activity was found to be increased in the mutant seedlings. Our findings suggest that PGIPs modulate endogenous PGs for the regulation of xylem vessel functionality.