Transport of Indole-3-Acetic Acid during Gravitropism in Intact Maize Coleoptiles

Parker, K.; Briggs, Winslow R.

doi:10.1104/pp.94.4.1763

Cited by 65 publications

(42 citation statements)

References 17 publications

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“…Went (2) and Cholodny (3) could show that this substance, called auxin, is laterally translocated in photostimulated coleoptiles, resulting in a curvature of the plant toward the light source. Using radioactively labeled auxin, Parker and Briggs (4) and Iino (5) confirmed the Cholodny-Went hypothesis (6). Whereas lateral auxin translocation in photostimulated maize seedlings is restricted to the tip (7), auxin redistribution in gravistimulated seedlings occurs along the length of the entire coleoptile (8).…”

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confidence: 85%

Blue light regulates an auxin-induced K ⁺ -channel gene in the maize coleoptile

Fuchs¹,

Philippar²,

Ljung³

et al. 2003

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

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Auxin redistribution along gravistimulated maize coleoptiles causes differential expression of the auxin-induced K ؉ -channel gene ZMK1 (Zea mays K ؉ channel 1) and precedes the curvature response. To evaluate the role of ZMK1 during phototropism, we here investigated blue light-stimulated coleoptiles. Four hours of blue light stimulation resulted in phototropic bending (23°). Rotation on a clinostat, at nominally ''zero'' gravity, and simultaneous stimulation with unidirectional blue light, however, resulted in up to 51°bending toward the light. Differential ZMK1 transcription reached a maximum after 90 min of blue light stimulation under gravity, whereas ZMK1 expression remained asymmetric for at least 180 min in photostimulated coleoptiles on a clinostat. We therefore conclude that the stronger phototropic bending under nominally ''zero'' gravity results from prolonged differential expression of ZMK1. Under both conditions, asymmetric expression of ZMK1 could be superimposed on the lateral auxin gradient across the coleoptile tip, whereas the gene for the blue light receptor phototropin 1 (PHOT1), expressed in the tip only, was not differentially regulated in response to blue light. The activation of the two different receptors eliciting the photo-and gravitropic response of the coleoptile thus feeds into a common signaling pathway, resulting in auxin redistribution in the coleoptile tip and finally in differential transcription of ZMK1. In the process of signal integration, gravity transduction restricts the magnitude of the blue light-inducible ZMK1 gradient. The spatial and temporal distribution of ZMK1 transcripts and thus differential K ؉ uptake in both flanks of the coleoptile seem to limit the stimulus-induced bending of this sensory organ. Studying the tropistic curvature of plant organs, Charles Darwin (1) postulated the existence of a signal molecule being synthesized in the tip of photostimulated grass coleoptiles and enhancing growth in one flank of the organ. Went (2) and Cholodny (3) could show that this substance, called auxin, is laterally translocated in photostimulated coleoptiles, resulting in a curvature of the plant toward the light source. Using radioactively labeled auxin, Parker and Briggs (4) and Iino (5) confirmed the Cholodny-Went hypothesis (6). Whereas lateral auxin translocation in photostimulated maize seedlings is restricted to the tip (7), auxin redistribution in gravistimulated seedlings occurs along the length of the entire coleoptile (8). Tropistic curvature is preceded by the asymmetric distribution of apoplastic protons (9), the drop in extracellular pH being caused by increased indole-3-acetic acid (IAA) levels in the fastergrowing flank of the organ (for the Acid Growth Theory, see ref. Although the incoming signal is transduced with the help of one single phytohormone, signal perception is different in graviand photostimulated plants. The light signal is perceived by photoreceptor proteins (phototropins). In Arabidopsis thaliana, two phototropins, phot1 and -2, act tog...

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confidence: 85%

Blue light regulates an auxin-induced K ⁺ -channel gene in the maize coleoptile

Fuchs¹,

Philippar²,

Ljung³

et al. 2003

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

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“…Recent results using modern techniques have supported this theory, including asymmetrical distribution of polar auxin transport carriers (Bennett et al, 1996;Chen et al, 1998;Friml et al, 2002) and molecular evidence for auxin asymmetry following gravity stimulation Muday et al, 1995;Lomax, 1997;Long et al, 2002;Ottenschlager et al, 2003). Lateral redistribution of radiolabeled indole-3-acetic acid (IAA) has been measured in both shoots (Parker and Briggs, 1990) and roots (Young et al, 1990;Young and Evans, 1996), and the redistribution of IAA has been shown to precede differential growth (Parker and Briggs, 1990). Other plant hormones, specifically brassinosteroids (Kim et al, 2000), ethylene (Lee et al, 1990;PhilosophHadas et al, 1996;Madlung et al, 1999), cytokinin (Golan et al, 1996), and gibberellic acid (Moore and Dickey, 1985;Rood et al, 1987;Brock and Kaufman, 1988;Chaban et al, 1999) have been shown to also play a role in gravitropism.…”

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confidence: 86%

The Fast and Transient Transcriptional Network of Gravity and Mechanical Stimulation in the Arabidopsis Root Apex

et al. 2004

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Plant root growth is affected by both gravity and mechanical stimulation . A coordinated response to both stimuli requires specific and common elements. To delineate the transcriptional response mechanisms, we carried out whole-genome microarray analysis of Arabidopsis root apices after gravity stimulation (reorientation) and mechanical stimulation and monitored transcript levels of 22,744 genes in a time course during the first hour after either stimulus. Rapid, transient changes in the relative abundance of specific transcripts occurred in response to gravity or mechanical stimulation, and these transcript level changes reveal clusters of coordinated events. Transcriptional regulation occurs in the root apices within less than 2 min after either stimulus. We identified genes responding specifically to each stimulus as well as transcripts regulated in both signal transduction pathways. Several unknown genes were specifically induced only during gravitropic stimulation (gravity induced genes). We also analyzed the network of transcriptional regulation during the early stages of gravitropism and mechanical stimulation.Plants adapt their growth in response to environmental cues. Gravity is a constant force that guides the direction of plant growth. Mechanical stimuli such as wind, rain, and obstacles in the soil trigger changes in growth patterns (Braam and Davis, 1990;. Gravitropic and mechanical stimulation in the root are interactive processes, mutually influencing differential growth (Mullen et al., 2000;Fasano et al., 2002;. The mechanisms of sensing and signal transduction for either stimulus are not well understood, but it has been shown that the transcript levels of specific genes are regulated early during signal transduction after either stimulus Braam and Davis, 1990).It is widely accepted that gravitropic stimulation by reorientation is perceived by sedimentation of starchcontaining plastids (statoliths) in the columella cells of the root tip (Kiss et al., 1989(Kiss et al., , 1996Juniper et al., 1966;Blancaflor et al., 1998). Columella cells show differences in their contribution toward gravity perception and in the velocity of sedimentation of their statoliths (Blancaflor et al., 1998). While complete sedimentation of the statoliths requires at least 5 min (Blancaflor et al., 1998;MacCleery and Kiss, 1999), the presentation time (duration of the stimulus that is required to establish a response) was estimated at only approximately 1 min for wild-type Arabidopsis root tips (Blancaflor et al., 1998). Statolith sedimentation is postulated to disrupt the actin-based cytoskeletal network and its links to plasma membrane receptors in some regions of the cell cortex (Yoder et al., 2001). Other groups hypothesized that statoliths are directly connected to the cytoskeleton, activating membrane proteins anchored to the filaments upon dislocation or activation of mechanosensitive ion channels (Evans et al., 1986;Pickard and Ding, 1993;Collings et al., 2001;Blancaflor, 2002).The transduction of the physical alt...

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“…The Cholodny-Went hypothesis, originally proposed in 1937, suggests that lateral transport of auxin across gravity-stimulated shoots may cause differential gravitropic growth (Evans, 1991;Trewavas, 1992). Lateral redistribution of radiolabeled indole-3-acetic acid (IAA) has been measured in both shoots (Parker and Briggs, 1990) and roots (Young et al, 1990), and the redistribution of IAA has been shown to precede differential growth and the gravity response (Parker and Briggs, 1990). Additionally, inhibition of auxin transport blocks root gravitropism (Muday and Haworth, 1994).…”

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Basipetal Auxin Transport Is Required for Gravitropism in Roots of Arabidopsis

et al. 2000

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Auxin transport has been reported to occur in two distinct polarities, acropetally and basipetally, in two different root tissues. The goals of this study were to determine whether both polarities of indole-3-acetic acid (IAA) transport occur in roots of Arabidopsis and to determine which polarity controls the gravity response. Global application of the auxin transport inhibitor naphthylphthalamic acid (NPA) to roots blocked the gravity response, root waving, and root elongation. Immediately after the application of NPA, the root gravity response was completely blocked, as measured by an automated video digitizer. Basipetal

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Transport of Indole-3-Acetic Acid during Gravitropism in Intact Maize Coleoptiles

Cited by 65 publications

References 17 publications

Blue light regulates an auxin-induced K ⁺ -channel gene in the maize coleoptile

Blue light regulates an auxin-induced K ⁺ -channel gene in the maize coleoptile

The Fast and Transient Transcriptional Network of Gravity and Mechanical Stimulation in the Arabidopsis Root Apex

Basipetal Auxin Transport Is Required for Gravitropism in Roots of Arabidopsis

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Transport of Indole-3-Acetic Acid during Gravitropism in Intact Maize Coleoptiles

Cited by 65 publications

References 17 publications

Blue light regulates an auxin-induced K + -channel gene in the maize coleoptile

Blue light regulates an auxin-induced K + -channel gene in the maize coleoptile

The Fast and Transient Transcriptional Network of Gravity and Mechanical Stimulation in the Arabidopsis Root Apex

Basipetal Auxin Transport Is Required for Gravitropism in Roots of Arabidopsis

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Blue light regulates an auxin-induced K ⁺ -channel gene in the maize coleoptile

Blue light regulates an auxin-induced K ⁺ -channel gene in the maize coleoptile