title: Circadian oscillatory transcriptional programs in grapevine ripening fruits.
abstract: BACKGROUND
  Temperature and solar radiation influence Vitis vinifera L. berry ripening. Both environmental conditions fluctuate cyclically on a daily period basis and the strength of this fluctuation affects grape ripening too. Additionally, a molecular circadian clock regulates daily cyclic expression in a large proportion of the plant transcriptome modulating multiple developmental processes in diverse plant organs and developmental phases. Circadian cycling of fruit transcriptomes has not been characterized in detail despite their putative relevance in the final composition of the fruit. Thus, in this study, gene expression throughout 24 h periods in pre-ripe berries of Tempranillo and Verdejo grapevine cultivars was followed to determine whether different ripening transcriptional programs are activated during certain times of day in different grape tissues and genotypes.
  
  
  RESULTS
  Microarray analyses identified oscillatory transcriptional profiles following circadian variations in the photocycle and the thermocycle. A higher number of expression oscillating transcripts were detected in samples carrying exocarp tissue including biotic stress-responsive transcripts activated around dawn. Thermotolerance-like responses and regulation of circadian clock-related genes were observed in all studied samples. Indeed, homologs of core clock genes were identified in the grapevine genome and, among them, VvREVEILLE1 (VvRVE1), showed a consistent circadian expression rhythm in every grape berry tissue analysed. Light signalling components and terpenoid biosynthetic transcripts were specifically induced during the daytime in Verdejo, a cultivar bearing white-skinned and aromatic berries, whereas transcripts involved in phenylpropanoid biosynthesis were more prominently regulated in Tempranillo, a cultivar bearing black-skinned berries.
  
  
  CONCLUSIONS
  The transcriptome of ripening fruits varies in response to daily environmental changes, which might partially be under the control of circadian clock components. Certain cultivar and berry tissue features could rely on specific circadian oscillatory expression profiles. These findings may help to a better understanding of the progress of berry ripening in short term time scales.
authors.affiliation: Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas-Universidad de La Rioja-Gobierno de La Rioja, Madre de Dios 51, 26006 Logroño, Spain. pablo.carbonell@icvv.es.
authors.forename: Pablo
authors.initials: P
authors.lastname: Carbonell-Bejerano
authors.forename: Virginia
authors.initials: V
authors.lastname: Rodríguez
authors.forename: Carolina
authors.initials: C
authors.lastname: Royo
authors.forename: Silvia
authors.initials: S
authors.lastname: Hernáiz
authors.forename: Luis Carlos
authors.initials: LC
authors.lastname: Moro-González
authors.forename: Montserrat
authors.initials: M
authors.lastname: Torres-Viñals
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Martínez-Zapater
mesh_terms: D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D005638:Fruit / Q000378:metabolism* / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D027843:Vitis / Q000378:metabolism* / Q000502:physiology*