AGAMOUS-LIKE 17, a novel flowering promoter, acts in a FT-independent photoperiod pathway

Authors

  • Ping Han,

    1. Plant Functional Genomics Laboratory, Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, 117543, Singapore,
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  • Berenice García-Ponce,

    1. Laboratorio de Genética Molecular, Desarrollo y Evolución de Plantas, Dpto de Ecología Funcional, Instituto de Ecología, Universidad Nacional Autónoma de México, 3er Circuito Exterior S/N Junto a Jardín Botánico, México D.F. 04510, Mexico, and
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  • Gabriel Fonseca-Salazar,

    1. Laboratorio de Genética Molecular, Desarrollo y Evolución de Plantas, Dpto de Ecología Funcional, Instituto de Ecología, Universidad Nacional Autónoma de México, 3er Circuito Exterior S/N Junto a Jardín Botánico, México D.F. 04510, Mexico, and
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  • Elena R. Alvarez-Buylla,

    1. Laboratorio de Genética Molecular, Desarrollo y Evolución de Plantas, Dpto de Ecología Funcional, Instituto de Ecología, Universidad Nacional Autónoma de México, 3er Circuito Exterior S/N Junto a Jardín Botánico, México D.F. 04510, Mexico, and
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  • Hao Yu

    Corresponding author
    1. Plant Functional Genomics Laboratory, Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, 117543, Singapore,
    2. Plant Functional Genomics Group, Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore
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*(fax +65 67792486; e-mail dbsyuhao@nus.edu.sg).

Summary

The photoperiod pathway is a genetically conserved pathway that affects flowering in distantly related angiosperms. Here we report a novel flowering promoter AGAMOUS-LIKE 17 (AGL17) acting in the photoperiod pathway of Arabidopsis. AGL17 transcripts were detectable in various plant organs with the highest expression in the root. Under long-day conditions, expression of AGL17 gradually increased in the aerial part of seedlings during the floral transition. Overexpression of AGL17 caused early flowering, while loss of function of AGL17 exhibited late flowering, particularly under long days. Analysis of AGL17 expression in various flowering-time mutants showed that its transcripts were significantly reduced in the photoperiod pathway mutant co-1. Correspondingly, AGL17 expression was upregulated in transgenic plants overexpressing CONSTANS (CO) and also when CO activity was induced by light. Genetic analysis further showed that overexpression of AGL17 could partially suppress the late flowering of co-1. These results suggest that AGL17 acts to promote flowering and is positively controlled by the photoperiod pathway regulator CO. In contrast, another target of CO, FLOWERING LOCUS T (FT), did not affect AGL17 expression, and vice versa. The expression of two floral meristem identity genes LEAFY (LFY) and APETALA1 (AP1) decreased in agl17-1, while LFY and AP1 could be rapidly induced by AGL17 using a functional estradiol-inducible system. These findings indicate that AGL17 ultimately promotes flowering via regulation of LFY and AP1.

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