| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
First published online October 29, 2004; 10.1104/pp.104.053173 Plant Physiology 136:3616-3627 (2004) © 2004 American Society of Plant Biologists
Arabidopsis NAP and PIR Regulate Actin-Based Cell Morphogenesis and Multiple Developmental Processes1Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
The actin cytoskeleton mediates cellular processes through the dynamic regulation of the time, location, and extent of actin polymerization. Actin polymerization is controlled by several types of evolutionarily conserved proteins, including those comprising the ARP2/3 complex. In animal cells ARP2/3 activity is regulated by WAVE complexes that contain WAVE/SCAR proteins, PIR121, Nap125, and other proteins. The activity of the WAVE complex is regulated by Rho-GTPase-mediated signaling that leads to ARP2/3 activation by WAVE/SCAR proteins. We describe in this report Arabidopsis (Arabidopsis thaliana) genes encoding Nap and PIR proteins. Light-grown Atnap-1 and Atpir-1 mutant plants displayed altered leaf, inflorescence, silique, and seed set phenotypes. Dark-grown Atnap-1 and Atpir-1 seedlings also exhibited longer roots, enhanced skotomorphogenesis and Glc responses, and shorter thicker hypocotyls than those of wild type, showing that AtNAP and AtPIR participate in a variety of growth and developmental processes. Mutations in AtNAP and AtPIR caused cell morphology defects in cotyledon pavement cells and trichomes seen in mutants in ARP2/3 subunits and in plants expressing constitutively active Rop2 GTPase. The patterns and levels of actin polymerization observed in Atnap-1 and Atpir-1 mutant trichome cells and epidermal pavement cell morphology is consistent with Arabidopsis NAP and PIR proteins forming a WAVE complex that activates ARP2/3 activity. The multiple growth and developmental phenotypes of Atnap and Atpir mutants reveals these proteins are also required for a wider variety of cellular functions in addition to regulating trichome cell growth.
Reorganization of the actin cytoskeleton is required for many cell functions in a wide range of organisms. In animal cells extracellular signals often lead to dynamic changes in actin polymerization that alter cell morphology, movement, membrane dynamics, and other processes (Higgs and Pollard, 2001  ). Pharmacological and genetic studies have demonstrated that the actin cytoskeleton of plant cells plays an important role in a variety of cellular processes such as cell morphogenesis, stomatal closure, gravitropism, cell polarity and polarized cell growth, and cell division (Volkmann and Baluska, 1999; Vantard and Blanchoin, 2002; Deeks and Hussey, 2003).
The mechanisms regulating actin organization in plant cells are being revealed by genetic and cell biological analyses. Mutant alleles of ARP2/3 complex proteins, which nucleate the formation of networks of fine actin filaments, caused alterations in the expansion of epidermal pavement cell lobes and leaf trichomes and reduced coherence of the hypocotyl epidermis during cell expansion (Li et al., 2001
In animal cells actin polymerization is regulated via extracellular receptors that transduce signals to members of the Rho GTPase family such as Rac and cdc42 (Etienne-Manneville and Hall, 2002
Here we characterize two Arabidopsis genes encoding proteins similar to human Nap125 and PIR121 proteins. Analysis of insertion mutations in AtNAP and AtPIR genes revealed cell morphology defects in epidermal pavement cells and trichomes, and levels of F-actin filaments were reduced in trichome cells. These defects are consistent with AtNAP and AtPIR regulating ARP2/3 activity (Eden et al., 2002
Identification and Genetic Characterization of Arabidopsis AtNAP and AtPIR Genes Encoding Nap125- and PIR121-Like Proteins
The identification of the maize BRICK1 gene, encoding a plant protein related to animal HSPC300, suggested the existence of a WAVE-like regulatory complex in plants (Frank and Smith, 2002
To investigate the function of AtNAP and AtPIR, we obtained several insertion alleles from the SALK and GABI-Kat Arabidopsis T-DNA mutant collection (Fig. 2, A and B). Atnap-1 (SALK_038799), Atnap-2 (SALK_014298), Atnap-3 (SALK_135634), and Atnap-4 (SALK_009695) were isolated with a T-DNA insertion in the 18th intron, the 9th exon, the 10th exon, and the 21st exon, respectively (Fig. 2, A and C). Atpir-1 (GABI-Kat 313F03) and Atpir-2 (SALK_106757) were identified with T-DNA insertions in 6th intron and 5' untranslated region, respectively (Fig. 2, B and D). T-DNA insertions were confirmed by PCR using T-DNA specific and flanking primers and sequencing PCR products (Fig. 2, C and D). Northern-blot analysis revealed that neither the four Atnap mutant lines nor the two Atpir mutant lines had detectable transcripts of their respective genes (Fig. 2, E and F). These were therefore considered to be null mutant alleles.
All the Atnap and Atpir mutants exhibited similar defects in trichomes, epidermal cells, and seedling development (see below). The respective T-DNA insertions cosegregated with the defective trichome phenotypes in their F2 populations, demonstrating that the disruptions in AtNAP and AtPIR caused the mutant phenotypes observed. According to trichome phenotypes we observed that all the heterozygotic lines had the wild-type phenotype and the F2 population showed a segregation ratio of three wild type to one mutant, indicating that Atnap-1 and Atpir-1 are single recessive mutants (Table I). Progeny of crosses of the two lines with insertions in the AtPIR gene demonstrated the insertions were allelic, and crosses of the four lines with insertions in the AtNAP gene showed all these insertions were also allelic with respect to trichome phenotypes. This further confirmed that the insertions in AtNAP and AtPIR caused the trichome phenotypes.
Mutations in AtNAP and AtPIR Affect Growth and Development The effect of mutations in AtNAP and AtPIR on seedling development was investigated. No obvious differences in the strength of phenotype between Atnap-1, Atnap-2, Atnap-3, and Atnap-4 or between Atpir-1 and Atpir-2 were observed; therefore, we chose the Atnap-1 and Atpir-1 mutant lines for further characterization. Soil-grown Atnap-1 and Atpir-1 plants exhibited a variety of growth defects. The leaves of Atnap-1 and Atpir-1 mutants were paler green than those of wild type (Fig. 3A). This was due to reduced chlorophyll content (Fig. 3G). Leaf morphogenesis was also slightly altered compared to wild type. Wild-type rosette leaves, before bolting, were slightly epinastic, whereas the rosette leaves of Atnap-1 and Atpir-1 plants were flatter (Fig. 3A). The growth and development of siliques, seeds, and inflorescences was abnormal in Atnap-1 and Atpir-1 plants. Early developing siliques in mutant plants were straight and had a similar length to wild type. However, later-developing siliques were occasionally very short and contained fewer seeds (Fig. 3, C–F). The siliques in Atnap-1 and Atpir-1 contained slightly larger seed than wild type (data not shown). The inflorescences of Atnap-1 and Atpir-1 mutants continued indeterminate growth until senescence, in contrast to most wild-type inflorescences, which ceased flowering and elongation before senescence (Fig. 3, B and C).
Atnap-1 and Atpir-1 seedlings grown on vertical plates in the dark exhibited increased shoot development (Fig. 4, A–C). Wild-type seedlings grown for 15 d in the dark had partially expanded cotyledonary petioles, and true leaves had just started to develop (Fig. 4A). Dark-grown Atnap-1 and Atpir-1 plants had fully expanded cotyledonary petioles and the first true leaves had formed (Fig. 4, B and C). This increased dark development or skotomorphogenesis in mutants was not a result of earlier germination, since the germination of Atnap-1 and Atpir-1 seeds was the same as wild-type and mutant seed germinated with similar kinetics to wild-type seed (Fig. 4D). Furthermore, dark-grown Atnap-1 and Atpir-1 seedlings had shorter and thicker hypocotyls than wild type (Fig. 4, E and F), suggesting that AtNAP and AtPIR may regulate cell size and radial expansion of hypocotyls. Interestingly, hypocotyl elongation of Atnap-1 and Atpir-1 mutants showed enhanced responses to sugar in the dark. Wild-type Columbia (Col) seedlings do not exhibit significant hypocotyl elongation in response until Glc levels are between 0.1% and 0.5%, and hypocotyl elongation is only inhibited at Glc concentrations above 3% (data not shown). In contrast, both Atnap-1 and Atpir-1 seedlings had longer hypocotyls than wild type at low Glc levels, and at higher Glc concentrations hypocotyls were shorter than wild type (Fig. 4G). This suggested the mutants seedlings displayed Glc-hypersensitive hypocotyl elongation. Finally, roots of dark-grown Atnap-1 and Atpir-1 were substantially longer than that of wild type (Fig. 4H).
Atnap-1 and Atpir-1 Plants Exhibit Defects in Epidermal Cell Morphogenesis
The effect of the Atnap-1 and Atpir-1 mutations on trichome development was examined because mutations in the ARP2/3 complex of Arabidopsis exhibit distorted trichomes. Wild-type Arabidopsis trichomes generally form three branches, the position, shape, and length of which are tightly regulated during trichome development (Huelskamp et al., 1994
Since the maize brick and Arabidopsis arp2/3 subunit mutants have defects in epidermal cell lobing, we examined pavement cell shape and size in the Atnap-1 and Atpir-1 mutants. Mature pavement cells on the adaxial surface of wild-type cotyledons have regular lobes that interlock tightly with adjacent cells. In Atnap-1 and Atpir-1 mutants lobe shape was indistinguishable from wild type (Fig. 5, M–O). However, some cotyledon pavement cells failed to tessellate normally, resulting in gaps between adjacent cells (Fig. 5, M–O). These gaps were not observed in true leaves.
As the Atnap-1 and Atpir-1 mutants affected trichome development, and because related genes are involved in regulating the actin cytoskeleton in animal cells, we visualized the actin cytoskeleton of Atnap-1 and Atpir-1 trichomes using fluorochrome-conjugated phalloidin. We compared the actin cytoskeleton in the Atnap-1 and Atpir-1 mutants with an arp3 mutant to determine any similarities between these mutants. During stage 2 trichome development, the trichome stalks elongate, and during stage 3 rudimentary branches develop (Szymanski et al., 1999
To quantify these observations we measured the ratio of subcortical (core) actin to total actin abundance in trichome branches in wild-type Col, arp3, Atnap-1, and Atpir-1 mutants. In stage 4/5 trichome branches the average ratio of core to total actin in arp3 mutants was significantly reduced (0.39 ± SE 0.03), compared to wild type (0.46 ± SE 0.02; Fig. 6M). In Atnap-1 and Atpir-1 stage 4/5 branches the average ratio of core to total actin including all data points was 0.45 ± SE 0.03 and 0.47 ± SE 0.02, respectively (Fig. 6M). Although this was similar to wild type we found that actin distribution in the trichomes of Atnap-1 and Atpir-1 formed two distinct groups. Compared to wild type approximately two-thirds of Atnap-1 (n = 14) and Atpir-1 (n = 17) branches (Fig. 6M, black circles) have reduced relative amounts of core actin, 0.40 ± SE 0.01 and 0.42 ± SE 0.02, respectively. The remaining Atnap-1 (n = 5) and Atpir-1 (n = 6) branches (Fig. 6M, white circles) have on average slightly increased relative amounts of core actin, 0.63 ± SE 0.02 and 0.62 ± SE 0.00, respectively.
Levels of AtNAP and AtPIR mRNA were analyzed in various tissues by RNA gel-blot analysis. Figure 7A shows that AtNAP and AtPIR transcripts were detected in all tissues examined, including young seedlings, roots, stems, rosette leaves, and flowers. AtNAP mRNA levels were highest in roots. The spatial expression patterns of AtNAP and AtPIR were revealed by histochemical assays of
A survey of the Arabidopsis genome for proteins that may regulate ARP2/3 activity identified two proteins encoded by At2g35110 and At5g18410 with significant overall similarity to human, Drosophila, and C. elegans Nap125 and PIR121 proteins, respectively. The preservation of identity and frequent conserved substitutions throughout the Arabidopsis, human, Drosophila, and C. elegans proteins suggested these Arabidopsis proteins may perform similar cellular functions to their animal counterparts. After submission of this study, several related studies describing the identification and initial characterization AtNAP and AtPIR were also published (Basu et al., 2004 ; Brembu et al., 2004; Deeks et al., 2004; El-Assal Sel et al., 2004). These studies report similar effects of mutations in AtNAP and AtPIR on the actin cytoskeleton to those described here, and also showed interactions between AtNAP and AtPIR and between AtPIR and AtROP2 (Basu et al., 2004). Furthermore, Arabidopsis proteins similar to SCAR proteins were also reported (Brembu et al., 2004; Deeks et al., 2004). The C-terminal VCA motif of these proteins, which is common to both WAVE/SCAR and WASP proteins, drives conformational changes in the ARP2/3 complex that promote actin nucleation and the VCA domain of the Arabidopsis SCAR protein encoded by At2g34150 was shown to bind actin in vitro (Deeks et al., 2004). These analyses, together with the characterization of BRICK/HSPC300 proteins (Frank and Smith, 2002) and SPIKE1 (Qiu et al., 2002) that are related to other known components of animal WAVE complexes, provide initial evidence for Arabidopsis WAVE complexes that regulate actin cytoskeleton dynamics. Trichome development was strongly affected in the Atnap and Atpir mutants; they exhibited frequent swollen trunks bearing second and third branches much reduced in length. Related distorted trichome phenotypes result from overexpression of CA-rop2 in Arabidopsis (Fu et al., 2002). Mutations of subunits of the ARP2/3 complex also lead to characteristic distorted trichomes with short distended branches and a bulbous base (Mathur and Chua, 2000; Le et al., 2003; S. Li et al., 2003; Mathur et al., 2003a). Among the distorted trichome class of mutants, no fewer than four encode subunits of the ARP2/3 complex (Deeks and Hussey, 2003; Smith and Li, 2004), indicating that proteins regulating the actin cytoskeleton cause distorted trichomes. Recently the gnarled locus was shown to be allelic to Atnap mutants (Brembu et al., 2004; El-Assal Sel et al., 2004), and Atpir was reported to be allelic to klunker (Mutondo et al., 2004). However, this finding is currently inconsistent with another report claiming Atpir mutants are not allelic to klunker (Basu et al., 2004). Despite this apparent difference it is likely that other distorted mutants may also encode cytoskeletal regulators.
Reduced cell polarity in ARP2/3 mutants has been proposed to underlie these changes in trichome cell shape, suggesting that cell polarity may be altered in the Atnap and Atpir mutants. This is supported by the observation of reduced tessellation and gaps between epidermal pavement cells in Atnap and Atpir cotyledons. This is also seen in ARP2/3 mutants and is thought to be due to reduced cell lobing. Similar observations have also been made recently for Atpir mutants (Basu et al., 2004
The severity of trichome branch distortion in arp3, Atnap, and Atpir mutant plants correlated with the degree of disruption in F-actin cable organization. In more disrupted trichomes, actin cables were randomly arranged into a mesh-like structure in all three mutants compared to wild-type trichomes. Measurement of the distribution of F-actin showed that most trichome branches of the arp3 mutant had reduced core F-actin in proportion to total actin filaments. About two-thirds of stage 4/5 Atnap-1 and Atpir-1 mutant trichome branches also showed a reduction in core F-actin. The remaining one-third of Atnap-1 and Atpir-1 trichome branches had slightly elevated ratios of core actin filaments to total actin levels that were not clearly related to the degree of trichome branch distortion. The reduced levels of core actin filaments seen in the majority of mutant trichomes was also seen in related studies (Basu et al., 2004
Current evidence obtained from studies in human, Dictyostelium, and Drosophila cells supports two distinct mechanisms of WAVE function (Stradal et al., 2004
We have also identified a wider range of developmental and growth defects in the Atnap and Atpir mutants. These include low chlorophyll levels, leaf epinasty, reduced seed set, deformed siliques, and enhanced responses to Glc, root growth, and skotomorphogenesis. This range of phenotypes is consistent with the widespread expression patterns of the AtNAP and AtPIR genes. In contrast, mutations in ARP2/3 subunits are reported to be restricted to altered morphogenesis of trichome and epidermal cells (Le et al., 2003
Database Search and Bioinformatics To identify Arabidopsis (Arabidopsis thaliana) proteins related to members of the WAVE complex, human, Drosophila, and Dictyostelium WAVE complex members were used as queries for BLASTP and TBLASTN searches of the National Center for Biotechnology Information database (www.ncbi.nlm.nil.gov) and the Arabidopsis Information Resource database (www.arabdopsis.org). Amino acid alignment was conducted using ClustalW (www.ebi.ac.uk/clustalw) and Bioedit.
To identify cDNA sequences of AtNAP and AtPIR, we performed reverse transcription (RT)-PCR using AtNAP and AtPIR specific primers and sequenced RT-PCR products. Total RNA was extracted from Arabidopsis seedlings using an RNeasy Plant Mini kit (Qiagen, West Sussex, UK) according to the kit manual. RT-PCR analysis was performed as described (Y. Li et al., 2003
All experiments described in this study involve Arabidopsis ecotype Col-0. Atnap-1 (SALK_038799), Atnap-2 (SALK_014298), Atnap-3 (SALK_135634), Atnap-4 (SALK_009695), Atpir-2 (SALK_106757), and Atpir-1 (GABI-Kat 313F03) lines were identified in the AtIDB database (www.atidb.org) and obtained from the Nottingham Arabidopsis Stock Centre or GABI-Kat. Seeds were surface-sterilized with 100% isopropanol and 20% (v/v) household bleach, washed at least five times with sterile water, stratified at 4°C for 6 d in the dark, and germinated on Murashige and Skoog medium (Duchefa Biochemie BV, Haarlem, The Netherlands) supplemented with 0.9% agar and 1% Glc. Seedlings were grown in media under continuous light at 22°C and grown in soil under 16-h light periods at 20°C to 25°C.
Arabidopsis genomic DNA preparation was performed as described (Qian et al., 2001
Total RNA was extracted from Arabidopsis seedlings, roots, stems, leaves, and flowers using an RNeasy Plant Mini kit (Qiagen) according to the manual. RNA gel-blot analysis was performed as described (Rook et al., 2001
Seedlings grown for 9 d in constant light were frozen in nitrogen slush at –190°C. Ice was sublimed at –90°C, and the specimen was sputter coated and examined on an XL 30 FEG (Philips, Eindhoven, The Netherlands) cryoscanning electron microscope fitted with a cold stage.
To visualize actin in trichomes, young leaves were incubated in 2% formaldehyde in PEM buffer (100 mM PIPES, 5 mM EGTA, 4 mM MgCl2, 100 mM mannitol, and 0.01% IGEPAL) for 30 min. Tissue was washed three times in PEM buffer before incubation overnight in PEM buffer and 0.8 units Alexa Fluor 488-phalloidin (Molecular Probes, Leiden, The Netherlands). F-actin was visualized using a Leica (Wetzlar, Germany) SP confocal microscope and images were analyzed with Leica Confocal Software. Stage 4/5 branches were between 16 µm and 50 µm. Measurements were taken only from trichomes where all branches were less than 50 µm. The average branch length of col, arp3, Atnap-1, and Atpir-1 was 25 µm, 32 µm, 35 µm and 33 µm respectively. ImageJ software was used for measuring integrated fluorescence intensity of transverse sections taken at the midpoint of the branch. The core fluorescence was within a region 2.5 µm from the cell surface. Seven branches for wild type, 12 branches for arp3, 14 branches for Atnap-1, and 18 branches for Atpir-1 were measured.
The AtNAP promoter-GUS construct (AtNAP::GUS) and the AtPIR promoter-GUS construct (AtPIR::GUS) were made using a PCR-based Gateway system. The promoter specific primers for the AtNAP gene were NAPP-F (5'-CACCAGCCGAGTACAAAGAAGAAGC-3') and NAPP-R (5'-TAATTCAGTACAATAATCTCTACAATA-3') and for the AtPIR gene were PIRP-F (5'-CACCCATCAGCCTTGCCCGTATAGC-3') and PIRP-R (5'-TGAGTCACCTGGAAAGATCAG-3'). PCR products were subcloned into pENTR/D-TOPO using TOPO enzyme and sequenced. Then the AtNAP and AtPIR promoters were further subcloned into Gateway Binary Vector (pGWB3) containing the GUS reporter gene. Arabidopsis transformation was made by dipping method using Agrobacterium strain GV3101. Transformants were selected on kanamycin (50 µg/mL) medium. Seedlings were stained in a solution of 1 mM X-gluc, 50 mM NaPO4 buffer, 0.4 mM each K3Fe(CN)6/K4Fe(CN)6, 0.1% (v/v) Triton X-100 and incubated at 37°C for 10 to 24 h. After GUS staining chlorophyll was removed using 70% ethanol. Sequence data from this article have been deposited with the EMBL/GenBank data libraries under accession numbers AY787211 and AY787212.
We thank Kim Findlay for assistance with scanning electron microscopy, the Nottingham Arabidopsis Stock center (NASC) for mutant lines, and members of the Bevan group for advice. Received September 9, 2004; returned for revision September 30, 2004; accepted September 30, 2004.
1 This work was supported by the Biotechnology and Biological Sciences Research Council (grant no. 208/EGM16126), by Syngenta (grant no. PMC19), and by the John Innes Centre Core Strategic Grant (to M.W.B.). 
2 These authors contributed equally to the paper. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.053173. * Corresponding author; e-mail michael.bevan{at}bbsrc.ac.uk; fax 01603–450025.
Basu D, El-Assal Sel D, Le J, Mallery EL, Szymanski DB (2004) Interchangeable functions of Arabidopsis PIROGI and the human WAVE complex subunit SRA1 during leaf epidermal development. Development 131: 4345–4355 Blagg SL, Stewart M, Sambles C, Insall RH (2003) PIR121 regulates pseudopod dynamics and SCAR activity in Dictyostelium. Curr Biol 13: 1480–1487[CrossRef][ISI][Medline]
Bogdan S, Klambt C (2003) Kette regulates actin dynamics and genetically interacts with Wave and Wasp. Development 130: 4427–4437
Brembu T, Winge P, Seem M, Bones AM (2004) NAPP and PIRP encode subunits of a putative wave regulatory protein complex involved in plant cell morphogenesis. Plant Cell 16: 2335–2349
Cheung AY, Wu HM (2004) Overexpression of an Arabidopsis formin stimulates supernumerary actin cable formation from pollen tube cell membrane. Plant Cell 16: 257–269 Deeks MJ, Hussey PJ (2003) Arp2/3 and ‘The Shape of things to come’. Curr Opin Plant Biol 6: 561–567[CrossRef][ISI][Medline] Deeks MJ, Kaloriti D, Davies B, Malho R, Hussey PJ (2004) Arabidopsis NAP1 is essential for Arp2/3-dependent trichome morphogenesis. Curr Biol 14: 1410–1414[CrossRef][ISI][Medline] Eden S, Rohatgi R, Podtelejnikov AV, Mann M, Kirschner MW (2002) Mechanism of regulation of WAVE1-induced actin nucleation by Rac1 and Nck. Nature 418: 790–793[CrossRef][Medline] El-Assal Sel D, Le J, Basu D, Mallery EL, Szymanski DB (2004) Arabidopsis GNARLED encodes a NAP125 homolog that positively regulates ARP2/3. Curr Biol 14: 1405–1409[CrossRef][ISI][Medline] Etienne-Manneville S, Hall A (2002) Rho GTPases in cell biology. Nature 420: 629–635[CrossRef][Medline]
Frank MJ, Cartwright HN, Smith LG (2003) Three Brick genes have distinct functions in a common pathway promoting polarized cell division and cell morphogenesis in the maize leaf epidermis. Development 130: 753–762 Frank MJ, Smith LG (2002) A small, novel protein highly conserved in plants and animals promotes the polarized growth and division of maize leaf epidermal cells. Curr Biol 12: 849–853[CrossRef][ISI][Medline]
Fu Y, Li H, Yang Z (2002) The ROP2 GTPase controls the formation of cortical fine F-actin and the early phase of directional cell expansion during Arabidopsis organogenesis. Plant Cell 14: 777–794 Higgs HN, Pollard TD (2001) Regulation of actin filament network formation through ARP2/3 complex: activation by a diverse array of proteins. Annu Rev Biochem 70: 649–676[CrossRef][ISI][Medline] Huelskamp M, Misera S, Juergens G (1994) Genetic dissection of trichome cell development in Arabidopsis. Cell 76: 555–566[CrossRef][ISI][Medline]
Hummel T, Leifker K, Klambt C (2000) The Drosophila HEM-2/NAP1 homolog KETTE controls axonal pathfinding and cytoskeletal organization. Genes Dev 14: 863–873 Ketelaar T, Allwood EG, Anthony R, Voigt B, Menzel D, Hussey PJ (2004) The actin-interacting protein AIP1 is essential for actin organization and plant development. Curr Biol 14: 145–149[CrossRef][ISI][Medline] Kunda P, Craig G, Dominguez V, Baum B (2003) Abi, Sra1, and Kette control the stability and localization of SCAR/WAVE to regulate the formation of actin-based protrusions. Curr Biol 13: 1867–1875[CrossRef][ISI][Medline] Le J, El-Assal Sel D, Basu D, Saad ME, Szymanski DB (2003) Requirements for Arabidopsis ATARP2 and ATARP3 during epidermal development. Curr Biol 13: 1341–1347[CrossRef][ISI][Medline]
Li H, Shen JJ, Zheng ZL, Lin Y, Yang Z (2001) The Rop GTPase switch controls multiple developmental processes in Arabidopsis. Plant Physiol 126: 670–684
Li S, Blanchoin L, Yang Z, Lord EM (2003) The putative Arabidopsis arp2/3 complex controls leaf cell morphogenesis. Plant Physiol 132: 2034–2044
Li Y, Qian Q, Zhou Y, Yan M, Sun L, Zhang M, Fu Z, Wang Y, Han B, Pang X, et al (2003) BRITTLE CULM1, which encodes a COBRA-like protein, affects the mechanical properties of rice plants. Plant Cell 15: 2020–2031
Mathur J, Chua NH (2000) Microtubule stabilization leads to growth reorientation in Arabidopsis trichomes. Plant Cell 12: 465–477
Mathur J, Mathur N, Kernebeck B, Hulskamp M (2003a) Mutations in actin-related proteins 2 and 3 affect cell shape development in Arabidopsis. Plant Cell 15: 1632–1645
Mathur J, Mathur N, Kirik V, Kernebeck B, Srinivas BP, Hulskamp M (2003b) Arabidopsis CROOKED encodes for the smallest subunit of the ARP2/3 complex and controls cell shape by region specific fine F-actin formation. Development 130: 3137–3146 Mullins RD (2000) How WASP-family proteins and the Arp2/3 complex convert intracellular signals into cytoskeletal structures. Curr Opin Cell Biol 12: 91–96[CrossRef][ISI][Medline] Mutondo M, Zimmerman I, Saedler H, Huelskamp M (2004) The Arabidopsis KLUNKER gene encodes a putative regulator of the ARP2/3 complex (abstract no. T03-039). In 15th International Conference Arabidopsis Research, July 11–14, 2004, Berlin Qian Q, Li YH, Zeng D, Teng S, Wang Z, Li X, Dong Z, Dai N, Sun L, Li J (2001) Isolation and genetic characterization of a fragile plant mutant rice (Oryza sativa L.). Chin Sci Bull 46: 2082–2085
Qiu JL, Jilk R, Marks MD, Szymanski DB (2002) The Arabidopsis SPIKE1 gene is required for normal cell shape control and tissue development. Plant Cell 14: 101–118
Ramachandran S, Christensen HE, Ishimaru Y, Dong CH, Chao-Ming W, Cleary AL, Chua NH (2000) Profilin plays a role in cell elongation, cell shape maintenance, and flowering in Arabidopsis. Plant Physiol 124: 1637–1647
Rogers SL, Wiedemann U, Stuurman N, Vale RD (2003) Molecular requirements for actin-based lamella formation in Drosophila S2 cells. J Cell Biol 162: 1079–1088 Rook F, Corke F, Card R, Munz G, Smith C, Bevan MW (2001) Impaired sucrose-induction mutants reveal the modulation of sugar-induced starch biosynthetic gene expression by abscisic acid signalling. Plant J 26: 421–433[CrossRef][ISI][Medline]
Schumacher K, Vafeados D, McCarthy M, Sze H, Wilkins T, Chory J (1999) The Arabidopsis det3 mutant reveals a central role for the vacuolar H(+)-ATPase in plant growth and development. Genes Dev 13: 3259–3270 Smith LG, Li R (2004) Actin polymerization: riding the wave. Curr Biol 14: R109–R111[CrossRef][Medline]
Soto MC, Qadota H, Kasuya K, Inoue M, Tsuboi D, Mello CC, Kaibuchi K (2002) The GEX-2 and GEX-3 proteins are required for tissue morphogenesis and cell migrations in C. elegans. Genes Dev 16: 620–632 Stradal TE, Rottner K, Disanza A, Confalonieri S, Innocenti M, Scita G (2004) Regulation of actin dynamics by WASP and WAVE family proteins. Trends Cell Biol 14: 303–311[CrossRef][ISI][Medline]
Szymanski DB, Marks MD, Wick SM (1999) Organized F-actin is essential for normal trichome morphogenesis in Arabidopsis. Plant Cell 11: 2331–2347 Vantard M, Blanchoin L (2002) Actin polymerization processes in plant cells. Curr Opin Plant Biol 5: 502–506[CrossRef][ISI][Medline] Volkmann D, Baluska F (1999) Actin cytoskeleton in plants: from transport networks to signaling networks. Microsc Res Tech 47: 135–154[CrossRef][ISI][Medline] Wasteneys GO, Galway ME (2003) Remodeling the cytoskeleton for growth and form: an overview with some new views. Annu Rev Plant Biol 54: 691–722[CrossRef][Medline] This article has been cited by other articles:
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
TOP
ABSTRACT
RESULTS
-glucuronidase (GUS) activity of transgenic plants containing AtNAP promoter:GUS fusions (AtNAP::GUS) or AtPIR promoter:GUS fusions (AtPIR::GUS). Histochemical staining shows AtNAP and AtPIR gene expression throughout the plant, including roots, root hairs, hypocotyls, cotyledons, true leaves, trichomes, and flowers (
