title: Branch regeneration induced by sever damage in the brown alga Dictyota dichotoma (dictyotales, phaeophyceae).
abstract: Tissue wounds are mainly caused by herbivory, which is a serious threat for macro-algae, and brown algae are known to regenerate branches or buds in response to wounding. In the present paper, we describe a branch regeneration system, induced by sever damage, in the brown alga Dictyota dichotoma. Segmentations of juvenile thalli induced branch regenerations unless explants possessed apical cells. Apical excisions in distinct positions elucidated that disruption of an apical cell or disconnection of tissue with an apical cell triggered the branch regeneration. Furthermore, spatial positions of regenerated branches seemed to be regulated by the apical region, which was assumed to generate inhibitory effects for lateral branch regeneration. Mechanical incision, which disrupted tissue continuity with the apical region, induced branch regeneration preferentially below the incision. Although we were unable to identify the candidate inhibitory substance, our results suggested that the apical region may have an inhibitory effect on lateral branch regeneration. Additionally, observations of branch regeneration showed that all epidermal cells in D. dichotoma possess the ability to differentiate into apical cells, directly. This may be the first report of algal transdifferentiation during the wound-stress response.
authors.affiliation: Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran, 051-0013, Japan. atsuko72tanaka@gmail.com.|Faculty of Science, University of the Ryukyus, Nishihara, Okinawa, 903-0213, Japan. atsuko72tanaka@gmail.com.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Tanaka
authors.affiliation: Experiment Farm, Field Science Center for Northern Biosphere, Hokkaido University, Sapporo, 060-0811, Japan.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Hoshino
authors.affiliation: Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran, 051-0013, Japan.
authors.forename: Chikako
authors.initials: C
authors.lastname: Nagasato
authors.affiliation: Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran, 051-0013, Japan.
authors.forename: Taizo
authors.initials: T
authors.lastname: Motomura
mesh_terms: D002454:Cell Differentiation / Q000502:physiology*; D054338:Cell Transdifferentiation / Q000502:physiology*; D000459:Phaeophyceae / Q000254:growth & development* / Q000502:physiology; D019441:Plant Epidermis / Q000166:cytology*; D012038:Regeneration / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology
keywords: Apical dominance; Regeneration; Signal propagation; Transdifferentiation; Wound stress