The Organization of the Actin Cytoskeleton in Vertical and Graviresponding Primary Roots of Maize

Blancaflor, Elison B.; Hasenstein, Karl H.

doi:10.1104/pp.113.4.1447

Cited by 72 publications

(54 citation statements)

References 38 publications

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“…The latter point is especially important in light of the postulated function of the actomyosin system (Volkmann et al, 1993;Baluška and Hasenstein, 1997). As has been demonstrated earlier, the disruption of actin did not reduce gravisensing (Blancaflor and Hasenstein, 1997;Yamamoto and Kiss, 2002) but interfered with the termination of the graviresponse (Hou et al, 2004) and inhibited amyloplasts sedimentation (Palmieri and Kiss, 2005). Similar to these reports, our data indicate that actin is not required for the establishment of gravisensing because germination in the presence of a high concentration of Lat B did not delay the onset of gravisensing (Fig.…”

Section: Discussionsupporting

confidence: 78%

“…5) long after gravicompetency was established. Although staining of F-actin in columella cells is difficult, the data support the Lat B results that gravisensing occurs in the absence of F-actin (Blancaflor and Hasenstein, 1997;Palmieri and Kiss, 2005). Because of the seed orientation along the edge of the germination paper (see ''Materials and Methods''), the emerging root did not contact the substrate and therefore cannot take up Lat B.…”

Section: Discussionsupporting

confidence: 64%

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The Onset of Gravisensitivity in the Embryonic Root of Flax

Hasenstein

2005

Plant Physiology

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Vertical orientation of emerging roots typically is the first response of plants to gravity. Although root gravitropism has been studied extensively, no conclusive data on the onset of gravisensing exist. We determined the inception of gravisensitivity in flax (Linum usitatissimum) roots by clinorotating germinating seeds after various periods of static orientation (gravistimulation) of imbibed seeds. Gravitropic competency was established about 8 h after imbibition, 11 h prior to germination. The time was determined based on 50% of the newly emerged roots curving in the direction of the gravity vector during static imbibition, despite subsequent clinorotation. The threshold value was affected by the orientation of the seeds. Upward orientation of the micropyle/radicle reduced the number of graviresponding roots to about one-half. Prolonged clinorotation weakened the graviresponse. Gravisensing was accompanied by the development of amyloplasts, but the actin cytoskeleton was not involved because imbibition in Latrunculin B did not affect the onset of gravisensitivity or germination, and the development of F-actin in untreated controls was observed only after the onset of gravisensitivity.

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Section: Discussionsupporting

confidence: 78%

Section: Discussionsupporting

confidence: 64%

The Onset of Gravisensitivity in the Embryonic Root of Flax

Hasenstein

2005

Plant Physiology

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“…In the tip-growing pollen tube, F-actin arrays are very dynamic, changing from large spherical bodies to F-actin bundles oriented predominantly parallel to the growth axis (Tiwari and Polito, 1988). Similar F-actin arrays were also found for root hair growth (Miller et al, 1999) as well as root tip growth (Blancaflor and Hasenstein, 1997). However, Arabidopsis act7 mutants showed remarkably reduced F-actin in the cells of the root elongation zone.…”

Section: Ghact1 Plays a Major Role In Fiber Elongationmentioning

confidence: 61%

The Cotton ACTIN1 Gene Is Functionally Expressed in Fibers and Participates in Fiber Elongation

et al. 2005

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Single-celled cotton fiber (Gossypium hirsutum) provides a unique experimental system to study cell elongation. To investigate the role of the actin cytoskeleton during fiber development, 15 G. hirsutum ACTIN (GhACT) cDNA clones were characterized. RNA gel blot and real-time RT-PCR analysis revealed that GhACT genes are differentially expressed in different tissues and can be classified into four groups. One group, represented by GhACT1, is expressed predominantly in fiber cells and was studied in detail. A 0.8-kb GhACT1 promoter sufficient to confirm its fiber-specific expression was identified. RNA interference of GhACT1 caused significant reduction of its mRNA and protein levels and disrupted the actin cytoskeleton network in fibers. No defined actin network was observed in these fibers and, consequently, fiber elongation was inhibited. Our results suggested that GhACT1 plays an important role in fiber elongation but not fiber initiation

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“…Although inhibition studies have not detected a role for the actin cytoskeleton in the gravity response of roots (Blancaflor and Hasenstein, 1997;Staves et al, 1997;Godbole et al, 2000), recent isolation of several mutants has suggested a connection. The arg1 mutant has a defect in a gene encoding a protein with a DnaJ domain, which is used by a number of proteins that interact with the cytoskeleton (Sedbrook et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

Mutations in the Gravity Persistence Signal Loci in Arabidopsis Disrupt the Perception and/or Signal Transduction of Gravitropic Stimuli

et al. 2002

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Gravity plays a fundamental role in plant growth and development, yet little is understood about the early events of gravitropism. To identify genes affected in the signal perception and/or transduction phase of the gravity response, a mutant screen was devised using cold treatment to delay the gravity response of inflorescence stems of Arabidopsis. Inflorescence stems of Arabidopsis show no response to gravistimulation at 4°C for up to 3 h. However, when gravistimulated at 4°C and then returned to vertical at room temperature (RT), stems bend in response to the previous, horizontal gravistimulation (H. Fukaki, H. Fujisawa, M. Tasaka [1996] Plant Physiology 110: 933-943). This indicates that gravity perception, but not the gravitropic response, occurs at 4°C. Recessive mutations were identified at three loci using this cold effect on gravitropism to screen for gravity persistence signal (gps) mutants. All three mutants had an altered response after gravistimulation at 4°C, yet had phenotypically normal responses to stimulations at RT. gps1-1 did not bend in response to the 4°C gravity stimulus upon return to RT. gps2-1 responded to the 4°C stimulus but bent in the opposite direction. gps3-1 over-responded after return to RT, continuing to bend to an angle greater than wild-type plants. At 4°C, starch-containing statoliths sedimented normally in both wild-type and the gps mutants, but auxin transport was abolished at 4°C. These results are consistent with GPS loci affecting an aspect of the gravity signal perception/transduction pathway that occurs after statolith sedimentation, but before auxin transport.Gravity is a constant stimulus governing the orientation of plant growth. In response to changes in the gravity vector, plants reorient by differential growth. When placed horizontally, shoots and roots of a plant exhibit asymmetric growth resulting in upward or downward curvature, respectively. Gravitropism is only one part of a complex response network that integrates information from developmental and environmental stimuli (Ramussen, 1995). For simplicity, the response pathway has been separated into three sequential steps: gravity perception, signal transduction, and asymmetric growth response (for review, see Sack, 1991). The first step in gravity perception is the sedimentation of amyloplasts in shoots and roots (Sack, 1991;Kiss, 2000;Weise et al., 2000).Later aspects of the gravity response are driven by the asymmetric distribution of auxin that is thought to induce the differential growth that is required for gravitropic curvature (for review, see Muday, 2001). What is much less clear are the mechanisms by which statolith sedimentation initiates the transduction of the gravitropic signal and directs the asymmetric distribution of auxin.Arabidopsis has emerged as a powerful genetic model and has been useful in the dissection of the molecular mechanisms of the gravity response (Tasaka et al., 1999;Chen et al., 2002). Arabidopsis mutants with gravitropic response defects specific to the inflorescence stem, ...

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The Organization of the Actin Cytoskeleton in Vertical and Graviresponding Primary Roots of Maize

Cited by 72 publications

References 38 publications

The Onset of Gravisensitivity in the Embryonic Root of Flax

The Onset of Gravisensitivity in the Embryonic Root of Flax

The Cotton ACTIN1 Gene Is Functionally Expressed in Fibers and Participates in Fiber Elongation

Mutations in the Gravity Persistence Signal Loci in Arabidopsis Disrupt the Perception and/or Signal Transduction of Gravitropic Stimuli

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