title: Light Inhibition of Shoot Regeneration Is Regulated by Endogenous Abscisic Acid Level in Calli Derived from Immature Barley Embryos.
abstract: Shoot regeneration in calli derived from immature barley embryos is regulated by light conditions during the callus-induction period. Barley cultivars Kanto Nijo-5 (KN5) and K-3 (K3) showed lower efficiency of shoot regeneration in a 16-h photoperiod during callus-induction than those in continuous darkness, whereas shoot regeneration was enhanced in cultures under a 16-h photoperiod in Golden Promise (GP) and Lenins (LN). These cultivars were classified as photo-inhibition type (KN5 and K3) or photo-induction type (GP and LN) according to their response to light. Contents of endogenous plant hormones were determined in calli cultured under a 16-h photoperiod and continuous darkness. In photo-inhibition type, higher accumulation of abscisic acid (ABA) was detected in calli cultured under a 16-h photoperiod, whereas calli showed lower levels of endogenous ABA in continuous darkness. However, cultivars of photo-induction type showed lower levels of ABA in calli cultured under both light conditions, similarly to photo-inhibition type in continuous darkness. Exogenous ABA inhibited the callus growth and shoot regeneration independent of light conditions in all cultivars. In photo-inhibition type, lower levels of endogenous ABA induced by ABA biosynthesis inhibitor, fluridone, reduced the photo-inhibition of shoot regeneration. Expression of ABA biosynthesis gene, HvNCED1, in calli was regulated by the light conditions. Higher expression was observed in calli cultured under a 16-h photoperiod. These results indicate that ABA biosynthesis could be activated through the higher expression of HvNCED1 in a 16-h photoperiod and that the higher accumulations of ABA inhibit shoot regeneration in the photo-inhibition type cultivars.
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan.
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Rikiishi
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Matsuura
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ikeda
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Maekawa
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D053898:Biosynthetic Pathways / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D017343:Genes, Plant; D001467:Hordeum / Q000187:drug effects / Q000196:embryology* / Q000235:genetics / Q000528:radiation effects; D008027:Light; D010937:Plant Growth Regulators / Q000494:pharmacology; D018520:Plant Shoots / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011728:Pyridones / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012038:Regeneration / Q000187:drug effects* / Q000528:radiation effects; D012639:Seeds / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D046509:Tissue Culture Techniques
chemical_list: D010937:Plant Growth Regulators; D011728:Pyridones; D012333:RNA, Messenger; C013351:fluridone; D000040:Abscisic Acid