title: Development of flower buds in the Japanese pear (Pyrus pyrifolia) from late autumn to early spring.
abstract: We periodically investigated the lateral flower bud morphology of 1-year shoots of 'Kosui' pears (Pyrus pyrifolia Nakai) in terms of dormancy progression, using magnetic resonance imaging. The size of flower buds did not change significantly during endodormancy, but rapid enlargement took place at the end of the ecodormancy stage. To gain insight into the physiological status during this period, we analyzed gene expression related to cell cycle-, cell expansion- and water channel-related genes, namely cyclin (CYC), expansin (EXPA), tonoplast intrinsic proteins (TIP) and plasma membrane intrinsic proteins (PIP). Constant but low expression of pear cyclin genes (PpCYCD3s) was observed in the transition phase from endodormancy to ecodormancy. The expression levels of PpCYCD3s were consistent with few changes in flower bud size, but up-regulated before the sprouting stage. In contrast, the expression of pear expansin and water channel-related genes (PpEXPA2, PpPIP2A, PpPIP2B, PpIδTIP1A and PpIδTIP1B) were low until onset of the rapid enlargement stage of flower buds. However, expression of these genes rapidly increased during sprouting along with a gradual increase of free water content in the floral primordia of buds. Taken together, these results suggest that flower bud size tends to stay constant until the endodormancy phase transition. Rapid enlargement of flower buds observed in March is partly due to the enhancement of the cell cycle. Then, sprouting takes place concomitant with the increase in cell expansion and free water movement.
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, 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: Pham Anh
authors.initials: PA
authors.lastname: Tuan
authors.affiliation: National Food Research Institute, NARO, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
authors.forename: Akemi
authors.initials: A
authors.lastname: Katsumi-Horigane
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan.
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: Akiko
authors.initials: A
authors.lastname: Ito
authors.affiliation: National Food Research Institute, NARO, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Sekiyama
authors.affiliation: National Food Research Institute, NARO, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ono
authors.affiliation: NARO Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan takaya@affrc.go.jp.
authors.forename: Takaya
authors.initials: T
authors.lastname: Moriguchi
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D035264:Flowers / Q000033:anatomy & histology / Q000166:cytology / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008954:Models, Biological; D057445:Plant Dormancy; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D031989:Pyrus / Q000033:anatomy & histology / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D012621:Seasons; D014867:Water / Q000378:metabolism
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D014867:Water
keywords: cell cycle; cell expansion; flower bud development; magnetic resonance imaging (MRI); water channel