Auxin Concentration/Growth Relationship for <i>Avena</i> Coleoptile Sections from Seedlings Grown in Complete Darkness

Shinkle, James R.; Briggs, Winslow R.

doi:10.1104/pp.74.2.335

Cited by 22 publications

(14 citation statements)

References 22 publications

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“…The results were obtained both for sections handled in complete darkness and for sections prepared in complete darkness and then given a red-light pulse at time 0 of the incubation. The IAA doseresponse curve for dark-incubated sections prepared from similar tissue has been described in detail elsewhere (7). The results shown here are consistent with the earlier findings.…”

Section: Methodssupporting

confidence: 92%

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Indole-3-acetic acid sensitization of phytochrome-controlled growth of coleoptile sections

Shinkle¹,

Briggs²

1984

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

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Addition of 6 ,iM indole-3-acetic acid (IAA) to incubation buffer increases the sensitivity of coleoptile sections cut from dark-grown Avena sativa L. cv. Lodi to red light by a factor of 10,000, relative to the response in the absence of added IAA, without changing the maximum amount of lightinduced growth. From 0.03 to 4 IuM IAA sections show at least a 100-fold increase in sensitivity to red light relative to the response in the absence of added IAA. In this IAA concentration range, the light-induced increase in elongation shows two phases of response to red-light fluence, which are separated by a plateau. The biphasic fluence-response curve is also characteristic of the red-light-induced stimulation of coleoptile growth in intact dark-grown seedlings. The effect of IAA on the sensitivity of the phytochrome-mediated growth response appears to be on some step in the transduction of the phytochrome signal, rather than on the growth response itself.Brief irradiation with red light stimulates coleoptile elongation and inhibits mesocotyl elongation in etiolated oat (Avena sativa) seedlings (1, 2). Phytochrome control of such photomorphogenetic growth responses in etiolated cereal seedlings has been studied extensively in whole plants (see ref. 1 for review). Consistent and reproducible results for red-light-induced growth responses have been obtained by performing experiments on intact etiolated oat seedlings grown and handled in complete darkness without the use of green "safelights" (1, 2).Auxins have long been thought to mediate the red-lightinduced changes in growth in etiolated cereal seedlings (3)(4)(5). Cut sections of etiolated tissue have been used to study the phytochrome/auxin interaction, but findings have been inconclusive. In one such study (3), it was reported that indole-3-acetic acid (IAA), a naturally occurring auxin, must be present in the incubation buffer for red-light-stimulated growth and reversal by far-red light to be seen. This finding has not been replicated in subsequent studies (4, 6).There have also been difficulties in comparing the response of sections to the responses to red light seen in intact plants. Studies of the fluence dependence of the red-lightinduced increase in growth in coleoptile sections cut from etiolated seedlings (4, 6) do not report the biphasic fluenceresponse curve characteristic of the whole tissue responses (1, 2). In one of these studies (6), only the less sensitive phase of the red-light response found in whole plants was reported. In another study (4), only the more sensitive phase of the red-light response was detected. The complete lack of the less sensitive response generally seen (1, 2, 6) is unique to this study (4). Neither of the studies of section growth responses to red light (4, 6) included comparable experiments with intact plants.To investigate some of the possibilities suggested by earlier studies, we have adapted the techniques of Mandoli and Briggs (1) for the study of oat coleoptile sections cut in the dark from seedlings grown in co...

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Section: Methodssupporting

confidence: 92%

“…After 12 hr of irradiation, sections were removed and the red-light-induced increase in growth was determined. Harvesting, incubation, and measurement of growth were carried out as described (7). (9,10), shows a threshold of Amol/m2 and becomes saturated at 10-2 AMmol/m2.…”

Section: Methodsmentioning

confidence: 99%

Indole-3-acetic acid sensitization of phytochrome-controlled growth of coleoptile sections

Shinkle¹,

Briggs²

1984

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

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“…8A) have not been reported previously, but biphasic dose response curves have been described. Working with segments of darkgrown oat coleoptiles, Shinkle and Briggs (1984) found a small shoulder on the ascending part of the dose response curve for IAA-induced growth. This shoulder was not evident with NAA.…”

Section: Relationship With Auxin-induced Internode Growthmentioning

confidence: 97%

“…However, the dose response curves for growth have indicated that segments of coleoptiles or stems are at least 10 times more sensitive to IAA (e.g. Shinkle and Briggs, 1984; see also Fig. 8).…”

Section: Relationship With Auxin-induced Internode Growthmentioning

confidence: 99%

Two Distinct Signaling Pathways Participate in Auxin-Induced Swelling of Pea Epidermal Protoplasts

Yamagami

Haga²,

Napier³

et al. 2004

Plant Physiology

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Protoplast swelling was used to investigate auxin signaling in the growth-limiting stem epidermis. The protoplasts of epidermal cells were isolated from elongating internodes of pea (Pisum sativum). These protoplasts swelled in response to auxin, providing the clearest evidence that the epidermis can directly perceive auxin. The swelling response to the natural auxin IAA showed a biphasic dose response curve but that to the synthetic auxin 1-naphthalene acetic acid (NAA) showed a simple bell-shaped dose response curve. The responses to IAA and NAA were further analyzed using antibodies raised against ABP1 (auxin-binding protein 1), and their dependency on extracellular ions was investigated. Two signaling pathways were resolved for IAA, an ABP1-dependent pathway and an ABP1-independent pathway that is much more sensitive to IAA than the former. The response by the ABP1 pathway was eliminated by anti-ABP1 antibodies, had a higher sensitivity to NAA, and did not depend on extracellular Ca 2ϩ . In contrast, the response by the non-ABP1 pathway was not affected by anti-ABP1 antibodies, had no sensitivity to NAA, and depended on extracellular Ca 2ϩ . The swelling by either pathway required extracellular K ϩ and Cl Ϫ . The auxin-induced growth of pea internode segments showed similar response patterns, including the occurrence of two peaks in the dose response curve for IAA and the difference in Ca 2ϩ requirements. It is suggested that two signaling pathways participate in auxin-induced internode growth and that the non-ABP1 pathway is more likely to be involved in the control of growth by constitutive concentrations of endogenous auxin.

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“…All manipulations of plant material, other than explicitly described experimental irradiations and final length measurements, were conducted in complete darkness, as were all incubations ofexperimental matenral. Subapical sections from coleoptiles of Avena sativa L. cv Lodi were obtained from 72 h old dark-grown seedlings, as described previously (22). Sections 5.7 mm long were cut and floated on 5% sucrose solution buffered to a given pH.…”

Section: Methodsmentioning

confidence: 99%

Physiological Mechanism of the Auxin-Induced Increase in Light Sensitivity of Phytochrome-Mediated Growth Responses in Avena Coleoptile Sections

Shinkle¹,

Briggs²

1985

Plant Physiol.

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The physiology of the auxin-induced 10,000-fold increase in light sensitivity of a phytochrome-mediated growth response (Shinkle and Briggs, 1984 Proc Nati Acad Sci USA 81: 3742-3746) has been characterized in subapical coleoptile sections from dark-grown oat (Avena satita L. cv Lodi) seedlings. Six micromolar indole-3-acetic acid (IAA) must be present for 1 hour before to 2 hour after irradiation in order to confer maximal sensitivity to light. The direct effect of IAA on growth can be separated from its effect on light sensitivity. Several classes of synthetic auxins will substitute for IAA in inducing an increase in sensitivity to light, as will both the phytotoxin fusicoccin and treatment of sections with pH 4.5 buffer. The increase in sensitivity to light induced by 6 micromolar IAA is completely inhibited by buffering the sections at pH 5.9 with 30 millimolar 24N-morpholino)ethanesulfonic acid. These findings suggest that the capacity to respond to very low fluences of light is regulated by extracellular pH.Between 10 and 15 millimolar K will inhibit the induction of the increased sensitivity to light, independent of the mechanism of induction. The effect of K appears to be specific to the process-by which the sections respond to very low levels of light.

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Auxin Concentration/Growth Relationship for Avena Coleoptile Sections from Seedlings Grown in Complete Darkness

Cited by 22 publications

References 22 publications

Indole-3-acetic acid sensitization of phytochrome-controlled growth of coleoptile sections

Indole-3-acetic acid sensitization of phytochrome-controlled growth of coleoptile sections

Two Distinct Signaling Pathways Participate in Auxin-Induced Swelling of Pea Epidermal Protoplasts

Physiological Mechanism of the Auxin-Induced Increase in Light Sensitivity of Phytochrome-Mediated Growth Responses in Avena Coleoptile Sections

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