title: Plasma membrane-anchored chloroplasts are necessary for the gravisensing system of Ceratopteris richardii prothalli.
abstract: The prothalli of the fern Ceratopteris richardii exhibit negative gravitropism when grown in darkness. However, no sedimentable organelles or substances have been detected in the prothallial cells, suggesting that a non-sedimentable gravisensor exists. We investigated whether chloroplasts are involved in the gravisensing system of C. richardii prothalli. We used a clumped-chloroplast mutant, clumped chloroplast 1 (cp1), in which the chloroplasts are detached from the plasma membrane and clustered around the nucleus likely because of a partial deletion in the KINESIN-LIKE PROTEIN FOR ACTIN-BASED CHLOROPLAST MOVEMENT 1 gene. The cp1 mutation resulted in prothalli that had a significantly diminished gravitropic response, while the phototropic response occurred normally. These results suggest that plasma membrane-anchored chloroplasts in prothallial cells function as one of the gravisensors in C. richardii prothalli.
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan. kamachi@sci.u-toyama.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kamachi
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan.|Division of Functional Genomics, Advanced Science Research Center, Kanazawa University, Takara-machi 13-1, Kanazawa, Ishikawa, 920-0934, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tamaoki
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan.
authors.forename: Ichirou
authors.initials: I
authors.lastname: Karahara
mesh_terms: D002462:Cell Membrane / Q000502:physiology; D002736:Chloroplasts / Q000235:genetics / Q000502:physiology; D055993:Germ Cells, Plant / Q000254:growth & development / Q000502:physiology; D018522:Gravitropism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D029625:Pteridaceae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
chemical_list: D010940:Plant Proteins
keywords: Ceratopteris richardii; Fern gametophyte; Gravitropism; Gravity perception