Reversible Calcium-Regulated Stopcocks in Legume Sieve Tubes [W]

Abstract

Sieve tubes of legumes (Fabaceae) contain characteristic P-protein crystalloids with controversial function. We studied their behavior by conventional light, electron, and confocal laser scanning microscopy. In situ, crystalloids are able to undergo rapid ( Ͻ 1 sec) and reversible conversions from the condensed resting state into a dispersed state, in which they occlude the sieve tubes. Crystalloid dispersal is triggered by plasma membrane leakage induced by mechanical injury or permeabilizing substances. Similarly, abrupt turgor changes imposed by osmotic shock cause crystalloid dispersal. Because chelators generally prevent the response, divalent cations appear to be the decisive factor in crystalloid expansion. Cycling between dispersal and condensation can be induced in opened cells by repetitive exchange of bathing media containing either Ca 2 ؉ or chelators. Sr 2 ؉ and Ba 2 ؉ , but not Mg 2 ؉ , are equally active. In conclusion, the fabacean P-protein crystalloids represent a novel class of mechanically active proteinaceous structures, which provide an efficient mechanism with which to control sieve tube conductivity.

Sap flow and sugar transport in plants

“…Several have investigated phloem translocation speeds by further developing this dye tracing approach (Schumacher, 1948;Froelich et al, 2011;Jensen et al, 2011;Savage, Zwieniecki, and Holbrook, 2013). Dyes have also been used to quantify the capacity of loading and unloading pathways (Oparka et al, 1994;Liesche and Schulz, 2012), as well as the impact of wounding on a sieve element function (Schulz, 1992;Knoblauch et al, 2001).…”

Sensing Technologies for Precision Phenotyping in Vegetable Crops: Current Status and Future Challenges

“…MR imaging (MRI) systems rely on the quantitative measure of the presence and the movement of water in plants, for which organs compete, in particular during fruit development. One of the major constraints for the measurement of sap-flow (the fluid transported in xylem cells), is the extreme sensitivity to invasive experimentation [121]. MRI and NMR are able to overcome this gap, since they record the displacement of water inside the plant through imaging analysis.…”

Calcium powered phloem protein ofSEOgene family “Forisome” functions in wound sealing and act as biomimetic smart materials

“…The increase in free Ca 2+ caused due to mechanical damage occurs in all irrespective of the plant species and family. 26,27 Despite the wealth of experimental data, very little is known about P-proteins at the molecular level. The first structural P-protein to be characterized was phloem protein 1 (PP1) from squash (Cucurbita maxima).…”

“…46,47 On the basis of dynamic structural changes which are unique to the crystalline P-proteins of legumes distinguishes them from the non-dispersive phloem-specific protein bodies of other families (such as Urticaceae and Rosaceae). 48 Classically the phloem protein bodies have been classified namely into 2 broad categories. 9 They are referred to as "nondispersive" and "dispersive" protein bodies.…”