Auxin Gradient Theory of Abscission Regulation

Addicott, Fredrick T.; Lynch, Ruth Stocking; Carns, H. R.

doi:10.1126/science.121.3148.644

Cited by 77 publications

(32 citation statements)

References 12 publications

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“…Application of IAA to the distal end of abscission zone explants delayed abscission, while addition to the proximal end promoted abscission (Addicott and Lynch, 1951). This suggests that changes in auxin gradients may signal the onset of or enhance senescence and may explain the observation that treating whole plants with auxin had little effect on abscission (Addicott et al, 1955). These conclusions also raise the possibility that ARF1, ARF2, NPH4/ARF7 and ARF19 may interact in some way to read auxin gradients.…”

Section: Auxin and Senescencementioning

confidence: 50%

AUXIN RESPONSE FACTOR1andAUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission inArabidopsis thaliana

et al. 2005

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In plants, both endogenous mechanisms and environmental signals regulate developmental transitions such as seed germination, induction of flowering,leaf senescence and shedding of senescent organs. Auxin response factors(ARFs) are transcription factors that mediate responses to the plant hormone auxin. We have examined Arabidopsis lines carrying T-DNA insertions in AUXIN RESPONSE FACTOR1 (ARF1) and ARF2 genes. We found that ARF2 promotes transitions between multiple stages of Arabidopsis development. arf2 mutant plants exhibited delays in several processes related to plant aging, including initiation of flowering, rosette leaf senescence, floral organ abscission and silique ripening. ARF2 expression was induced in senescing leaves. ARF2 regulated leaf senescence and floral organ abscission independently of the ethylene and cytokinin response pathways. arf1 mutations enhanced many arf2 phenotypes, indicating that ARF1 acts in a partially redundant manner with ARF2. However, unlike arf2mutations, an arf1 mutation increased transcription of Aux/IAA genes in Arabidopsis flowers, supporting previous biochemical studies that indicated that ARF1 is a transcriptional repressor. Two other ARF genes, NPH4/ARF7 and ARF19, were also induced by senescence,and mutations in these genes enhanced arf2 phenotypes. NPH4/ARF7 and ARF19 function as transcriptional activators, suggesting that auxin may control senescence in part by activating gene expression.

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Section: Auxin and Senescencementioning

confidence: 50%

AUXIN RESPONSE FACTOR1andAUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission inArabidopsis thaliana

et al. 2005

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“…Experiments with bean leaves suggested that changes in auxin gradients rather than the auxin concentration itself may modulate abscission and senescence development (Addicott et al, 1955). Of 13 TPs (suspected to be) involved in auxin transport, six are massively down-regulated in NS, DIS, and DET (Supplemental Fig.…”

Section: Auxinmentioning

confidence: 99%

Transcription Analysis of Arabidopsis Membrane Transporters and Hormone Pathways during Developmental and Induced Leaf Senescence

et al. 2006

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A comparative transcriptome analysis for successive stages of Arabidopsis (Arabidopsis thaliana) developmental leaf senescence (NS), darkening-induced senescence of individual leaves attached to the plant (DIS), and senescence in dark-incubated detached leaves (DET) revealed many novel senescence-associated genes with distinct expression profiles. The three senescence processes share a high number of regulated genes, although the overall number of regulated genes during DIS and DET is about 2 times lower than during NS. Consequently, the number of NS-specific genes is much higher than the number of DIS-or DET-specific genes. The expression profiles of transporters (TPs), receptor-like kinases, autophagy genes, and hormone pathways were analyzed in detail. The Arabidopsis TPs and other integral membrane proteins were systematically reclassified based on the Transporter Classification system. Coordinate activation or inactivation of several genes is observed in some TP families in all three or only in individual senescence types, indicating differences in the genetic programs for remobilization of catabolites. Characteristic senescence type-specific differences were also apparent in the expression profiles of (putative) signaling kinases. For eight hormones, the expression of biosynthesis, metabolism, signaling, and (partially) response genes was investigated. In most pathways, novel senescence-associated genes were identified. The expression profiles of hormone homeostasis and signaling genes reveal additional players in the senescence regulatory network.

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“…Results obtained from the influence of auxin on the abscission of explants have supplied the basis of the "auxin gradient theory" as proposed by Addicott et al (2,3). The theory holds that if the auxin concentration is higher on the proximal side of the abseission zone, abscission is accelerated.…”

mentioning

confidence: 99%

Factors Influencing Abscission.

Biggs¹,

Leopold²

1957

Plant Physiol.

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The hormonal concept of abscission control was spearheaded by the suggestive experiments of Laibach in 1933 (15) and then more specifically established by the experiments of La Rue (17) in which he found that indoleacetic acid, pollen extracts, or urine could delay the abscission of debladed petioles. Since that time, numerous reports have added substantial support to the idea that auxins control abscission through an inhibitory influence (1,10,19, 25). More recently the concept of hormonal control has been extended to include auxin promotion of abscission as well (1,11).A useful tool for studying the effects of various substances on abscission has been the petiole explant test described by Addicott et al (4). This test with modification has been used subsequently by a number of workers: by Livingston (18) to study the effects of ethylene, sucrose, and auxins on abscission; by Carns (6) to study the influence of metabolic inhibitors; by Osborne (21) to seek a natural factor which promotes abscission; and by Gaur and Leopold (11) to study the quantitative effects of auxin on abscission.It has been observed in this laboratory that explant tests performed under similar conditions but at different times showed a considerable degree of variation and in fact in some tests no abscission occurred at all. The following experiments were undertaken to establish a more reliable explant test and to clarify some of the factors influencing abscission. Interactions between leaf age, substrates, light and auxin are described.MATERIAL AND METHODS Seedlings of Phaseolus vulgaris L. var. Red Kidney, were grown in flats in the greenhouse on a 16-hour-day. Daylength was extended with incandescent lamps giving approximately 70 ft-c at plant level.Explants 1 cm in length were taken from the primary leaves to include 5 mm of petiole and 5 mm of pulvinus tissue. These explants were placed in 5-cm Petri dishes, basal end down, to a 4-mm depth in 1 % agar with or without addenda. There were 20 explants per treatment. Each experiment reported here was repeated in its entirety at least 3 times and the results are consistent with 35 other experiments encompassing variations on these reported ones. Napthaleneacetic acid (NAA) was incorporated into the agar as its ammonium salt. No organic solvent was used to dissolve the auxin.Light treatments given to the explants involved a 12-hr day w ith 300 ft-c light intensity supplied by

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Auxin Gradient Theory of Abscission Regulation

Cited by 77 publications

References 12 publications

AUXIN RESPONSE FACTOR1andAUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission inArabidopsis thaliana

AUXIN RESPONSE FACTOR1andAUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission inArabidopsis thaliana

Transcription Analysis of Arabidopsis Membrane Transporters and Hormone Pathways during Developmental and Induced Leaf Senescence

Factors Influencing Abscission.

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