title: Physiological differences between bud breaking and flowering after dormancy completion revealed by DAM and FT/TFL1 expression in Japanese pear (Pyrus pyrifolia).
abstract: The regulatory mechanisms underlying bud breaking (scale leaf elongation) and flowering in the lateral flower buds of Japanese pear (Pyrus pyrifolia Nakai 'Kosui') are unknown. To more fully characterize these processes, we treated pear trees with different amounts of chilling initiated at different times. Chilling for ∼900 h at 6 °C always induced bud breaking (scale elongation in ≥70% lateral flower bud) when provided between October and February, whereas chilling provided earlier (between October and December) was less effective on flowering (floret growth and development) than later chilling and the flowering rate increased with longer chilling durations. During chilling, the expression of pear DAMs (PpMADS13-1, 13-2 and 13-3) in lateral flower buds decreased as chilling accumulated irrespective of the timing of chilling. In addition, pear TFL1 (PpTFL1-1a) in the lateral flower buds was expressed at higher levels when the time interval for chilling was earlier. On the other hand, during forcing at 15 °C after chilling, the expression pattern of all three PpMADS13 genes was similar among the treatments, and the expression levels seemed lower in the treatment where scale leaves of the lateral flower bud elongated faster, whereas pear FT (PpFT2a) was expressed at higher levels in the buds whose flower clusters elongated more vigorously during forcing. From these results, we infer that flowering time may be mediated via the balance of flowering-related genes FT and TFL1, whereas bud breaking may be regulated via the DAM genes in Japanese pear.
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan akiko@affrc.go.jp.
authors.forename: Akiko
authors.initials: A
authors.lastname: Ito
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan Present address: Graduate School of Horticulture, Chiba University, Matsudo, Chiba 271-8510, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Saito
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sakamoto
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Sugiura
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan Present address: Department of Horticulture, The State Agricultural Ministry's Key Laboratory of Horticultural Plant Growth, Development & Quality Improvement, Zhejiang University, Hangzhou, Zhejiang Province 310058, China.
authors.forename: Songling
authors.initials: S
authors.lastname: Bai
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan.
authors.forename: Takaya
authors.initials: T
authors.lastname: Moriguchi
mesh_terms: D003080:Cold Temperature; D035264:Flowers / Q000235:genetics / Q000502:physiology; D015870:Gene Expression; D017343:Genes, Plant; D026161:MADS Domain Proteins / Q000235:genetics; D057445:Plant Dormancy / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics; D031989:Pyrus / Q000235:genetics* / Q000502:physiology*
chemical_list: D026161:MADS Domain Proteins; D010940:Plant Proteins
keywords: bloom; bud scale elongation; chill requirement