Light‐ and Clock‐Controlled Leaflet Movements in <i>Samanea saman</i>*: A Physiological, Biophysical and Biochemical Analysis**

Satter, Ruth L.; Morse, M. J.; Lee, Youngsook; Crain, Richard C.; Coté, Gary G.; Moran, Nava

doi:10.1111/j.1438-8677.1988.tb00034.x

Cited by 64 publications

(47 citation statements)

References 85 publications

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“…It has been proposed that hyperpolarization-gated K+ channels permit inward-directed K+ fluxes in both extensor and flexor cells (9,17). Our data, however, indicate that membrane hyperpolarization caused by activation of the H+-ATPase is not the sole factor controlling inward K+ fluxes.…”

Section: Signal Transductioncontrasting

confidence: 72%

Effects of Light on the Membrane Potential of Protoplasts from Samanea saman Pulvini

Kim

Coté²,

Crain³

1992

Plant Physiol.

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Rhythmic light-sensitive movements of the leaflets of Samanea saman depend upon ion fluxes across the plasma membrane of extensor and flexor cells in opposing regions of the leaf-movement organ (pulvinus). We have isolated protoplasts from the extensor and flexor regions of S. saman pulvini and have examined the effects of brief 30-second exposures to white, blue, or red light on the relative membrane potential using the fluorescent dye, 3,3'-dipropylthiadicarbocyanine iodide. White followed by darkness (7,8). Similarly, during circadianrhythmic leaflet movement, K+, Cl-, and water are taken up alternately and rhythmically by flexor and extensor cells (2).The plasma membrane H+-ATPase of plant cells has a primary role in coupling ATP hydrolysis to solute movement (22). Outwardly directed H+ transport by the H+-ATPase produces both a membrane electrical potential and a pH gradient. The membrane electrical potential drives the uptake of cations, mainly K+, whereas the pH gradient promotes the uptake of anions such as Cl-and neutral molecules such as sucrose through H+-coupled cotransport. For example, during blue light-induced opening of leaf stomata, H+ extrusion from guard cells creates an electrical gradient that drives K+ uptake through K+-selective ion channels (1,18,19); stomatal opening is inhibited by the H+-ATPase inhibitor vanadate (21). Irradiation of isolated S. saman pulvini also causes H+ fluxes, membrane potential changes, and K+ movement, which regulate pulvinar bending and, hence, mediate light-induced leaflet movement (7,8). Similarly, opposing changes observed in apoplastic H+ and K+ concentrations in the extensor region of the Phaseolus pulvinus also support a role for the H+-ATPase in K+ uptake during rhythmic leaflet movement (24). Potassium channels have been described in cells involved in turgor-mediated movements. Voltage-gated K+ channels activated by membrane depolarization have been observed in patch-clamp studies of plasma membranes of S. saman protoplasts (9) and of Vicia faba guard cell protoplasts (19,20). These channels might serve as the pathway for K+ efflux from shrinking cells. Hyperpolarization-activated K+ channels have been reported in guard cell protoplasts of V. faba (20) and in S. saman protoplasts (9). These channels might serve as a pathway for K+ influx into swelling cells.We are studying the transduction pathway mediating lightinduced changes in K+ flux. We have examined the effect of light on K+ channels by measuring the relative membrane potential of S. saman protoplasts exposed to light and the sensitivity of this potential to external K+. We present evidence here that white and blue light induce K+ channel opening in the plasma membranes of extensor protoplasts while inducing K+ channel closure in the plasma membranes of flexor protoplasts.

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Section: Signal Transductioncontrasting

confidence: 72%

Effects of Light on the Membrane Potential of Protoplasts from Samanea saman Pulvini

Kim

Coté²,

Crain³

1992

Plant Physiol.

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“…The direct effect of light in opening the leaflets is also due to promotion of the inward movement of these solutes. Satter et al (1988) proposed that ionic movement through the plasmalemma is driven by a proton pump transporting H^ ions out of the cell. This process creates a proton motive force across the plasmalemma which consists of an electrical potential difference and a pH gradient.…”

Section: Organismsmentioning

confidence: 99%

“…The membranes of the motor cells contain depolarization-activated, K^-selective channels which provide the pathways for outward movement of K"^ ions in cells losing their turgor (Moran, Fox & Satter, 1990), and there is evidence that they also possess a hyperpolarization-activated channel for K^ diffusion into the cells increasing their turgidity (Satter et al, 1988). There is co-transport of Cl" into the motor cells.…”

Section: Organismsmentioning

confidence: 99%

Tansley Review No. 37 Circadian rhythms: their origin and control

Wilkins

1992

New Phytologist

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SUMMARY This article reviews the circadian rhythm of carbon dioxide metabolism in leaves of the Crassulacean plant Bryophyllum (Kalanchoë) fedtsckenkoi which persists both in continuous darkness and a CO2‐free atmosphere, and in continuous light and normal air. Under both conditions the rhythm is due to the periodic activity of the enzyme phosphoenolpyruvate carboxylase (PEPc). The physiological characteristics of the rhythm are described in detail and, from these characteristics, hypotheses are advanced to account for both the generation of the rhythm and the regulation of its phase and period by environmental factors. The periodic activity of PEPc is ascribed to the periodic accumulation of an allosteric inhibitor, malate, in the cytoplasm and its subsequent removal either to the vacuole in continuous darkness, or by metabolism in continuous light. Also involved in the generation of the rhythm is a periodic change in the sensitivity of PEPc to malate inhibition due to the periodic phosphorylation and dephosphorylation of PEPc which changes its K1 by a factor of 10 from 30 to 0.3 mM and vice versa. This periodic phosphorylation of PEPc is apparently achieved by the periodic synthesis and breakdown of a PEPc kinase which phosphorylates the enzyme on a serine residue; dephosphorylation is achieved by a type 2A phosphatase which shows no rhythmic variation. The induction of phase shifts in the rhythm in continuous darkness and CO2‐free air has been explained in terms of light and high‐temperature activated gates or channels in the tonoplast which, when open, allow malate to diffuse between the vacuole and cytoplasm. For the rhythm in continuous light and normal air phase, control by environmental signals can be attributed to changes in the malate levels in critical cell compartments, or in particular cell populations such as the stomatal guard cells, due to regulation of the malate synthesizing enzyme system involving PEPc, and malic enzyme which is responsible for malate metabolism. The role of the stomata in the generation of the rhythm is also discussed. The biochemical events which appear to give rise to the well‐studied circadian rhythms in leaf movement in Samanea and Albizza, in luminescence in Gonyaulax polyedra and in the synthesis of the chlorophyll a/b binding protein are also reviewed in an attempt to identify similarities between these events and those involved in the Bryophyllum rhythm. Finally, the somewhat similar nature of the genes apparently responsible for circadian rhythmicity in Neurospora and Drosophila are discussed, and suggestions made for utilizing anti‐sense nucleic acid technology in the further elucidation of the critical biochemical events involved in the basic, temperature‐compensated circadian oscillator in living organisms.

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“…Plant growth, differentiation, cell and tissue polarity, as well as movements strongly depend on the formation of pH gradients across individual cell types (1)(2)(3). Stomata that are formed by two guard cells represent a unique model for plant movement.…”

mentioning

confidence: 99%

Molecular basis of plant-specific acid activation of K ⁺ uptake channels

Hoth¹,

Drèyer²,

Dietrich³

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

123

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During stomatal opening potassium uptake into guard cells and K ؉ channel activation is tightly coupled to proton extrusion. The pH sensor of the K ؉ uptake channel in these motor cells has, however, not yet been identified. Electrophysiological investigations on the voltage-gated, inward rectifying K ؉ channel in guard cell protoplasts from Solanum tuberosum (KST1), and the kst1 gene product expressed in Xenopus oocytes revealed that pH dependence is an intrinsic property of the channel protein. Whereas extracellular acidification resulted in a shift of the voltage-dependence toward less negative voltages, the single-channel conductance was pH-insensitive. Mutational analysis allowed us to relate this acid activation to both extracellular histidines in KST1. One histidine is located within the linker between the transmembrane helices S3 and S4 (H160), and the other within the putative pore-forming region P between S5 and S6 (H271). When both histidines were substituted by alanines the double mutant completely lost its pH sensitivity. Among the single mutants, replacement of the pore histidine, which is highly conserved in plant K ؉ channels, increased or even inverted the pH sensitivity of KST1. From our molecular and biophysical analyses we conclude that both extracellular sites are part of the pH sensor in plant K ؉ uptake channels.Plant growth, differentiation, cell and tissue polarity, as well as movements strongly depend on the formation of pH gradients across individual cell types (1-3). Stomata that are formed by two guard cells represent a unique model for plant movement. Regulation of stomatal movement in higher plants is essential for efficient uptake of CO 2 at minimal water loss. Stomatal opening requires accumulation of potassium ions into guard cells. K ϩ uptake is mediated by K ϩ uptake channels, a process accompanied by the acidification of the apoplast (4-7). Due to differential pumping activity of the plasma membrane H ϩ -pump the apoplastic pH around closed and open stomata varies between 7 and 5 (8, 9). Within this range changes in the extracellular proton concentration affect the activity of guard cell inward rectifying K ϩ channels (10-13). In contrast to their functional and structural animal counterparts, which are either not activated or even inhibited by protons (14, 15), the guard cell K ϩ channel is activated upon extracellular acidification (10-13).The molecular cloning of plant K ϩ inward rectifiers revealed a structural homology to animal outward rectifying K ϩ channels of the Shaker gene family (12,16,17). Hydrophobicity analyses of their primary structure predicted six transmembrane domains (S1-S6) (12,16,17). Whereas S4 is likely to represent the voltage sensor of these voltage-dependent channels, the amphiphilic linker between S5 and S6 (P) forms the conductive pore (18). Based on the current molecular model of the Shaker channel we were able to relate structural elements of guard cell K ϩ inward rectifiers to stomatal physiology. In this context we have previously sho...

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Light‐ and Clock‐Controlled Leaflet Movements in *Samanea saman: A Physiological, Biophysical and Biochemical Analysis

Cited by 64 publications

References 85 publications

Effects of Light on the Membrane Potential of Protoplasts from Samanea saman Pulvini

Effects of Light on the Membrane Potential of Protoplasts from Samanea saman Pulvini

Tansley Review No. 37 Circadian rhythms: their origin and control

Molecular basis of plant-specific acid activation of K ⁺ uptake channels

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Light‐ and Clock‐Controlled Leaflet Movements in Samanea saman*: A Physiological, Biophysical and Biochemical Analysis**

Cited by 64 publications

References 85 publications

Effects of Light on the Membrane Potential of Protoplasts from Samanea saman Pulvini

Effects of Light on the Membrane Potential of Protoplasts from Samanea saman Pulvini

Tansley Review No. 37 Circadian rhythms: their origin and control

Molecular basis of plant-specific acid activation of K + uptake channels

Contact Info

Product

Resources

About

Light‐ and Clock‐Controlled Leaflet Movements in *Samanea saman: A Physiological, Biophysical and Biochemical Analysis

Molecular basis of plant-specific acid activation of K ⁺ uptake channels