Plasmodesmata and Phloem: Conduits for Local and Long‐distance Signaling

Gilbertson, R. L.; Rojas, María R.; Lucas, William J.

doi:10.1002/9780470988572.ch8

Cited by 5 publications

(3 citation statements)

References 81 publications

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“…Gilbertson et al, 2005;van Bel and Ehlers, 2005). In the absence of clear-cut information on the nature of systemic signals, broad-spectrum analyses of sieve-tube compounds after induction of systemic signalling events may assist to unravel systemic networks.…”

Section: Discussionmentioning

confidence: 99%

“…The time-consuming procedure urges one to focus on likely candidates on the risk of missing the actual signals. We chose proteins as the first targets, since they occur in larger amounts in the phloem sap (Hayashi et al, 2000), are translocated over long distances (Fisher et al, 1992;Golecki et al, 1998) and are therefore suspected to operate in long-distance signalling (Gilbertson et al, 2005). For instance, the putative lipid transport protein DIR1 is essential for induction of an SAR (Maldonado et al, 2002).…”

Section: Collection Of Phloem-sap Samples For Detection Of Systemic Smentioning

confidence: 99%

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A combinatory approach for analysis of protein sets in barley sieve-tube samples using EDTA-facilitated exudation and aphid stylectomy

Gaupels

Knauer

Bel

2008

Journal of Plant Physiology

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Section: Discussionmentioning

confidence: 99%

Section: Collection Of Phloem-sap Samples For Detection Of Systemic Smentioning

confidence: 99%

A combinatory approach for analysis of protein sets in barley sieve-tube samples using EDTA-facilitated exudation and aphid stylectomy

Gaupels

Knauer

Bel

2008

Journal of Plant Physiology

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“…Gilbertson discusses such movement. 29 The movement of the sucrose is enhanced because it is now pulled though the pore by virtue of its attachment to the proton. This is in contrast to a purely hydraulic passage.…”

Section: Significance Of Ordered Water In This Microloopmentioning

confidence: 99%

A hypothesis concerning callose

Gensler¹

2018

Plant Signaling & Behavior

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Background Concept: Certain proteins and the glucose monomer have spacing of their carbonyl oxygen atoms that match the spacing of the oxygen atoms of hexagonal ice. This opens the possibility that a sequence of linked glucose residues may have a sequence of equally spaced carbonyl oxygen atoms. Hypothesis: Callose In plants is a duality consisting of the callose itself and a layer of ordered water whose oxygen atoms are hydrogen bonded to the carbonyl oxygen atoms in the callose. The atomic basis of the hypothesis is that the 1-3 linkage between glucose residues in callose results in equally spaced carbonyl oxygen atoms within and between residues. Properties of Callose/Ordered Water: The physical properties of the duality are the properties of callose itself: 1) it is immobile, 2) it can be created and dissolved, 3) it can exist at a submicrometer to micrometers space scale. The electrical properties of ordered water in a botanical platform are not known at the present time. They can be derived only from limited data in non biological platforms and inferences from the electrical properties of ice. These properties are 1) proton movement is governed by the Grotthuss mechanism, 2) there is insignificant movement of non-protonic ions and larger molecules through the ordered water, 3) proton movement is isotropic. Proposed Functionality of Callose/Ordered Water: Known locations of callose were examined theoretically to determine the functionality of a callose/ordered water duality. These locations were sieve plate pores, plasmodesmata and pollen tubes, stomatal guard cells, companion cell/sieve tube complex and micro and megasporocytes. Protonic Circuits: In a botanical context, protonic circuits at a single cell and supracellular level take the form of a proton microloop wherein callose/ordered water is one component in the loop. These circuits use both the enhanced proton mobility and the ion blocking ability of ordered water. ARTICLE HISTORY

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Diffusion or bulk flow: how plasmodesmata facilitate pre-phloem transport of assimilates

Schulz

2014

J Plant Res

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Assimilates synthesized in the mesophyll of mature leaves move along the pre-phloem transport pathway to the bundle sheath of the minor veins from which they are loaded into the phloem. The present review discusses the most probable driving force(s) for the pre-phloem pathway, diffusion down the concentration gradient or bulk flow along a pressure gradient. The driving force seems to depend on the mode of phloem loading. In a majority of plant species phloem loading is a thermodynamically active process, involving the activity of membrane transporters in the sieve-element companion cell complex. Since assimilate movement includes an apoplasmic step, this mode is called apoplasmic loading. Well established is also the polymer-trap loading mode, where the phloem-transport sugars are raffinose-family oligomers in herbaceous plants. Also this mode depends on the investment of energy, here for sugar oligomerization, and leads to a high sugar accumulation in the phloem, even though the phloem is not symplasmically isolated, but well coupled by plasmodesmata (PD). Hence the mode polymer-trap mode is also designated active symplasmic loading. For woody angiosperms and gymnosperms an alternate loading mode is currently matter of discussion, called passive symplasmic loading. Based on the limited material available, this review compares the different loading modes and suggests that diffusion is the driving force in apoplasmic loaders, while bulk flow plays an increasing role in plants having a continuous symplasmic pathway from mesophyll to sieve elements. Crucial for the driving force is the question where water enters the pre-phloem pathway. Surprisingly, the role of PD in water movement has not been addressed so far appropriately. Modeling of assimilate and water fluxes indicates that in symplasmic loaders a considerable part of water flux happens through the PD between bundle sheath and phloem.

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Plasmodesmata and Phloem: Conduits for Local and Long‐distance Signaling

Cited by 5 publications

References 81 publications

A combinatory approach for analysis of protein sets in barley sieve-tube samples using EDTA-facilitated exudation and aphid stylectomy

A combinatory approach for analysis of protein sets in barley sieve-tube samples using EDTA-facilitated exudation and aphid stylectomy

A hypothesis concerning callose

Diffusion or bulk flow: how plasmodesmata facilitate pre-phloem transport of assimilates

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