Reactions and change of forisome position in <i>Vicia faba</i> (A-E) and forisome location in <i>Phaseolus vulgaris</i> sieve elements (F-O) in response to remote heating (forisomes are marked by asterisks).

<p>A. <i>Vicia faba</i> forisome (upstream position 1). B-E <i>Vicia faba</i> forisome (downstream position, position1). B. Initial position at an angle of about 10° to the longitudinal axis, C. Dispersion in response to a remote heat shock, D. Re-condensation, 4 min after the stimulus, position parallel to the longitudinal axis, E. 5 min after stimulus, position at an angle of about 10° to the longitudinal axis. F. <i>Phaseolus vulgaris</i> forisome (upstream position). G-I Long-distance ovement of a non-primed condensed Phaseolus vulgaris forisome from the downstream position 1 to the upstream position 4, J-L Short-distance movement of a non-primed condensed <i>Phaseolus vulgaris</i> forisome from the downstream position 1 (J.), via the central position 4 (K) back to the original downstream position 1 (L). M-O No position change of a dispersed <i>Phaseolus vulgaris</i> forisome. Direction of flow in G to O from right to left.</p

Forisome reactivity in response to remote burning of intact non-primed <i>Phaseolus vulgaris</i> plants as related to its location.

<p>“Reaction” includes both dispersion or movement.</p

A-C Dispersion and re-condensation of a forisome in a LatA pretreated non-primed <i>Phaseolus vulgaris</i>plant in response to a remote heat stimulus. D. Relationship between dispersion and re-condensation times.

<p>The stippled line indicates the relationship between dispersion and re-condensation time.</p

A. Average acropetal and subsequent basipetal movement velocities of originally downstream located condensed <i>Phaseolus vulgaris</i> forisomes after a distant heat stimulus in non-primed plants. B. Response lag times of location changes of forisomes in <i>Phaseolus</i> vulgaris and the distances of movement.

<p>The stippled line indicates the relationship between dispersion and re-condensation time.</p

Forisome positions at diverse sieve-element locations in <i>Vicia faba</i> (A-D) and <i>Phaseolus vulgaris</i> (E-H).

<p>A. and E. basal (downstream); B. and F. central; C. and G. apical (upstream). D. and H. Percentage of forisomes at each location and position. The black areas indicate forisomes in contact with the sieve-element side facing the companion cell. Different letters indicate significant differences between the positions of forisomes.</p

Reactivity of basal forisomes pretreated with LatA in response to remote burning of intact non-primed <i>Phaseolus vulgaris</i> plants as related to its position, without prior priming.

<p>“Reaction” includes both dispersion and movement.</p

Similar Intracellular Location and Stimulus Reactivity, but Differential Mobility of Tailless (<i>Vicia faba)</i> and Tailed Forisomes (<i>Phaseolus vulgaris</i>) in Intact Sieve Tubes

<div><p>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 <i>Vicia faba</i>) and tailed (in <i>Phaseolus vulgaris)</i> 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 (<i>Phaseolus</i>) and broadbean (<i>Vicia</i>). 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.</p></div

Absolute numbers and percentage of forisome locations (basal, central, apical) in sieve elements of A. <i>Vicia faba</i> and B. <i>Phaseolus vulgaris</i>.

<p>Different letters indicate significant differences (p < 0.05) between locations and plant species.</p

Reactivity of basal forisomes in response to remote burning of intact <i>Phaseolus vulgaris</i> plants as related to its position.

<p>“Reaction” includes both dispersion and movement.</p

Forisome locations and positions inside sieve elements.

<p>A. Basal (downstream), central and apical (upstream) locations. B. Position1, Forisome tips in contact with the plasma membrane lining the sieve plate and the parietal plasma membrane, position 2 one tip in contact with the plasma membrane lining the sieve plate, the other is free-floating in the sieve-element lumen, position 3 one tip in contact with the parietal plasma membrane, position, the other is free-floating in the sieve-element lumen, position 4 no apparent tip contacts.</p