Involvement of signal transduction pathway components in photoperiodic flower induction in Pharbitis nil |
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Authors: | Amihud Borochov Hanna Spiegelstein Abraham H. Halevy |
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Affiliation: | The Kennedy Leigh Centre for Horticulture. The Hebrew Univ. of Jerusalem, P.O. Box 12, Rehovot, 76100 Israel. |
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Abstract: | The possible participation of several major components of the signal transduction pathway in photoperiodic flower induction was examined in Pharbitis cotyledons. Exogenous applications of GTP-γ-S (1–10 μ M ) or of the phorbol ester, phorbol 12-myristate-13-acetate (PMA, 0.1–5.0 μ M ) to Pharbitis plants held under a marginal inductive period (11.5 h dark) significantly increased their flowering response. Membrane lipid fluidity, GTP-binding and protein kinase activity were increased following a single flowering-inducing dark period of 16 h; however, a light-break of 10 min that abolished flower induction failed to reverse the dark-induced increase in these processes. Photo-inductive dark conditions significantly increased the content of diacylglycerol (DAG) and phosphoinositides in the cotyledon membranes, together with the activities of their kinases, and a light break decreased them to control levels and below. In addition, a single spraying with GTP-γ-S or PMA at 1 μ M significantly increased both the lipid content and the kinase activities. These compounds also enhanced the kinase activities in vitro. It is concluded that DAG and phosphoinositide metabolism play a role in the linking of the photoperiodic induction of the phytochrome with the flowering response in Pharbitis nil . |
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Keywords: | Flower induction lipid kinases membranes Pharbitis nil phosphorylation photoperiod signal transduction |
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