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First published online December 11, 2003; 10.1105/tpc.014407 American Society of Plant Biologists SETH1 and SETH2, Two Components of the Glycosylphosphatidylinositol Anchor Biosynthetic Pathway, Are Required for Pollen Germination and Tube Growth in Arabidopsis
a Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom
Glycosylphosphatidylinositol (GPI) anchoring provides an alternative to transmembrane domains for anchoring proteins to the cell surface in eukaryotes. GPI anchors are synthesized in the endoplasmic reticulum via the sequential addition of monosaccharides, fatty acids, and phosphoethanolamines to phosphatidylinositol. Deficiencies in GPI biosynthesis lead to embryonic lethality in animals and to conditional lethality in eukaryotic microbes by blocking cell growth, cell division, or morphogenesis. We report the genetic and phenotypic analysis of insertional mutations disrupting SETH1 and SETH2, which encode Arabidopsis homologs of two conserved proteins involved in the first step of the GPI biosynthetic pathway. seth1 and seth2 mutations specifically block male transmission and pollen function. This results from reduced pollen germination and tube growth, which are associated with abnormal callose deposition. This finding suggests an essential role for GPI anchor biosynthesis in pollen tube wall deposition or metabolism. Using transcriptomic and proteomic approaches, we identified 47 genes that encode potential GPI-anchored proteins that are expressed in pollen and demonstrated that at least 11 of these proteins are associated with pollen membranes by GPI anchoring. Many of the identified candidate proteins are homologous with proteins involved in cell wall synthesis and remodeling or intercellular signaling and adhesion, and they likely play important roles in the establishment and maintenance of polarized pollen tube growth.
Glycosylphosphatidylinositol (GPI) membrane anchors provide an alternative to transmembrane domains for anchoring proteins to the cell surface in eukaryotes. GPI anchoring can confer localized or polarized targeting and therefore can dramatically alter the functional properties of proteins. In animals, GPI-anchored proteins (GAPs) include a broad range of cell surface proteins, such as enzymes, receptors, complement regulators, and adhesion molecules (Ikezawa, 2002  ). In plants, GAPs form a relatively abundant class of proteins present in the plasma membrane (Sherrier et al., 1999). Many of the demonstrated and predicted Arabidopsis GAPs show similarity to characterized cell surface proteins as diverse as  -1,3-glucanases, metalloproteases and aspartylproteases, glycerophosphodiesterases, phytocyanins, multi-copper oxidases, extensins, classic arabinogalactan proteins, plasma membrane receptors, peptides, and lipid transfer–like proteins (Borner et al., 2002, 2003).
To date, only 4 of the 248 predicted Arabidopsis GAPs (Borner et al., 2002
GPI anchors are synthesized in the endoplasmic reticulum via the sequential addition of monosaccharides, fatty acids, and phosphoethanolamines to phosphatidylinositol (reviewed by Schultz et al., 2000
GPI biosynthetic pathways have been studied extensively in animals and microbes and are a target for the development of parasite-specific therapeutic agents. Deficiencies in GPI biosynthesis lead to embryonic lethality in animals and to conditional lethality in eukaryotic microbes by blocking cell growth, cell division, or morphogenesis. Although mammalian cells can survive in culture without GPI anchors, partial deficiency at different steps of the GPI biosynthetic pathway can have drastic effects in whole animals or in eukaryotic microbes. In human, an X-linked mutation of PIG-A in hematopoietic stem cells leads to paroxysmal nocturnal hemoglobinuria, an acquired clonal disease (Rosti, 2000 Here, we report the genetic and phenotypic analysis of insertional mutations disrupting the SETH1 and SETH2 genes that encode homologs of PIG-C and PIG-A, respectively, two components of the GPI-GnT complex. Heterozygous GPI biosynthetic knockout mutations in Arabidopsis have no effect on sporophytic development and megagametogenesis but show male gametophyte–specific effects that almost completely block transmission through pollen. GPI-deficient pollen grains develop normally and are viable at pollination but show reduced germination and pollen tube growth. To provide a genome-wide view of GAPs expressed in pollen, we used both transcriptomic and proteomic approaches. We identified 47 genes whose transcripts were expressed in mature pollen and that encode probable GAPs. Eleven of these proteins were confirmed to be associated with pollen membranes through GPI anchoring. Our data suggest that pollen-expressed GAPs fulfill essential functions in pollen germination and tube growth.
seth1 Insertional Mutations Specifically Block Male Gametophytic Transmission From a genetic screen of 3616 DsE and DsG transposon lines based on marker segregation ratio distortion, we isolated 19 independent gametophytic mutations (E. Lalanne, C. Michaelidis, A. Johnson, R. Patel, R. Howden, J. Moore, W. Gagliano, J.P. Vielle Calzada, U. Grossniklaus, and D. Twell, unpublished data), including an insertion, seth1-1, that disrupts a putative phosphatidylinositol-glycan synthase subunit C gene. Two additional insertional alleles, seth1-2 and seth1-3, were identified in the Syngenta collection (Sessions et al., 2002 ). Heterozygous seth1 insertions had no effect on sporophytic development, and no homozygous mutant plants were identified by segregation analysis of progeny from >500 plants derived from seth1-1 heterozygotes. Analysis of self-progeny revealed that all three seth1 alleles segregated 1:1 for the marker within the insertion, suggesting reduced transmission of the gametes harboring the insertion (Table 1). Progeny testing revealed strict cosegregation of antibiotic or herbicide resistance with the reduced genetic transmission phenotype for all three seth1 alleles (data not shown). Genetic transmission of seth1 mutations through the male and female gametes was determined in reciprocal test crosses of heterozygous mutants and wild-type plants. The transmission efficiency of the mutant allele describes the fraction of mutant alleles that are transmitted successfully to the progeny (Howden et al., 1998). Female transmission was normal, but there was almost no transmission (transmission efficiency < 1%) of seth1 alleles through the male, demonstrating that all three seth1 mutations specifically affect male gametophyte development and/or functions (Table 1).
In the three seth1 insertion lines, the DsG transposon (seth1-1) or T-DNAs (seth1-2 and seth1-3) was inserted into the single exon of At2g34980 (SETH1) (Figure 1A). SETH1 encodes a protein that is 31.6% identical (52.7% similar) over 296 amino acids to human PIG-C (HsPIGC). No other related proteins were identified in the Arabidopsis genome. Given that mammalian PIG-C and its known homologs in other organisms are relatively divergent in sequence (21.5% identity and 38.4% similarity between HsPIGC and its yeast homolog GPI2), SETH1 likely encodes the Arabidopsis homolog of PIG-C. PIG-C and GPI2 are associated with the endoplasmic reticulum and show multiple conserved hydrophobic segments, suggesting that they are integral membrane proteins (Inoue et al., 1996 ). Using topology prediction programs, we identified six to eight potential transmembrane segments in HsPIGC and SETH1, six of which were conserved using the TmHMM_v2 algorithm (http://www.cbs.dtu.dk/services/TMHMM-2.0/).
Disruption of the GPI-GnT Catalytic Subunit PIG-A Has a Male Gametophyte–Specific Effect To further investigate the role of GPI anchor biosynthesis in pollen, we identified a T-DNA insertion, seth2, in At3g45100 that encodes a putative homolog of the GPI-GnT catalytic subunit PIG-A (Figure 1B). SETH2 also is a single-copy gene in Arabidopsis and encodes a protein that is 47.8% identical (64.4% similar) over 494 amino acids to its human homolog PIG-A (Miyata et al., 1993 ). The seth2 mutation was found to result in a male-specific gametophytic defect similar to those of all three seth1 alleles, showing only residual male transmission of 1.6% (Table 1). The insertion in seth2 likely completely blocks GPI-GnT enzyme activity and GPI anchor biosynthesis. The residual transmission of seth1 and seth2 mutant alleles suggests that the gametophytic synthesis of GPI is essential for pollen function but that a few pollen tubes are able to reach and fertilize ovules in the absence of gametophytically synthesized GPIs.
GPI-Deficient Pollen Grains Develop Normally
seth1 and seth2 Mutations Affect Pollen Germination and Tube Growth We tested the pollen germination efficiency of seth1 and seth2 mutants using in vitro germination assays (Figures 2D to 2G). Pollen from wild-type control plants showed germination efficiencies that ranged from 64 to 76%. By contrast, only 31 to 52.6% of pollen from heterozygous mutants was capable of germination (Figure 2H), suggesting that mutant pollen is partially defective for germination in vitro. seth1-3 allowed tetrad analysis of pollen germination ability in vitro. Tetrads containing one to four germinated pollen grains were scored (Figures 3A to 3D). In wild-type control plants (qrt1/qrt1;+/+), 32.5% of tetrads produced three tubes and 29.5% of tetrads produced four tubes (Figure 3E), whereas in qrt1/qrt1;+/seth1-3 plants, only 7.5% of tetrads had three tubes and very few tetrads produced four tubes (0.3%). These data confirm the primary outcome of defective gametophytic GPI synthesis to be reduced pollen germination efficiency in vitro.
To determine if GPI deficiency has an effect on pollen tube elongation, we measured the lengths of pollen tubes from tetrads producing three pollen tubes, reasoning that at least one tube produced by +/seth1-3 tetrads must carry a mutant seth1-3 allele (Figure 3F). The mean pollen tube length was 258 µm in the wild type and 185 µm in +/seth1-3 tetrads, representing a 28% reduction in mean tube length in +/seth1-3. When the frequency distribution of tube lengths was plotted, 28% of +/seth1-3 tetrads produced pollen tubes of <100 µm, whereas wild-type tetrads showed only 8% of tubes of <100 µm. These data demonstrate a further role for GPI-GnT components in pollen tube elongation in vitro. To investigate potential cell wall composition defects associated with in vitro germination and growth failures, we stained wild-type and mutant pollen with calcofluor white, ruthenium red, and aniline blue to detect cellulose, pectin, and callose, respectively. No abnormalities were detected in cellulose or pectin staining. By contrast, intense patches of callose staining (Figure 3H) were observed in nongerminated pollen from seth1-3 heterozygotes. In the wild type, only 4.5% of ungerminated pollen grains showed abnormal callose deposition, whereas 13.5% of pollen from seth1-3 heterozygotes showed very strong callose staining (n = 400). Tetrads producing three tubes (where at least one is known to carry a mutant allele) were examined further. In 85% (n = 40) of tetrads from seth1-3 heterozygotes producing three pollen tubes, one tube showed high levels of abnormal callose deposition, with irregular banding patterns transverse to the pollen tube axis (Figure 3J). Mutant pollen tube tips also showed abnormal callose staining (Figure 3L). Similar phenotypes were observed in seth1-2 and seth2 mutants but not in pollen tubes from wild-type tetrads that produced three tubes (n = 60). Reduced germination and tube growth efficiency in seth2 were confirmed using in vivo pollination assays (Figure 4). To avoid the potentially complicating effects of stigma maturity and emasculation stresses, pollination was performed on stigmas of male-sterile plants (ms1-1/ms1-1). Pistils of ms1-1 plants were confirmed to respond similarly to those of the wild type or seth2 heterozygotes in competitive pollinations, such that seth2 transmission on ms1-1 pistils was 1.7% (n = 120).
We developed an in vivo pollination assay to initially measure the overall efficiency of pollen germination and tube growth in vivo. This involved pollinating excised pistils harvested from male-sterile (ms1-1) plants and subsequently treating pistils with Alexander stain (Alexander, 1969 ). This process allowed pollen germination and tube growth to be scored based on the presence or density of the cytoplasm (Figures 4A and 4B). In the wild type, only 8% of pollen grains attached to the papillar cells were strongly stained at 4 h after pollination, showing that most had transferred their cytoplasm into the pollen tube. By contrast, 51 and 53% of pollen grains from seth1-2 and seth2 heterozygotes, respectively, were strongly stained after the same period (Figure 4C). This resulted from a complete failure to germinate or failure to establish sufficiently long pollen tubes to ensure complete translocation of the cytoplasm out of the pollen grains. Pollen germination and tube growth also were assayed at 2 h after pollination by staining fixed pistils with aniline blue (Figures 4D and 4E). On ms1-1 stigmas pollinated with wild-type pollen, 97.4% of pollen grains had developed a pollen tube and 1% had initiated germination, indicated by the local outgrowth of the pollen wall and/or the polarized deposition of callose (Figure 4D). By contrast, in pollinations with pollen from seth1-2 heterozygotes, only 55% of pollen grains developed a pollen tube, 27% had initiated germination, and 18% showed no evidence of polarized growth (Figure 4E). A slightly greater germination efficiency (64%) was observed with pollen from seth2 heterozygotes, but 36% failed to germinate (Figure 4E). We conclude that GPI biosynthetic mutations disturb pollen germination and tube growth in planta but that a proportion of GPI-deficient pollen grains are able to support the development of a pollen tube on stigmatic papillae.
Limited Pollination Does Not Restore Male Transmission in GPI-Deficient Mutants
SETH1 and SETH2 Are Expressed Widely in Sporophytic and Gametophytic Tissues
Identification of Pollen-Expressed Genes Encoding GAPs
RT-PCR analysis of pollen and sporophytic tissues (root, stem, leaf, and flower) revealed that 15 of these 41 GAP mRNAs were detected specifically in flowers and pollen (Table 2). These tissue-specific transcripts encode a functionally divergent set of proteins: Bcp1-like, AG peptides, classic arabinogalactan proteins, fasciclin-like AGPs (FLAs), -1,3-glucanases, aspartylproteases, glycerophosphodiesterase-like proteins, lipid transfer–like proteins, COBRA-like proteins, and unknown GAPs.
GAPs in Pollen
RT-PCR analysis (Table 2) confirmed that all of the 11 corresponding genes were expressed in pollen, 7 of them in a tissue-specific manner. At5g64790, At3g18590, At1g48940, and At2g24450 were expressed preferentially in pollen, whereas the expression of At1g64760, At1g18280, and At1g54860 was restricted to pollen and certain sporophytic tissues.
GPI modification of proteins occurs in most eukaryotic systems and appears to be essential for the modulation of cell surface properties. In plants, GAPs fulfill a number of potential functions, although the significance of GPI anchoring and the biological roles of GAPs remain poorly understood. We identified and characterized four insertional mutations that disrupt two probable subunits of the GPI-GnT complex, PIG-C (seth1) and PIG-A (seth2). Heterozygous GPI-GnT complex mutations in Arabidopsis have no effect on sporophytic development and megagametogenesis but show gametophytic, male-specific defects in fertility. Mutant pollen is viable, but the majority of GPI-deficient pollen grains fail during either germination or early tube growth. Our results suggest that GPI anchoring is required during both phases of post-pollination development.
Recent studies in mice also have demonstrated a reproductive role for GPI anchoring, but in female fertility. Conditional PIG-A knockout female mice are infertile, and eggs recovered after mating remain unfertilized, suggesting that GAPs on the egg surface play a role in gamete fusion (Alfieri et al., 2003 Although highly penetrant, GPI-GnT complex mutations occasionally were transmitted through pollen. Therefore, a low percentage of mutant pollen grains were able to germinate and develop functional pollen tubes. In vivo germination assays indicated that 26% of pollen grains carrying the seth2 mutant allele were able to germinate, but genetic analysis revealed only 1.6% male transmission, suggesting that GPIs also are required during pollen germination and pollen tube elongation. Indeed, GPI-deficient pollen tubes grown in vitro were shorter that their wild-type counterparts, and most showed high levels of abnormal callose deposition. In vivo analysis showed that only 9.2% of seth2 pollen grains (4.6% of the total population) were able to develop sufficiently long pollen tubes to allow cytoplasmic translocation. Together, these data suggest that 74% of seth2 pollen fail to germinate and another 16.8% develop only short pollen tubes.
The residual transmission of GPI-deficient mutations might be explained by the existence of a pool of GAPs, GPIs, or GPI precursors associated with the endoplasmic reticulum and inherited through meiosis. Saccharomyces cerevisiae GPI-deficient haploid ascospores are able to germinate and complete up to four cell divisions (Leidich et al., 1995
The total number of Arabidopsis proteins predicted to be attached to the cell surface by GPI anchoring is 248 (Borner et al., 2002
GAPs are targeted to the cell surface in a polarized manner in many organisms. There is increasing evidence that many GAPs in animal and yeast cells can be clustered into sphingolipid- and sterol-enriched membrane microdomains, known as lipid rafts (reviewed by Muniz and Riezman, 2000
It may be significant that all four Arabidopsis GAPs characterized to date have roles in directional growth or cell expansion and/or influence the properties of the cell wall. COBRA is required for polarized longitudinal expansion in the root, which Schindelman et al. (2001)
GPI deficiency might differentially affect the fate of GAP precursors, but it is likely to prevent their correct targeting to the plasma membrane. For example, in GPI-deficient mutants generated by the heterologous expression of Trypanosoma brucei GPI-PLC, of four proteins that normally are GPI anchored in Trypanosoma cruzi, two were secreted prematurely and the other two were degraded intracellularly (Garg et al., 1997
Moreover, the potential importance of free GPIs should not be neglected. Although we are unaware of any evidence from plants, free GPIs are present at the surfaces of mammalian (Singh et al., 1996 The diversity of GAPs expressed in pollen highlights the complexity of the mechanisms underlying post-pollination events. Pollen GAP protein homologies suggest functions associated with the regulation of the structural properties and synthesis of the pollen tube wall and signaling at the pollen tube surface. GPI-deficient pollen, which is viable until germination, represents a valuable in vivo system that allows the stepwise dissection of GPI biosynthesis and the functional analysis of GPI-anchored cell surface proteins in plants.
Mutant Lines and Growth Conditions DsE and DsG lines in the Landsberg erecta ecotype were generated by U. Grossniklaus and co-workers at Cold Spring Harbor Laboratory (Cold Spring Harbor, NY) as described (Sundaresan et al., 1995 ; Moore et al., 1997). seth1-1 was isolated from a genetic screen of 3616 Ds lines based on segregation ratio distortion (E. Lalanne et al., unpublished data). Thermal asymmetric interlaced PCR was performed according to Liu et al. (1995) with minor modifications. Ds-flanking sequences were amplified using three GUS-specific nested primers (GUS-1, 5'-CGTAATGAGTGACCGCATCG-3'; GUS-2, 5'-GACGTTGCCCGCATAATTAC-3'; GUS-3, 5'-GATCCAGACTGAATGCCCAC-3') combined with the AD1, AD2, or AD3 degenerate primers (Liu et al., 1995). The Ds-flanking DNA junction was confirmed using Ds5-1 (Grossniklaus et al., 1998) and a gene-specific primer (5'-ATCATGCAAGAAGAGATGAAG-3'). seth1-2 (Garlic_674B03) and seth1-3 (Garlic_165E01) were obtained from Syngenta. seth2 (SALK_039500) was generated by the Salk Institute. Insertion mutant information was obtained from the SIGnAL World Wide Web site at http://signal.salk.edu.
seth1-1 and seth2 seeds were sterilized in a drop of 95% ethanol. Ethanol was allowed to evaporate overnight. Sterilized seeds were plated onto kanamycin (50 ng/L)–supplemented medium (0.5x Murashige and Skoog [1962]
Genetic Transmission through Male and Female Gametes
Cytological and Phenotypic Analyses of Pollen
In vitro germination assays were performed as follows. Individual open flowers were collected in microtiter plates (TC microwell 96F; Nucleon Biosciences, Glasgow, Scotland) containing 50 µL of germination medium (Derksen et al., 2002 To determine in vivo germination efficiency, excised ms1-1 stigmas were cut at the base and inserted vertically into solid agar (1% in water) in a 9-cm Petri dish. Limited pollinations were performed as described above. Stigmas were transferred on a microscope slide and stained with aniline blue solution at 2 h after pollination or with Alexander staining at 4 h after pollination. More than 400 pollen grains deposited on 20 stigmas were analyzed per line.
RNA Extraction and Affymetrix Complete Genome Microarray Hybridization
Biochemical Fractionation and Preparation of GPI-Anchored Proteins
Electrophoretic Analysis and Mass Spectrometry Upon request, materials integral to the findings presented in this publication will be made available in a timely manner to all investigators on similar terms for noncommercial research purposes. To obtain materials, please contact David Twell, twe{at}le.ac.uk.
We thank the Salk Institute Genomic Analysis Laboratory for providing sequence-indexed Arabidopsis T-DNA insertion mutants. We thank the Torrey Mesa Research Institute (Syngenta) for providing insertion lines from the SAIL collection, and James Moore, Wendy Gagliano, and Jean-Phillippe Vielle Calzada for help in generating Ds insertion lines. Seeds of ms1-1 and SALK T-DNA mutants were provided by the Nottingham Arabidopsis Stock Centre. Funding for the SIGnAL indexed insertion mutant collection was provided by the National Science Foundation. This work was made possible by research grants from the Biotechnology and Biological Sciences Research Council (BBSRC), the BBSRC Investigating Gene Function Initiative, and services provided through the GARNet transcriptomic and proteomic facilities. D.H. was supported through a Royal Society/North Atlantic Treaty Organization fellowship and Academy of Sciences of the Czech Republic Grant IAA5038207. G.H.H.B. received a BBSRC research studentship and a scholarship from the Studienstiftung des Deutschen Volkes. U.G. was supported by the Cold Spring Harbor Laboratory President's Council, the European Molecular Biology Organization, the Human Frontier Science Program, and the Kanton of Zürich.
Online version contains Web-only data.  Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.014407.
1 To whom correspondence should be addressed. E-mail twe{at}le.ac.uk; fax 44-116-2522791. Received June 5, 2003; accepted October 23, 2003.
Alexander, M.P. (1969). Differential staining of aborted and nonaborted pollen. Stain Technol. 44, 117–122.[ISI][Medline]
Alfieri, J.A., Martin, A.D., Takeda, J., Kondoh, G., Myles, D.G., and Primakoff, P. (2003). Infertility in female mice with an oocyte-specific knockout of GPI-anchored proteins. J. Cell Sci. 116, 2149–2155.
Bagnat, M., and Simons, K. (2002). Cell surface polarization during yeast mating. Proc. Natl. Acad. Sci. USA 99, 14183–14188.
Benachour, A., Sipos, G., Flury, I., Reggiori, F., Canivenc-Gansel, E., Vionnet, C., Conzelmann, A., and Benghezal, M. (1999). Deletion of GPI7, a yeast gene required for addition of a side chain to the glycosylphosphatidylinositol (GPI) core structure, affects GPI protein transport, remodeling, and cell wall integrity. J. Biol. Chem. 274, 15251–15261. Bessler, M., Rosti, V., Peng, Y., Cattoretti, G., Notaro, R., Ohsako, S., Elkon, K.B., and Luzzatto, L. (2002). Glycosylphosphatidylinositol-linked proteins are required for maintenance of a normal peripheral lymphoid compartment but not for lymphocyte development. Eur. J. Immunol. 32, 2607–2616.[CrossRef][Medline]
Borner, G.H.H., Lilley, K.S., Stevens, T.J., and Dupree, P. (2003). Identification of glycosylphosphatidylinositol-anchored proteins in Arabidopsis: A proteomic and genomic analysis. Plant Physiol. 132, 568–577.
Borner, G.H.H., Sherrier, D.J., Stevens, T.J., Arkin, I.T., and Dupree, P. (2002). Prediction of glycosylphosphatidylinositol-anchored proteins in Arabidopsis: A genomic analysis. Plant Physiol. 129, 486–499. Derksen, J., Knuiman, B., Hoedemaekers, K., Guyon, A., Bonhomme, S., and Pierson, E.S. (2002). Growth and cellular organization of Arabidopsis pollen tubes in vitro. Sex. Plant Reprod. 15, 133–139.[CrossRef]
Doblin, M.S., De Melis, L., Newbigin, E., Bacic, A., and Read, S.M. (2001). Pollen tubes of Nicotiana alata express two genes from different Fivaz, M., Vilbois, F., Thurnheer, S., Pasquali, C., Abrami, L., Bickel, P.E., Parton, R.G., and van der Goot, F.G. (2002). Differential sorting and fate of endocytosed GPI-anchored proteins. EMBO J. 21, 3989–4000.[CrossRef][ISI][Medline]
Garg, N., Tarleton, R.L., and Mensa-Wilmot, K. (1997). Proteins with glycosylphosphatidylinositol (GPI) signal sequences have divergent fates during a GPI deficiency: GPIs are essential for nuclear division in Trypanosoma cruzi. J. Biol. Chem. 272, 12482–12491.
Gaynor, E.C., Mondesert, G., Grimme, S.J., Reed, S.I., Orlean, P., and Emr, S.D. (1999). MCD4 encodes a conserved endoplasmic reticulum membrane protein essential for glycosylphosphatidylinositol anchor synthesis in yeast. Mol. Biol. Cell 10, 627–648.
Grossniklaus, U., Vielle-Calzada, J.-P., Hoeppner, M.A., and Gagliano, W.B. (1998). Maternal control of embryogenesis by MEDEA, a Polycomb-group gene in Arabidopsis. Science 280, 446–450.
Hilley, J.D., Zawadzki, J.L., McConville, M.J., Coombs, G.H., and Mottram, J.C. (2000). Leishmania mexicana mutants lacking glycosylphosphatidylinositol (GPI):protein transamidase provide insights into the biosynthesis and functions of GPI-anchored proteins. Mol. Biol. Cell 11, 1183–1195.
Hong, Y., Maeda, Y., Watanabe, R., Ohishi, K., Mishkind, M., Riezman, H., and Kinoshita, T. (1999). Pig-n, a mammalian homologue of yeast Mcd4p, is involved in transferring phosphoethanolamine to the first mannose of the glycosylphosphatidylinositol. J. Biol. Chem. 274, 35099–35106.
Honys, D., and Twell, D. (2003). Comparative analysis of the Arabidopsis pollen transcriptome. Plant Physiol. 132, 640–652. Horvath, A., Sütterlin, C., Manning-Krieg, U., Movva, N.R., and Riezman, H. (1994). Ceramide synthesis enhances transport of GPI-anchored proteins to the Golgi apparatus in yeast. EMBO J. 13, 3687–3695.[ISI][Medline]
Howden, R., Park, S.K., Moore, J.M., Orme, J., Grossniklaus, U., and Twell, D. (1998). Selection of T-DNA-tagged male and female gametophytic mutants by segregation distortion in Arabidopsis. Genetics 149, 621–631. Ikezawa, H. (2002). Glycosylphosphatidylinositol (GPI)-anchored proteins. Biol. Pharm. Bull. 25, 409–417.[CrossRef][ISI][Medline] Ikonen, E. (2001). Roles of lipid rafts in membrane transport. Curr. Opin. Cell Biol. 13, 470–477.[CrossRef][ISI][Medline] Ilgoutz, S.C., Zawadzki, J.L., Ralton, J.E., and McConville, M.J. (1999). Evidence that free GPI glycolipids are essential for growth of Leishmania mexicana. EMBO J. 18, 2746–2755.[CrossRef][ISI][Medline] Imbach, T., et al. (2000). Deficiency of dolichol-phosphate-mannose synthase-1 causes congenital disorder of glycosylation type Ie. J. Clin. Invest. 105, 233–239.[ISI][Medline] Inoue, N., Watanabe, R., Takeda, J., and Kinoshita, T. (1996). PIG-C, one of the three human genes involved in the first step of glycosylphosphatidylinositol biosynthesis, is a homologue of Saccharomyces cerevisiae GPI2. Biochem. Biophys. Res. Commun. 226, 193–199.[CrossRef][ISI][Medline]
Johnson, S.A., and McCormick, S. (2001). Pollen germinates precociously in the anthers of raring-to-go, an Arabidopsis gametophytic mutant. Plant Physiol. 126, 685–695.
Leidich, S.D., Kostova, Z., Latek, R.R., Costello, L.C., Drapp, D.A., Gray, W., Fassler, J.S., and Orlean, P. (1995). Temperature-sensitive yeast GPI anchoring mutants gpi2 and gpi3 are defective in the synthesis of N-acetylglucosaminyl phosphatidylinositol: Cloning of the GPI2 gene. J. Biol. Chem. 270, 13029–13035. Liu, Y.G., Mitsukawa, N., Oosumi, T., and Whittier, R.F. (1995). Efficient isolation and mapping of Arabidopsis thaliana T-DNA insert junctions by thermal asymmetric interlaced PCR. Plant J. 8, 457–463.[CrossRef][ISI][Medline] Meyer, U., Benghezal, M., Imhof, I., and Conzelmann, A. (2000). Active site determination of Gpi8p, a caspase-related enzyme required for glycosylphosphatidylinositol anchor addition to proteins. Biochemistry 39, 3461–3471.[CrossRef][Medline]
Miyata, T., Takeda, J., Iida, Y., Yamada, N., Inoue, N., Takahashi, M., Maeda, K., Kitani, T., and Kinoshita, T. (1993). The cloning of PIG-A, a component in the early step of GPI-anchor biosynthesis. Science 259, 1318–1320.
Moore, J.M., Vielle Calzada, J.-P., Gagliano, W., and Grossniklaus, U. (1997). Genetic characterization of hadad, a mutant disrupting megagametogenesis in Arabidopsis thaliana. Cold Spring Harbor Symp. Quant. Biol. 62, 35–47. Muniz, M., and Riezman, H. (2000). Related intracellular transport of GPI-anchored proteins. EMBO J. 19, 10–15.[CrossRef][ISI][Medline] Murashige, T., and Skoog, F. (1962). A revised medium for rapid growth and bioassays with tobacco tissue culture. Physiol. Plant. 15, 473–497.[CrossRef] Nichols, B.J. (2002). A distinct class of endosome mediates clathrin-independent endocytosis to the Golgi complex. Nat. Cell Biol. 5, 374–378.
Oxley, D., and Bacic, A. (1999). Structure of the glycosylphosphatidylinositol anchor of an arabinogalactan protein from Pyrus communis suspension-cultured cells. Proc. Natl. Acad. Sci. USA 96, 14246–14251. Park, S.K., Howden, R., and Twell, D. (1998). The Arabidopsis thaliana gametophytic mutation gemini pollen 1 disrupts microspore polarity, division asymmetry and pollen cell fate. Development 125, 3789–3799.[Abstract]
Park, S.K., and Twell, D. (2001). Novel patterns of ectopic cell plate growth and lipid body distribution in the Arabidopsis gemini pollen1 mutant. Plant Physiol. 126, 899–909. Peskan, T., Westermann, M., and Oelmuller, R. (2000). Identification of low-density Triton X-100-insoluble plasma membrane microdomains in higher plants. Eur. J. Biochem. 267, 6989–6995.[ISI][Medline] Premkumar, D.R., Fukuoka, Y., Sevlever, D., Brunschwig, E., Rosenberry, T.L., Tykocinski, M.L., and Medof, M.E. (2001). Properties of exogenously added GPI-anchored proteins following their incorporation into cells. J. Cell. Biochem. 82, 234–245.[CrossRef][ISI][Medline]
Preuss, D., Rhee, S.Y., and Davis, R.W. (1994). Tetrad analysis possible in Arabidopsis with mutation of the QUARTET (QRT) genes. Science 264, 1458–1460.
Rodriguez-Peña, J.M., Rodriguez, C., Alvarez, A., Nombela, C., and Arroyo, J. (2002). Mechanisms for targeting of the Saccharomyces cerevisiae GPI-anchored cell wall protein Crh2p to polarised growth sites. J. Cell Sci. 115, 2549–2558.
Rosti, V. (2000). The molecular basis of paroxysmal nocturnal hemoglobinuria. Haematologica 85, 82–87.
Roudier, F., Schindelman, G., DeSalle, R., and Benfey, P.N. (2002). The COBRA family of putative GPI-anchored proteins in Arabidopsis: A new fellowship in expansion. Plant Physiol. 130, 538–548. Sabharanjak, S., Sharma, P., Parton, R.G., and Mayor, S. (2002). GPI-anchored proteins are delivered to recycling endosomes via a distinct cdc42-regulated, clathrin-independent pinocytic pathway. Dev. Cell 4, 411–423.
Schindelman, G., Morikami, A., Jung, J., Baskin, T.I., Carpita, N.C., Derbyshire, P., McCann, M.C., and Benfey, P.N. (2001). COBRA encodes a putative GPI-anchored protein, which is polarly localized and necessary for oriented cell expansion in Arabidopsis. Genes Dev. 15, 1115–1127.
Schultz, C.J., Johnson, K.L., Currie, G., and Bacic, A. (2000). The classical arabinogalactan protein gene family of Arabidopsis. Plant Cell 12, 1751–1768.
Sedbrook, J.C., Carroll, K.L., Hung, K.F., Masson, P.H., and Somerville, C.R. (2002). The Arabidopsis SKU5 gene encodes an extracellular glycosyl phosphatidylinositol–anchored glycoprotein involved in directional root growth. Plant Cell 14, 1635–1648.
Sessions, A., et al. (2002). A high-throughput Arabidopsis reverse genetics system. Plant Cell 14, 2985–2994. Sherrier, D.J., Prime, T.A., and Dupree, P. (1999). Glycosylphosphatidylinositol-anchored cell-surface proteins from Arabidopsis. Electrophoresis 20, 2027–2035.[CrossRef][ISI][Medline]
Shi, H., Kim, Y., Guo, Y., Stevenson, B., and Zhu, J.K. (2003). The Arabidopsis SOS5 locus encodes a putative cell surface adhesion protein and is required for normal cell expansion. Plant Cell 15, 19–32.
Singh, N., Liang, L.N., Tykocinski, M.L., and Tartakoff, A.M. (1996). A novel class of cell surface glycolipids of mammalian cells: Free glycosyl phosphatidylinositols. J. Biol. Chem. 271, 12879–12884.
Sundaresan, V., Springer, P., Volpe, T., Haward, S., Jones, J.D., Dean, C., Ma, H., and Martienssen, R. (1995). Patterns of gene action in plant development revealed by enhancer trap and gene trap transposable elements. Genes Dev. 9, 1797–1810. Takos, A.M., Dry, I.B., and Soole, K.L. (1997). Detection of glycosyl-phosphatidylinositol-anchored proteins on the surface of Nicotiana tabacum protoplasts. FEBS Lett. 405, 1–4.[CrossRef][ISI][Medline] Tsui-Pierchala, B.A., Encinas, M., Milbrandt, J., and Johnson, E.M. (2002). Lipid rafts in neuronal signaling and function. Trends Neurosci. 25, 412–417.[CrossRef][ISI][Medline] Udenfriend, S., and Kodukula, K. (1995). How glycosylphosphatidylinositol-anchored membrane proteins are made. Annu. Rev. Biochem. 64, 563–591.[ISI][Medline]
Willemsen, V., Friml, J., Grebe, M., Van Den Toorn, A., Palme, K., and Scheres, B. (2003). Cell polarity and PIN protein positioning in Arabidopsis require STEROL METHYLTRANSFERASE1 function. Plant Cell 15, 612–625. |
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ABSTRACT
INTRODUCTION
site of candidate proteins involves the GAA1 and GPI8 proteins. In the Golgi apparatus, the GPI core structure in animals and yeast is elaborated further by the addition of sugar side chains on mannose residues and often by remodeling of the lipid to a ceramide. Although GPI anchor biosynthesis has not been studied in plants, Oxley and Bacic (1999)
