Pathways for inflorescence and floral induction in Antirrhinum.
The presentation of flowers on a modified stem, the inflorescence, requires the integration of several aspects of meristem behaviour. In Antirrhinum, the inflorescence can be distinguished by its flowers, hairy stem, modified leaves, short internodes and spiral phyllotaxy. We show, by a combination of physiological, genetical and morphological analysis, that the various aspects of the inflorescence are controlled by three pathways. The first pathway, depends on expression of the floricaula gene, and is rapidly and discretely induced by exposure to long daylength. Activation of this pathway occurs in very young axillary meristems, resulting in a floral identity. In addition, the length of subtending leaves and hairiness of the stem are partially modified. The second pathway affects leaf size, internode length, and stem hairiness, but does not confer floral meristem identity. This pathway is induced by long daylength, but not as rapidly or discretely as the floricaula-dependent pathway. The third pathway controls the switch in phyllotaxy from decussate to spiral and is activated independently of daylength. The coordination of these three programmes ensures that apical and axillary meristem behaviour is integrated.
Bradley
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D
Genetics Department, John Innes Centre, Norwich, UK.
Vincent
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C
Carpenter
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R
Coen
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E
D001483:Base Sequence; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D018519:Meristem / Q000033:anatomy & histology / Q000254:growth & development*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D017440:Photoperiod; D063245:Plant Development; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics; D018547:Plant Stems / Q000033:anatomy & histology / Q000254:growth & development; D010944:Plants / Q000235:genetics / Q000528:radiation effects; D016133:Polymerase Chain Reaction
C083654:FLO protein, Antirrhinum majus; D010940:Plant Proteins