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Computer-assisted Video Image Analysis of Spatial Variations in Membrane-associated Ca2+ and Calmodulin during Pollen Hydration, Germination and Tip Growth in Nicotiana tabacum L.
Authors:TIRLAPUR  UDAY K; CRESTI  MAURO
Institution:Department of Environmental Biology, University of Siena Via P. A. Mattioli, 4, 1-53100 Siena, Italy
Abstract:Video images of the distributional pattern of membrane-associatedcalcium (Ca2+) and calmodulin (CaM) have been documented andanalysed during pollen hydration, germination and tip growthin Nicotiana tabacum. Digitization of fluorescence microscopeimages of chlorotetracycline (CTC) and fluphenazine (FPZ)-fluorescenceemissions reveal that there is a maximum concentration of membrane-associatedCa2+ and also CaM in the vicinity of germination apertures ofhydrated pollen. With the onset of germination relatively higheramounts of Ca2+ and CaM were found to regionalize towards theaperture through which the pollen tube would emerge Both shortand long growing pollen tubes manifest tip-to-base Ca2+ andCaM gradients which are disturbed in non-growing tubes. Tubegrowth and the Ca2+-gradient were significantly affected byvanadate and verapamil suggesting that both a vanadate-sensitiveCa2+-transport system and verapamil-sensitive Ca2+ channelsare involved in maintaining Ca2+ homeostasis during pollen germinationand tube growth. The possible interactions of Ca2+ and CaM withdifferent cytoskeletal proteins modulating organelle movementare also briefly discussed. Image analysis, calcium, calmodulin, Nicotiana tabacum L., pollen germination, pollen tube, tip growth, Ca2+-channels, Ca2+ transport ATPase
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