title: Release of apical dominance in potato tuber is accompanied by programmed cell death in the apical bud meristem.
abstract: Potato (Solanum tuberosum) tuber, a swollen underground stem, is used as a model system for the study of dormancy release and sprouting. Natural dormancy release, at room temperature, is initiated by tuber apical bud meristem (TAB-meristem) sprouting characterized by apical dominance (AD). Dormancy is shortened by treatments such as bromoethane (BE), which mimics the phenotype of dormancy release in cold storage by inducing early sprouting of several buds simultaneously. We studied the mechanisms governing TAB-meristem dominance release. TAB-meristem decapitation resulted in the development of increasing numbers of axillary buds with time in storage, suggesting the need for autonomous dormancy release of each bud prior to control by the apical bud. Hallmarks of programmed cell death (PCD) were identified in the TAB-meristems during normal growth, and these were more extensive when AD was lost following either extended cold storage or BE treatment. Hallmarks included DNA fragmentation, induced gene expression of vacuolar processing enzyme1 (VPE1), and elevated VPE activity. VPE1 protein was semipurified from BE-treated apical buds, and its endogenous activity was fully inhibited by a cysteinyl aspartate-specific protease-1-specific inhibitor N-Acetyl-Tyr-Val-Ala-Asp-CHO (Ac-YVAD-CHO). Transmission electron microscopy further revealed PCD-related structural alterations in the TAB-meristem of BE-treated tubers: a knob-like body in the vacuole, development of cytoplasmic vesicles, and budding-like nuclear segmentations. Treatment of tubers with BE and then VPE inhibitor induced faster growth and recovered AD in detached and nondetached apical buds, respectively. We hypothesize that PCD occurrence is associated with the weakening of tuber AD, allowing early sprouting of mature lateral buds.
authors.affiliation: Department of Postharvest Science, The Volcani Center, Agricultural Research Organization, Bet-Dagan 50250, Israel.
authors.forename: Paula
authors.initials: P
authors.lastname: Teper-Bamnolker
authors.forename: Yossi
authors.initials: Y
authors.lastname: Buskila
authors.forename: Yael
authors.initials: Y
authors.lastname: Lopesco
authors.forename: Shifra
authors.initials: S
authors.lastname: Ben-Dor
authors.forename: Inbal
authors.initials: I
authors.lastname: Saad
authors.forename: Vered
authors.initials: V
authors.lastname: Holdengreber
authors.forename: Eduard
authors.initials: E
authors.lastname: Belausov
authors.forename: Hanita
authors.initials: H
authors.lastname: Zemach
authors.forename: Naomi
authors.initials: N
authors.lastname: Ori
authors.forename: Amnon
authors.initials: A
authors.lastname: Lers
authors.forename: Dani
authors.initials: D
authors.lastname: Eshel
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D053144:Cell Nucleus Shape / Q000187:drug effects; D003080:Cold Temperature; D053938:DNA Fragmentation / Q000187:drug effects; D035264:Flowers / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D006842:Hydrocarbons, Brominated / Q000494:pharmacology; D018519:Meristem / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D035281:Plant Tubers / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development* / Q000648:ultrastructure; D011309:Preservation, Biological; D011198:Solanum tuberosum / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development* / Q000648:ultrastructure
chemical_list: D006842:Hydrocarbons, Brominated; D009842:Oligopeptides; D010940:Plant Proteins; C096429:L 709049; C037311:bromoethane