Regulation of the gravitropic response and ethylene biosynthesis in gravistimulated snapdragon spikes by calcium chelators and ethylene inhibitors.
Philosoph-Hadas, S.; Meir, S.; Rosenberger, I.; Halevy, A. H.;
Plant Physiology Year: 1996 Vol: 110 Issue: 1 Pages: 301-310 Ref: 42 ref.
1996
บทคัดย่อ
The possible involvement of Ca2+ as a second messenger in Antirrhinum majus shoot gravitropism, as well as the role of ethylene in this bending response, were analysed using cv. Axium in terms of stem curvature and gravity-induced asymmetric ethylene production rates, ethylene-related metabolites and invertase [ beta -fructofuranosidase] activity across the stem. Application of Ca2+ chelators (EDTA, trans-1,2-cyclohexane dinitro-N,N,N',N'-tetraacetic acid, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N',-tetraacetic acid) or a Ca2+ antagonist (LaCl3) to the cut flower spikes caused a significant loss of their gravitropic response following horizontal placement. Conversely, the Ca2+ ionophore A23187 or the agonist Bay K-8644 increased gravibending. Longitudinally halved stem sections had significantly higher amounts of ethylene, 1-aminocyclopropane-1-carboxylic acid and 1-(malonylamino)cyclopropane-1-carboxylic acid than vertical controls, with the extra production arising exclusively from the lower half
of the stem. Trans-1,2-cyclohexane dinitro-N,N,N',N'-tetraacetic acid pretreatment completely abolished the gravity-induced ethylene gradient across the stem, thereby leading to a significant reduction of the curvature. Similarly, reduction of the ethylene produced in the gravistimulated stems with CoCl2 or inhibition of its action by silver thiosulfate or 2,5-norbornadiene significantly inhibited the subsequent gravibending. Silver thiosulfate and CoCl2 also abolished the gravity-induced gradient of invertase activity across the stem, which is associated with the asymmetric stem elongation. These results suggest that cytosolic Ca2+ may regulate auxin action in snapdragon spikes, manifested as increased ethylene production, which is, in turn, intimately correlated with stem bending. Therefore, both hormones seem to play significant roles in induction and progress of the gravibending of snapdragon spikes.