EnvReg213-page15 - FT is synthesized in phloem companion...

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Plant Environmental Regulators - 15 The Mysterious Flowering “Hormone” and Flowering Genetics Related to the discussion of flowering, and of some interest, is the actual flower stimulus. It was long thought there must be a flowering hormone. It was even given a name, florigen, but identification of such a hormone was elusive. It had been shown that if two plants were connected to each other, and one was kept in the dark, both flowered if the one in the light got the correct photoperiodic treatment, which supported evidence of some chemical translocation. Both RNA and proteins travel symplastic routes through plasmodesmata within the plant, so it was reasonable to conclude that chemicals to induce flowering can be translocated. Research with Arabidopsis ultimately demonstrated that three genes control the initiation of flowering. Flowering Locus T (FT) is activated in leaves when conditions favor flowering, and codes for the protein, florigen.
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Unformatted text preview: FT is synthesized in phloem companion cells, moves into sieve tubes and travels to the apical meristem to initiate transition to a flowering shoot. FT expressed in high concentration in apical meristems can induce flowering even when conditions are not favorable. • Constans (CO) codes for the transcription factor than activates the synthesis of Flowering Locus T. CO functions in the leaf. Over expression of CO in apical meristems has no effect. CO requires an appropriate photoperiod regimen to remain stable long enough to activate FT synthesis. • Flowering Locus D (FD) codes for a protein,Apetala 1, that binds to FT in the apical meristem. The FD and FT complex activate transcription factors for meristem flower part genes (discussed in pattern identity genes in Biology 211 and in our discussion of flowering plant reproduction and development.)...
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