title: Chitin Nanofiber Elucidates the Elicitor Activity of Polymeric Chitin in Plants.
abstract: Chitin, an N-acetyl-D-glucosamine polymer, is a component of fungal cell walls and a microbe/pathogen-associated molecular pattern that elicits plant defense responses. As polymeric chitin is difficult to handle due to its insolubility in water, many studies on chitin-induced immune responses have used water-soluble low-molecular weight chitin instead. Thus, it is unclear if polymeric chitin can induce resistance. Here, we examined the elicitor activity of chitin nanofiber (CNF) of submicron thickness prepared from polymeric chitin. CNF showed a high dispersing ability in water and induced both reactive oxygen species (ROS) production and chitin-induced defense-related gene expression in Arabidopsis thaliana seedlings. The Arabidopsis chitin elicitor receptor kinase 1 (Atcerk1) mutant, which is impaired in chitin perception, also failed to respond to CNF. CNF exposure triggered ROS generation in suspension-cultured cells from Oryza sativa. Furthermore, pre-treatment of Arabidopsis leaves with CNF effectively reduced pathogen infection by both the fungus Alternaria brassicicola and the bacterium Pseudomonas syringae pv. tomato DC3000. These results demonstrate that CNF has elicitor activity and will help define the role of polymeric chitin in plant immune responses.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University Tottori, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Egusa
authors.affiliation: RIKEN Center for Sustainable Resource Science Yokohama, Japan ; Graduate School of Environmental and Life Science, Okayama University Okayama, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University Tottori, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Urakami
authors.affiliation: Faculty of Agriculture, Tottori University Tottori, Japan.
authors.forename: Sanami
authors.initials: S
authors.lastname: Okuda
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University Tottori, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Ifuku
authors.affiliation: RIKEN Center for Sustainable Resource Science Yokohama, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Nakagami
authors.affiliation: Faculty of Agriculture, Tottori University Tottori, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Kaminaka
keywords: Alternaria brassicicola; Arabidopsis thaliana; Pseudomonas syringae pv. tomato DC3000; chitin; elicitor; nanofiber; rice