title: Similar Intracellular Location and Stimulus Reactivity, but Differential Mobility of Tailless (Vicia faba) and Tailed Forisomes (Phaseolus vulgaris) in Intact Sieve Tubes.
abstract: Sieve elements of legumes contain forisomes-fusiform protein bodies that are responsible for sieve-tube occlusion in response to damage or wound signals. Earlier work described the existence of tailless and tailed forisomes. This study intended to quantify and compare location and position of tailless (in Vicia faba) and tailed (in Phaseolus vulgaris) forisomes inside sieve elements and to assess their reactivity and potential mobility in response to a remote stimulus. Location (distribution within sieve elements) and position (forisome tip contacts) of more than altogether 2000 forisomes were screened in 500 intact plants by laser scanning confocal microscopy in the transmission mode. Furthermore, we studied the dispersion of forisomes at different locations in different positions and their positional behaviour in response to distant heat shocks. Forisome distribution turned out to be species-specific, whereas forisome positions at various locations were largely similar in bushbean (Phaseolus) and broadbean (Vicia). In general, the tailless forisomes had higher dispersion rates in response to heat shocks than the tailed forisomes and forisomes at the downstream (basal) end dispersed more frequently than those at the upstream end (apical). In contrast to the tailless forisomes that only oscillate in response to heat shocks, downstream-located tailed forisomes can cover considerable distances within sieve elements. This displacement was prevented by gentle rubbing of the leaf (priming) before the heat shock. Movement of these forisomes was also prohibited by Latrunculin A, an inhibitor of actin polymerization. The apparently active mobility of tailed forisomes gives credence to the idea that at least the latter forisomes are not free-floating, but connected to other sieve-element structures.
authors.affiliation: Institute of General Botany and Plant Physiology, Friedrich-Schiller-University, Jena, Germany.
authors.forename: Alexandra C U
authors.initials: AC
authors.lastname: Furch
authors.affiliation: Research Centre for BioSystems, Land Use and Nutrition, Institute of Phytopathology and Applied Zoology, Justus-Liebig University, Giessen, Germany.
authors.forename: Stefanie V
authors.initials: SV
authors.lastname: Buxa
authors.affiliation: Plant Cell Biology Research Group, Institute of General Botany, Justus-Liebig University, Giessen, Germany.
authors.forename: Aart J E
authors.initials: AJ
authors.lastname: van Bel
mesh_terms: D001686:Biological Phenomena / Q000502:physiology; D003593:Cytoplasm / Q000378:metabolism / Q000502:physiology; D018613:Microscopy, Confocal / Q000379:methods; D027805:Phaseolus / Q000378:metabolism / Q000502:physiology*; D052585:Phloem / Q000378:metabolism / Q000502:physiology; D010829:Physiological Phenomena / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism; D031307:Vicia faba / Q000378:metabolism / Q000502:physiology*
chemical_list: D010940:Plant Proteins