The plant hormone auxin: Insight in sight

Estelle, Mark

doi:10.1002/bies.950140703

Cited by 55 publications

(40 citation statements)

References 50 publications

(15 reference statements)

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“…Exaggerated epinasty and shorter internode length are phenotypes consistent with the negative regulation of ethylene responses by LeETR1. Nevertheless, these are complex phenotypes that are responsive to multiple stimuli (Ursin and Bradford, 1989;Estelle, 1992;Lehman et al, 1996). However, based on a negative regulation model, delayed abscission is perhaps the opposite of what might be expected in plants with reduced ethylene receptor because ethylene typically accelerates abscission (Sexton and Roberts, 1982).…”

Section: Discussionmentioning

confidence: 99%

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Delayed Abscission and Shorter Internodes Correlate with a Reduction in the Ethylene Receptor LeETR1 Transcript in Transgenic Tomato

et al. 2002

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Stable transformation of tomato (Lycopersicon esculentum cv Ailsa Craig) plants with a construct containing the antisense sequence for the receiver domain and 3Ј-untranslated portion of the tomato ethylene receptor (LeETR1) under the control of an enhanced cauliflower mosaic virus 35S promoter resulted in some expected and unexpected phenotypes. In addition to reduced LeETR1 transcript levels, the two most consistently observed phenotypes in the transgenic lines were delayed abscission and reduced plant size. Fruit coloration and softening were essentially unaffected, and all the seedlings from first generation seed displayed a normal triple response to ethylene. Two independent lines with a single copy of the transgene and reduced LeETR1 transcript accumulation were selected for detailed phenotypic analysis of second generation (R1) plants. Delayed abscission, shorter internode length, and reduced auxin movement all correlated with the presence of the transgene and the degree of reduced LeETR1 transcript accumulation. No significant differences were noted for fruit coloration or fruit softening on R1 plants and all seedlings from R1 and R2 seed displayed a normal triple response. LeETR2 transcript accumulation was only slightly reduced in the R1 plants compared with azygous plants, and LeETR3 (NR) transcript levels appeared to be unaffected by the transgene. We propose that ethylene signal transduction occurs through parallel paths that partially intersect to regulate shared ethylene responses. Chang et al. (1993) described the cloning and characterization of the gene, AtETR1, responsible for a dominant ethylene-insensitive mutant in Arabidopsis and discovered that it shared many similarities with two-component regulators in yeast (Saccharomyces cerevisiae) and bacteria. Expression of the AtETR1 gene in yeast generated ethylene-binding sites with similar affinity for ethylene to that estimated from the dose response curve for ethylene inhibition of hypocotyl growth of Arabidopsis seedlings (Schaller and Bleecker, 1995). The AtETR1 ethylene receptor has three domains: a sensor, a His kinase, and a receiver domain (response regulator). Ethylene is bound within the N-terminal sensor domain that includes three membrane-spanning helices (Schaller and Bleecker, 1995). The predicted His kinase domain of the AtETR1 gene product is autophosphorylated (Gamble et al., 1998). Mutation of the His or other putative catabolic residues in the His domainabolished autophosphorylation of AtETR1 (Gamble et al., 1998). However, a function for the His kinase has not been determined. Moreover, a function for the putative receiver domain is also unknown. Based on similarity with other two component systems, phosphorylation of the conserved Asp group in the receiver domain may serve to propagate a signal received by the sensor domain; however, an essential role for the Asp in ethylene signal transduction has not been established (Chang and Shockey, 1999).There are currently five characterized genes that make up a family of ethylene r...

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Section: Discussionmentioning

confidence: 99%

“…3E). Auxin influences both abscission and cell elongation (Sexton and Roberts, 1982;Estelle, 1992). To determine if auxin movement or metabolism may be altered in the transgenic plants, the basipetal and acropetal movement and accumulation of 3 H-labeled IAA were measured in 3-cm stem sections.…”

Section: Stem Internode Length and Iaa Movement In R1 Plantsmentioning

confidence: 99%

Delayed Abscission and Shorter Internodes Correlate with a Reduction in the Ethylene Receptor LeETR1 Transcript in Transgenic Tomato

et al. 2002

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“…Auxins are involved in many aspects of plant growth and development and have long been known to control diverse responses to external stimuli (Went, 1939;Estelle, 1992;Davies, 1995). More recently, auxin signals have also been implicated in the development of cell patterns, for example, in the early embryo, the vascular tissue and the apical meristems (Sachs, 1991;Sabatini et al, 1999;Reinhardt et al, 2000;Berleth and Chatfield, 2002).…”

Section: Introductionmentioning

confidence: 99%

Overlapping and non-redundant functions of theArabidopsisauxin response factorsMONOPTEROSandNONPHOTOTROPIC HYPOCOTYL 4

et al. 2004

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Transcription factors of the auxin response factor (ARF) family have been implicated in auxin-dependent gene regulation, but little is known about the functions of individual ARFs in plants. Here, interaction assays, expression studies and combinations of multiple loss- and gain-of-function mutants were used to assess the roles of two ARFs, NONPHOTOTROPIC HYPOCOTYL 4 (NPH4/ARF7)and MONOPTEROS (MP/ARF5), in Arabidopsis development. Both MP and NPH4 interact strongly and selectively with themselves and with each other,and are expressed in vastly overlapping domains. We show that the regulatory properties of both genes are far more related than suggested by their single mutant phenotypes. NPH4 and MP are capable of controlling both axis formation in the embryo and auxin-dependent cell expansion. Interaction of MP and NPH4 in Arabidopsis plants is indicated by their joint requirement in a number of auxin responses and by synergistic effects associated with the co-overexpression of both genes. Finally, we demonstrate antagonistic interaction between ARF and Aux/IAAgene functions in Arabidopsis development. Overexpression of MP suppresses numerous defects associated with a gain-of-function mutation in BODENLOS (BDL)/IAA12. Together these results provide evidence for the biological relevance of ARF-ARF and ARF-Aux/IAA interaction in Arabidopsis plants and demonstrate that an individual ARF can act in both invariantly programmed pattern formation as well as in conditional responses to external signals.

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“…Cite this article as Cold Spring Harb Perspect Biol 2010;2:a004572 fundamentals of plant development and physiology in the late 1980s (Meyerowitz and Pruitt 1985;Meyerowitz 1987), genetic approaches have been developed to dissect hormone action in this reference species (Klee and Estelle 1991;Estelle 1992). A forward genetic strategy based on root growth inhibition by auxin was taken in parallel to the pursuit of the early gene concept and validated the importance of the ARF-Aux/IAA circuit for auxin-regulated transcription and directly guided the way into the realm of auxin perception.…”

Section: Odyssey Of Auxinmentioning

confidence: 99%

Odyssey of Auxin

Abel¹,

Theologis²

2010

Cold Spring Harbor Perspectives in Biology

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The history of plant biology is inexorably intertwined with the conception and discovery of auxin, followed by the many decades of research to comprehend its action during growth and development. Growth responses to auxin are complex and require the coordination of auxin production, transport, and perception. In this overview of past auxin research, we limit our discourse to the mechanism of auxin action. We attempt to trace the almost epic voyage from the birth of the hormonal concept in plants to the recent crystallographic studies that resolved the TIR1-auxin receptor complex, the first structural model of a plant hormone receptor. The century-long endeavor is a beautiful illustration of the power of scientific reasoning and human intuition, but it also brings to light the fact that decisive progress is made when new technologies emerge and disciplines unite.T he simple hormone related to tryptophan, indole-3-acetic acid (IAA or auxin), has probably been the most intensely studied molecule in plants as it impacts virtually every facet during their life cycle. In fact, a total failure in IAA production has not been reported for any plant alive. Thus, it is not surprising that auxin biology is one of the oldest fields of experimental plant research and that the underlying mechanisms of its action have captivated many generations of scientists.The regulation of growth and development by IAA is largely executed via the coordination of a triumvirate of complex processes: auxin metabolism, auxin translocation, and auxin response. The intricate maze of metabolic reactions related to IAA, encompassing its spatio-temporal patterns of biosynthesis, reversible conjugation, and degradation, is still unfolding. For example, significant progress has been made charting the biosynthetic pathways by a combination of genetic and biochemical approaches, which revealed the operation of at least five different routes to IAA. Our current understanding of the redundant metabolic processes that determine auxin supply has recently been reviewed (Woodward and Bartel 2005;Delker et al. 2008;Chandler 2009). The delivery of auxin from its biosynthetic sources to its sites of perception follows two major, unrelated modes of transportation: rapid longdistance movement via the phloem sap, and slower cell-to-cell distribution over shorter distances. The latter process is unique among

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The plant hormone auxin: Insight in sight

Cited by 55 publications

References 50 publications

Delayed Abscission and Shorter Internodes Correlate with a Reduction in the Ethylene Receptor LeETR1 Transcript in Transgenic Tomato

Delayed Abscission and Shorter Internodes Correlate with a Reduction in the Ethylene Receptor LeETR1 Transcript in Transgenic Tomato

Overlapping and non-redundant functions of theArabidopsisauxin response factorsMONOPTEROSandNONPHOTOTROPIC HYPOCOTYL 4

Odyssey of Auxin

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