Stimulation of Root Elongation and Curvature by Calcium

Takahashi, Hideyuki; Scott, Tom K.; Suge, Hiroshi

doi:10.1104/pp.98.1.246

Cited by 29 publications

(24 citation statements)

References 21 publications

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“…Takahashi et al (24) reported effects of Ca opposite to ours. They found that application of Ca to the cap stimulated elongation and that unilateral application induced negative curvature by accelerating elongation on the side to which Ca was applied.…”

Section: Plant Materialscontrasting

confidence: 81%

Induction of Curvature in Maize Roots by Calcium or by Thigmostimulation

Ishikawa

Evans²

1992

Plant Physiol.

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We examined the response of primary roots of maize (Zea mays L. cv Merit) to unilateral application of calcium with particular attention to the site of application, the dependence on growth rate, and possible contributions of thigmotropic stimulation during application. Unilateral application of agar to the root cap induced negative curvature whether or not the agar contained calcium. This apparent thigmotropic response was enhanced by including calcium in the agar. Curvature away from objects applied unilaterally to the extreme root tip occurred both in intact and detipped roots. When agar containing calcium chloride was applied to one side of the postmitotic isodiametric growth zone (a region between the apical meristem and the elongation zone), the root curved toward the side of application. This response could not be induced by plain agar. We conclude that curvature away from calcium applied to the root tip results from a thigmotropic response to stimulation during application. In contrast, curvature toward calcium applied to the postmitotic isodiametric growth zone results from direct calcium-induced inhibition of growth. application, (c) localized changes in growth rate accompanying the curvature, and (d) the possible induction of curvature by mechanical stimulation during Ca application. MATERIALS AND METHODS Plant MaterialCaryopses of maize (Zea mays L. cv Merit; Asgrow Seeds, Vineland, NJ) were soaked in tap water overnight and planted between wet paper towels on an opaque plastic tray. A second tray was applied on top and the two trays, forming a sandwich holding the caryopses, were taped together. The trays were held vertically in a pan with the paper towels along the lower end of the tray contacting standing water in the pan. The trays were kept under fluorescent lights (Sylvania coolwhite, approximately 5 jimol m-2 s1'). Seedlings were used when the primary roots were 2 to 3 cm long (about 3 d after soaking).In earlier work, we reported that asymmetric application of Ca near the tips of primary roots of maize causes curvature toward the Ca (17). We also found that immersion of roots in Ca-containing solution causes transient inhibition of elongation (8). Based on these observations, we suggested that curvature toward Ca results from inhibition of root growth by Ca (10).Takahashi et al. (24) reported effects of Ca opposite to ours. They found that application of Ca to the cap stimulated elongation and that unilateral application induced negative curvature by accelerating elongation on the side to which Ca was applied. We also observed curvature away from Ca in some of our experiments (11).Ca has been implicated as a mediator of root gravitropism (2, .17) and may also play a role in the modification of gravitropic behavior by light (18,21,24). In view of the apparent importance of Ca in root gravitropism, we reexamined the phenomenon of Ca-induced curvature with special attention to (a) kinetics, (b) dependence on the site of l Supported by National Aeronautics and Space Administration grant N...

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Section: Plant Materialscontrasting

confidence: 81%

Induction of Curvature in Maize Roots by Calcium or by Thigmostimulation

Ishikawa

Evans²

1992

Plant Physiol.

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“…The requirement for calcium in the ethylene-based triple response proved to be complex because normal hypocotyl elongation required the presence of calcium. Calcium has been shown to be stimulatory to root elongation in pea and corn as well (Takahashi et al, 1992). Interestingly, analysis of Arabidopsis mutants insensitive to ethylene (ein) or that lack the ability to form hooks (his) suggests that hypocotyl hook formation and elongation of hypocotyl and root are independent ethylene responses.…”

Section: Discussionmentioning

confidence: 99%

Calcium Requirement for Ethylene-Dependent Responses.

1992

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Ethylene, a gaseous plant hormone, plays a role in plant development, defense, and climactericfruit ripening. Both genetic and biochemical evidence suggest that the response of plants to ethylene is mediated by a specific ethylene receptor. The signal emanating from the receptor-effector complex is then presumably transduced via an unknown cascade pathway. We have used the plant pathogenesis response, exemplified by the induction of the pathogenesis-related gene chitinase, as a paradigm to investigate ethylene-dependent signal transduction in the plant cell. We showed that calcium is necessarily involved in the ethylene-mediated pathogenesis response. Blocking calcium fluxes with chelators inhibited ethylene-dependent induction of chitinase accumulation, but not ethylene independent induction. Artificially increasing cytosolic calcium levels by treatments with the calcium ionophore ionomycin or the calcium pump blocker thapsigargin stimulated chitinase accumulation. Plants grown in calcium-poor soil showed a 10-fold reduction in leaf extractable calcium. Their leaves exhibited a reduced pathogenesis reaction to ethylene and were impaired in another hormone response mediated by calcium, i.e., abscisic acid-controlled closure of guard cells. The addition of calcium to leaves excised from calcium-deficient plants rsstored their sensitivity to ethylene. Ethylene participates in the control of seedling growth, promoting the so-called "triple response" that results in distinct morphological development, such as hypocotyl hook formation. This effect, similar to the ethylene-promoted pathogenesis response, was found to be calcium dependent. The results indicate that calcium is required for a variety of ethylene-dependent processes.

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“…However, the evidence has been indirect and sometimes contradictory. For example, unilateral application of Ca 2+ via agar blocks, which has often been cited as evidence for a role of Ca 2 + asymmetries in the root graviresponse, do not always lead to the same result (Hasenstein et al, 1988;Ishikawa and Evans, 1992;Takahashi et al, 1992). Ca 2< transport studies have shown the preferential polar transport of 45 Ca 2 ' toward the lower side of graviresponding maize roots (Lee et al, 1983b), but no asymmetry in free Ca 2+ between upper and lower sides of the roots could be detected (Dauwalder et al, 1985).…”

Section: Discussionmentioning

confidence: 99%

Cytoplasmic Free Ca2+ in Arabidopsis Roots Changes in Response to Touch but Not Gravity

et al. 1997

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Changes in cytoplasmic Ca2+ concentration ([Ca2+];) have been proposed to be involved in signal transduction pathways in response to a number of stimuli, including gravity and touch. The current hypothesis proposes that the development of gravitropic bending is correlated with a redistribution of [Caz+li in gravistimulated roots.However, no study has demonstrated clearly the development of an asymmetry of this ion during root curvature. We tested this hypothesis by quantifying the temporal and spatial changes i n [Ca2+]; in roots of living Arabidopsis seedlings using ultraviolet-confocal Ca2+-ratio imaging and vertical stage fluorescence microscopy to visualize root [Ca2+li. We observed no changes i n [Ca*+], associated with the graviresponse whether monitored at the whole organ leve1 or i n individual cells in different regions of the root for up to 12 h after gravistimulation. However, touch stimulation led to transient increases in [Ca"]; in all cell types monitored. The increases induced in the cap cells were larger and longer-lived than i n cells i n the meristematic or elongation zone. One millimolar La3+ and 1 O0 WM verapamil did not prevent these responses, whereas 5 mM ECTA or 50 WM ruthenium red inhibited the transients, indicating an intracellular origin of the CaZ+ increase. These results suggest that, although touch responses of roots may be mediated through a Ca2+-dependent pathway, the gravitropic response is not associated with detectable changes i n [Ca2+],.When positioned horizontally a root responds by curving downward toward the gravity vector. The positive gravitropic response of roots depends on a series of events: gravity perception, translocation of the gravity stimulus to the site of the response, and the tropic-growth response. The latter is characterized by asymmetric growth across the elongation zone, with reduced growth along the lower side compared with the upper side (Ishikawa et al., 1991). The gravity-sensing cells in the root are thought to be the cells of the starch-containing columella in the cap. A widely used model for root gravitropism is that sedimentation of amyloplasts in the columella (Sack, 1991) leads to asym-

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Stimulation of Root Elongation and Curvature by Calcium

Cited by 29 publications

References 21 publications

Induction of Curvature in Maize Roots by Calcium or by Thigmostimulation

Induction of Curvature in Maize Roots by Calcium or by Thigmostimulation

Calcium Requirement for Ethylene-Dependent Responses.

Cytoplasmic Free Ca2+ in Arabidopsis Roots Changes in Response to Touch but Not Gravity

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