title: Role of LOTR1 in Nutrient Transport through Organization of Spatial Distribution of Root Endodermal Barriers.
abstract: The formation of Casparian strips and suberin lamellae at the endodermis limits the free diffusion of nutrients and harmful substances via the apoplastic space between the soil solution and the stele in roots [1-3]. Casparian strips are ring-like lignin polymers deposited in the middle of anticlinal cell walls between endodermal cells and fill the gap between them [4-6]. Suberin lamellae are glycerolipid polymers covering the endodermal cells and likely function as a barrier to limit transmembrane movement of apoplastic solutes into the endodermal cells [7, 8]. However, the current knowledge on the formation of these two distinct endodermal barriers and their regulatory role in nutrient transport is still limited. Here, we identify an uncharacterized gene, LOTR1, essential for Casparian strip formation in Arabidopsis thaliana. The lotr1 mutants display altered localization of CASP1, an essential protein for Casparian strip formation [9], disrupted Casparian strips, ectopic suberization of endodermal cells, and low accumulation of shoot calcium (Ca). Degradation by expression of a suberin-degrading enzyme in the mutants revealed that the ectopic suberization at the endodermal cells limits Ca transport through the transmembrane pathway, thereby causing reduced Ca delivery to the shoot. Moreover, analysis of the mutants showed that suberin lamellae function as an apoplastic diffusion barrier to the stele at sites of lateral root emergence where Casparian strips are disrupted. Our findings suggest that the transmembrane pathway through unsuberized endodermal cells, rather than the sites of lateral root emergence, mediates the transport of apoplastic substances such as Ca into the xylem.
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.
authors.forename: Baohai
authors.initials: B
authors.lastname: Li
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Kamiya
authors.affiliation: Department of Plant Molecular Biology, University of Lausanne-Sorge, 1015 Lausanne, Switzerland.
authors.forename: Lothar
authors.initials: L
authors.lastname: Kalmbach
authors.affiliation: Department of Radioecology, Institute for Environmental Sciences, Aomori 039-3212, Japan.
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Yamagami
authors.affiliation: NIBB Core Research Facilities, National Institute for Basic Biology, Aichi 444-8585, Japan.
authors.forename: Katsushi
authors.initials: K
authors.lastname: Yamaguchi
authors.affiliation: NIBB Core Research Facilities, National Institute for Basic Biology, Aichi 444-8585, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Shigenobu
authors.affiliation: Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Sawa
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK.
authors.forename: John M C
authors.initials: JM
authors.lastname: Danku
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK.
authors.forename: David E
authors.initials: DE
authors.lastname: Salt
authors.affiliation: Department of Plant Molecular Biology, University of Lausanne-Sorge, 1015 Lausanne, Switzerland.
authors.forename: Niko
authors.initials: N
authors.lastname: Geldner
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan. Electronic address: atorufu@mail.ecc.u-tokyo.ac.jp.
authors.forename: Toru
authors.initials: T
authors.lastname: Fujiwara
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D001692:Biological Transport; D002473:Cell Wall / Q000378:metabolism; D004707:Endoderm / Q000378:metabolism; D008031:Lignin / Q000378:metabolism; D008055:Lipids / Q000502:physiology; D018517:Plant Roots / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C000627944:LOTR1 protein, Arabidopsis; D008055:Lipids; C065875:suberin; D008031:Lignin
keywords: Casparian strip; apoplast; calcium transport; cell wall; lateral root; suberin; transmembrane pathway