Fruit load modulates flowering-related gene expression in buds of alternate-bearing ‘Moncada’ mandarin |
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Authors: | Natalia Mu?oz-Fambuena Carlos Mesejo M Carmen González-Mas Eduardo Primo-Millo Manuel Agustí Domingo J Iglesias |
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Institution: | 1.Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, E-46022 Valencia, Spain;2.Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias, E-46113 Moncada, Valencia, Spain |
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Abstract: | Background and AimsGene determination of flowering is the result of complex interactions involving both promoters and inhibitors. In this study, the expression of flowering-related genes at the meristem level in alternate-bearing citrus trees is analysed, together with the interplay between buds and leaves in the determination of flowering.MethodsFirst defruiting experiments were performed to manipulate blossoming intensity in ‘Moncada’ mandarin, Citrus clementina. Further defoliation was performed to elucidate the role leaves play in the flowering process. In both cases, the activity of flowering-related genes was investigated at the flower induction (November) and differentiation (February) stages.Key ResultsStudy of the expression pattern of flowering-genes in buds from on (fully loaded) and off (without fruits) trees revealed that homologues of FLOWERING LOCUS T (CiFT), TWIN SISTER OF FT (TSF), APETALA1 (CsAP1) and LEAFY (CsLFY) were negatively affected by fruit load. CiFT and TSF activities showed a marked increase in buds from off trees through the study period (ten-fold in November). By contrast, expression of the homologues of the flowering inhibitors of TERMINAL FLOWER 1 (CsTFL), TERMINAL FLOWER 2 (TFL2) and FLOWERING LOCUS C (FLC) was generally lower in off trees. Regarding floral identity genes, the increase in CsAP1 expression in off trees was much greater in buds than in leaves, and significant variations in CsLFY expression (approx. 20 %) were found only in February. Defoliation experiments further revealed that the absence of leaves completely abolished blossoming and severely affected the expression of most of the flowering-related genes, particularly decreasing the activity of floral promoters and of CsAP1 at the induction stage.ConclusionsThese results suggest that the presence of fruit affects flowering by greatly altering gene-expression not only at the leaf but also at the meristem level. Although leaves are required for flowering to occur, their absence strongly affects the activity of floral promoters and identity genes. |
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Keywords: | Alternate bearing AP1 citrus flowering FT FD FLC LFY SOC1 TFL1 TFL2 TSF |
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