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Remote-controlled stop of phloem mass flow by biphasic occlusion in Cucurbita maxima.

Furch AC, Zimmermann MR, Will T, Hafke JB, van Bel AJ - J. Exp. Bot. (2010)

Bottom Line: A few minutes after passage of the first EPW peak, sieve tubes gradually became occluded by callose, with maximum synthesis occurring approximately 10 min after burning.This obstruction of mass flow was inferred from the halt of carboxyfluorescein movement in sieve tubes and intensified secretion of aqueous saliva by feeding aphids.Mass flow resumed 30-40 min after burning, as demonstrated by carboxyfluorescein movement and aphid activities.

View Article: PubMed Central - PubMed

Affiliation: Plant Cell Biology Research Group, Institute of General Botany, Justus-Liebig-University, Senckenbergstrasse 17, D-35390 Giessen, Germany. Alexandra.C.Furch@bot1.bio.uni-giessen.de

ABSTRACT
The relationships between damage-induced electropotential waves (EPWs), sieve tube occlusion, and stop of mass flow were investigated in intact Cucurbita maxima plants. After burning leaf tips, EPWs propagating along the phloem of the main vein were recorded by extra- and intracellular microelectrodes. The respective EPW profiles (a steep hyperpolarization/depolarization peak followed by a prolonged hyperpolarization/depolarization) probably reflect merged action and variation potentials. A few minutes after passage of the first EPW peak, sieve tubes gradually became occluded by callose, with maximum synthesis occurring approximately 10 min after burning. Early stop of mass flow, well before completion of callose deposition, pointed to an occlusion mechanism preceding callose deposition. This obstruction of mass flow was inferred from the halt of carboxyfluorescein movement in sieve tubes and intensified secretion of aqueous saliva by feeding aphids. The early occlusion is probably due to proteins, as indicated by a dramatic drop in soluble sieve element proteins and a simultaneous coagulation of sieve element proteins shortly after the burning stimulus. Mass flow resumed 30-40 min after burning, as demonstrated by carboxyfluorescein movement and aphid activities. Stop of mass flow by Ca(2+)-dependent occlusion mechanisms is attributed to Ca(2+) influx during EPW passage; the reversibility of the occlusion is explained by removal of Ca(2+) ions.

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Related in: MedlinePlus

(A) 1-D SDS–PAGE of Cucurbita maxima phloem sap proteins stained with Coomassie blue (n=7). Lane 1, marker proteins; lane 2, protein bands of 0.5 μl of phloem sap collected from an untreated plant; lane 3, protein bands of 0.5 μl of phloem sap collected 5 min after burning the leaf tip/main vein at 9 cm distance. Note the changes of staining intensity of the major protein bands for PP1 and the PP2-dimer. (B) Comparison of the pixel intensity of the bands in lane 2 (grey curve) and lane 3 (black curve) by use of Quantity One 1-D Analysis Software.
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fig6: (A) 1-D SDS–PAGE of Cucurbita maxima phloem sap proteins stained with Coomassie blue (n=7). Lane 1, marker proteins; lane 2, protein bands of 0.5 μl of phloem sap collected from an untreated plant; lane 3, protein bands of 0.5 μl of phloem sap collected 5 min after burning the leaf tip/main vein at 9 cm distance. Note the changes of staining intensity of the major protein bands for PP1 and the PP2-dimer. (B) Comparison of the pixel intensity of the bands in lane 2 (grey curve) and lane 3 (black curve) by use of Quantity One 1-D Analysis Software.

Mentions: The previous results (Fig. 3, 4) suggest ready occlusion of SPs at the time that callose deposition has hardly started. In analogy to the events in V. faba (Furch et al., 2007, 2009), proteins may be engaged in sieve tube occlusion. Therefore, the response of SE proteins to burning the leaf tip/major vein at a distance of 9 cm was observed using sulphorhodamine 101 (Fig. 5) and separation by 1-D SDS-PAGE (Fig. 6). Twenty minutes prior to burning, 10 μM sulphorhodamine 101 (cf. Peters et al., 2010), which preferentially associates with membranes, was applied onto the observation window. From 5 min after burning onwards, a cloud of fluorescence was observed at the SPs (Fig. 5B, C) indicative of protein clogging. It was technically impossible to further shorten the period between burning and observation.


Remote-controlled stop of phloem mass flow by biphasic occlusion in Cucurbita maxima.

Furch AC, Zimmermann MR, Will T, Hafke JB, van Bel AJ - J. Exp. Bot. (2010)

(A) 1-D SDS–PAGE of Cucurbita maxima phloem sap proteins stained with Coomassie blue (n=7). Lane 1, marker proteins; lane 2, protein bands of 0.5 μl of phloem sap collected from an untreated plant; lane 3, protein bands of 0.5 μl of phloem sap collected 5 min after burning the leaf tip/main vein at 9 cm distance. Note the changes of staining intensity of the major protein bands for PP1 and the PP2-dimer. (B) Comparison of the pixel intensity of the bands in lane 2 (grey curve) and lane 3 (black curve) by use of Quantity One 1-D Analysis Software.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2921205&req=5

fig6: (A) 1-D SDS–PAGE of Cucurbita maxima phloem sap proteins stained with Coomassie blue (n=7). Lane 1, marker proteins; lane 2, protein bands of 0.5 μl of phloem sap collected from an untreated plant; lane 3, protein bands of 0.5 μl of phloem sap collected 5 min after burning the leaf tip/main vein at 9 cm distance. Note the changes of staining intensity of the major protein bands for PP1 and the PP2-dimer. (B) Comparison of the pixel intensity of the bands in lane 2 (grey curve) and lane 3 (black curve) by use of Quantity One 1-D Analysis Software.
Mentions: The previous results (Fig. 3, 4) suggest ready occlusion of SPs at the time that callose deposition has hardly started. In analogy to the events in V. faba (Furch et al., 2007, 2009), proteins may be engaged in sieve tube occlusion. Therefore, the response of SE proteins to burning the leaf tip/major vein at a distance of 9 cm was observed using sulphorhodamine 101 (Fig. 5) and separation by 1-D SDS-PAGE (Fig. 6). Twenty minutes prior to burning, 10 μM sulphorhodamine 101 (cf. Peters et al., 2010), which preferentially associates with membranes, was applied onto the observation window. From 5 min after burning onwards, a cloud of fluorescence was observed at the SPs (Fig. 5B, C) indicative of protein clogging. It was technically impossible to further shorten the period between burning and observation.

Bottom Line: A few minutes after passage of the first EPW peak, sieve tubes gradually became occluded by callose, with maximum synthesis occurring approximately 10 min after burning.This obstruction of mass flow was inferred from the halt of carboxyfluorescein movement in sieve tubes and intensified secretion of aqueous saliva by feeding aphids.Mass flow resumed 30-40 min after burning, as demonstrated by carboxyfluorescein movement and aphid activities.

View Article: PubMed Central - PubMed

Affiliation: Plant Cell Biology Research Group, Institute of General Botany, Justus-Liebig-University, Senckenbergstrasse 17, D-35390 Giessen, Germany. Alexandra.C.Furch@bot1.bio.uni-giessen.de

ABSTRACT
The relationships between damage-induced electropotential waves (EPWs), sieve tube occlusion, and stop of mass flow were investigated in intact Cucurbita maxima plants. After burning leaf tips, EPWs propagating along the phloem of the main vein were recorded by extra- and intracellular microelectrodes. The respective EPW profiles (a steep hyperpolarization/depolarization peak followed by a prolonged hyperpolarization/depolarization) probably reflect merged action and variation potentials. A few minutes after passage of the first EPW peak, sieve tubes gradually became occluded by callose, with maximum synthesis occurring approximately 10 min after burning. Early stop of mass flow, well before completion of callose deposition, pointed to an occlusion mechanism preceding callose deposition. This obstruction of mass flow was inferred from the halt of carboxyfluorescein movement in sieve tubes and intensified secretion of aqueous saliva by feeding aphids. The early occlusion is probably due to proteins, as indicated by a dramatic drop in soluble sieve element proteins and a simultaneous coagulation of sieve element proteins shortly after the burning stimulus. Mass flow resumed 30-40 min after burning, as demonstrated by carboxyfluorescein movement and aphid activities. Stop of mass flow by Ca(2+)-dependent occlusion mechanisms is attributed to Ca(2+) influx during EPW passage; the reversibility of the occlusion is explained by removal of Ca(2+) ions.

Show MeSH
Related in: MedlinePlus