Auxin-induced delay of abscission: The involvement of calcium ions and protein phosphorylation in bean explants |
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Authors: | B. W. Poovaiah M. Friedmann A. S. N. Reddy J. K. Rhee |
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Affiliation: | Lab. of Plant Molecular Biol. and Physiol., Dept of Horticulture and Landscape Architecture, Washington State Univ., Pullman, WA 99164–6414, USA. |
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Abstract: | Treatment with Ca2+ channel blockers such as lanthanum chloride and verapamil promoted abscission in pulvinar explants of bean ( Phaseolus vulgaris L. ev. Pirate). In addition, auxin-induced delay of abscission was markedly reduced in the presence of Ca2+ channel blockers. In vitro phosphorylation studies were performed using membrane preparations (130000 g pellet) from freshly excised as well as auxintreated and control (minus auxin) pulvinar sections. Auxin-treated sections showed a 66 kDa phosphoprotein as well as Ca2+ -dependent phosphorylation that were not observed in control explants. Coomassie blue stammg of soluble proteins (130000 g supernatent) separated on SDS-PAGE revealed the presence of 62. 55 and 47 kDa polypeptides only in the freshly excised pulvini. However. no distinct changes were observed in soluble protein profile between auxin-treated and control explants. When soluble proteins were phosphorylated in vitro, Ca2+ promoted the phosphorylation of 92, 55. 40 and I7 kDa polypeptides only in freshly excised pulvmi. Ca2+-dependent phosphorylation of soluble proteins was not observed in either the control or auxin-treated explants. In addition. in vivo phosphorylation studies were performed using freshly excised. auxrn-treated and control explants. Freshly excused segments and auxin-treated ex-plants showed similar phosphoproteins, which were different from those observed mcontrol. |
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Keywords: | Ahscisston auxin calcium garden bean lanthanum chloride naphthaleneacettcacid Phaseolus vulgarrs proten phosphorylation verapamil |
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