Rapid cooling triggers forisome dispersion just before phloem transport stops

Thorpe, M. R.; Furch, Alexandra C. U.; Minchin, P. E. H.; Föller, Jens; Bel, Aart J. E. van; Hafke, Jens B.

doi:10.1111/j.1365-3040.2009.02079.x

Cited by 38 publications

(26 citation statements)

References 61 publications

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“…Initially, we observed intact sieve tubes for several hours by epifluorescence and confocal microscopy without any indication of dynamic behavior of SEOR1 bundles and agglomerations. Then, we tested different injury stimuli that are known to trigger the forisome reaction, such as local mechanical injury, distant burning of leaf tips, and local cold shocks (Furch et al, 2007;Thorpe et al, 2010). None of the treatments triggered any immediate reaction.…”

Section: Seor1 Functionmentioning

confidence: 99%

Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation

et al. 2011

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Since the first ultrastructural investigations of sieve tubes in the early 1960s, their structure has been a matter of debate. Because sieve tube structure defines frictional interactions in the tube system, the presence of P protein obstructions shown in many transmission electron micrographs led to a discussion about the mode of phloem transport. At present, it is generally agreed that P protein agglomerations are preparation artifacts due to injury, the lumen of sieve tubes is free of obstructions, and phloem flow is driven by an osmotically generated pressure differential according to Mü nch's classical hypothesis. Here, we show that the phloem contains a distinctive network of protein filaments. Stable transgenic lines expressing Arabidopsis thaliana Sieve-Element-Occlusion-Related1 (SEOR1)-yellow fluorescent protein fusions show that At SEOR1 meshworks at the margins and clots in the lumen are a general feature of living sieve tubes. Live imaging of phloem flow and flow velocity measurements in individual tubes indicate that At SEOR1 agglomerations do not markedly affect or alter flow. A transmission electron microscopy preparation protocol has been generated showing sieve tube ultrastructure of unprecedented quality. A reconstruction of sieve tube ultrastructure served as basis for tube resistance calculations. The impact of agglomerations on phloem flow is discussed.

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Section: Seor1 Functionmentioning

confidence: 99%

Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation

et al. 2011

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“…To determine whether roots effectively compete with defense-induced primary and secondary metabolites for carbon resources, root chilling treatments were used to disrupt carbon flow between above-and belowground tissues. The inhibition of phloem transport by chilling roots has been particularly well investigated (Geiger, 1969;Minchin et al, , 1994Poiré et al, 2010;Thorpe et al, 2010) and can be accomplished with minor drops in temperature . In our experiments, individual plants were seated inside an epoxy-sealed pot affixed in an ice water bath (0°C; Supplemental Fig.…”

Section: Root Chilling Treatmentmentioning

confidence: 99%

Temporal Changes in Allocation and Partitioning of New Carbon as 11C Elicited by Simulated Herbivory Suggest that Roots Shape Aboveground Responses in Arabidopsis

et al. 2012

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Using the short-lived isotope 11C (t1/2 = 20.4 min) as 11CO2, we captured temporal changes in whole-plant carbon movement and partitioning of recently fixed carbon into primary and secondary metabolites in a time course (2, 6, and 24 h) following simulated herbivory with the well-known defense elicitor methyl jasmonate (MeJA) to young leaves of Arabidopsis (Arabidopsis thaliana). Both 11CO2 fixation and 11C-photosynthate export from the labeled source leaf increased rapidly (2 h) following MeJA treatment relative to controls, with preferential allocation of radiolabeled resources belowground. At the same time, 11C-photosynthate remaining in the aboveground sink tissues showed preferential allocation to MeJA-treated, young leaves, where it was incorporated into 11C-cinnamic acid. By 24 h, resource allocation toward roots returned to control levels, while allocation to the young leaves increased. This corresponded to an increase in invertase activity and the accumulation of phenolic compounds, particularly anthocyanins, in young leaves. Induction of phenolics was suppressed in sucrose transporter mutant plants (suc2-1), indicating that this phenomenon may be controlled, in part, by phloem loading at source leaves. However, when plant roots were chilled to 5°C to disrupt carbon flow between above- and belowground tissues, source leaves failed to allocate resources belowground or toward damaged leaves following wounding and MeJA treatment to young leaves, suggesting that roots may play an integral role in controlling how plants respond defensively aboveground.

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“…Considerable evidence indicates that low temperatures slow phloem transport and increase foliar sugar concentrations (e.g., Keskitalo et al 2005;Thorpe et al 2010). Other studies have repeatedly linked sugar enhancement to anthocyanin production (Hiratsuka et al 2001;Hara et al 2003), including among woody species under field conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Likewise, drought conditions (Gebre and Tschaplinski 2002), as well as pathogen infection (Bolouri Moghaddam and Van den Ende 2012), can also result in an accumulation of foliar soluble sugars and anthocyanins. In particular, it is well established that low-temperature exposure slows and can even halt phloem transport, thereby leading to foliar sugar buildups (e.g., Keskitalo et al 2005;Thorpe et al 2010). Mechanical disruption of the phloem can increase anthocyanin expression in a range of plant forms (e.g., Hughes et al 2005), and previous research showed that girdling sugar maple (Acer saccharum Marsh.)…”

Section: Introductionmentioning

confidence: 99%

Experimental branch cooling increases foliar sugar and anthocyanin concentrations in sugar maple at the end of the growing season

et al. 2017

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Autumnal leaf anthocyanin expression is enhanced following exposure to a variety of environmental stresses and may represent an adaptive benefit of protecting leaves from those stresses, thereby allowing for prolonged sugar and nutrient resorption. Past work has shown that experimentally induced sugar accumulations following branch girdling triggers anthocyanin biosynthesis. We hypothesized that reduced phloem transport at low autumnal temperatures may increase leaf sugar concentrations that stimulate anthocyanin production, resulting in enhanced tree-and landscape-scale color change. We used refrigerant-filled tubing to cool individual branches in a mature sugar maple (Acer saccharum Marsh.) tree to test whether phloem cooling would trigger foliar sugar accumulations and enhance anthocyanin biosynthesis. Cooling increased foliar sucrose, glucose, and fructose concentrations 2-to nearly 10-fold (depending on the specific sugar and sampling date) relative to controls and increased anthocyanin concentrations by approximately the same amount. Correlation analyses indicated a strong and steady positive relationship between anthocyanin and sugar concentrations, which was consistent with a mechanistic link between cooling-induced changes in these constituents. Tested here at the branch level, we propose that low temperature induced reductions in phloem transport may be responsible for increases in foliar sugars that trigger anthocyanin displays at grander scales.Key words: fall leaf color, low temperature, sucrose, glucose, fructose, Acer saccharum.Résumé : L'apparition des anthocyanines dans les feuilles à l'automne est amplifiée par l'exposition à divers stress environnementaux et pourrait représenter un avantage adaptatif en protégeant les feuilles contre ces stress; ce qui permettrait par conséquent de prolonger la résorption des sucres et des nutriments. Des travaux antérieurs ont montré que l'accumulation expérimentalement induite des sucres après avoir annelé des branches déclenche la biosynthèse des anthocyanines. Nous avons émis l'hypothèse que le ralentissement du transport dans le phloème causé par les températures basses à l'automne pourrait augmenter la concentration des sucres; ce qui stimulerait la production des anthocyanines et entraînerait un changement de couleur plus intense à l'échelle de l'arbre et du paysage. Nous avons utilisé une tubulure contenant un fluide frigorigène pour refroidir des branches dans un érable à sucre (Acer saccharum Marsh.) mature afin de tester si le refroidissement du phloème déclencherait une accumulation des sucres dans les feuilles et augmenterait la biosynthèse des anthocyanines. Le refroidissement a augmenté la concentration de sucrose, de glucose et de fructose dans les feuilles de 2 à près de 10 fois (dépendemment de la nature du sucre et de la date d'échantillonnage) comparativement aux branches témoins et a aussi augmenté la concentration des anthocyanines dans environ la même proportion. Les analyses de corrélation montrent qu'il y a une relation posit...

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Rapid cooling triggers forisome dispersion just before phloem transport stops

Cited by 38 publications

References 61 publications

Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation

Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation

Temporal Changes in Allocation and Partitioning of New Carbon as 11C Elicited by Simulated Herbivory Suggest that Roots Shape Aboveground Responses in Arabidopsis

Experimental branch cooling increases foliar sugar and anthocyanin concentrations in sugar maple at the end of the growing season

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