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David Twell

Publications and source records attributed to David Twell.

At least 19 recordsLinked to original sources
PubMed2006

Identification of microspore-active promoters that allow targeted manipulation of gene expression at early stages of microgametogenesis in Arabidopsis.

BACKGROUND: The effective functional analysis of male gametophyte development requires new tools enabling the spatially and temporally controlled expression of both marker genes and modified genes of interest. In particular, promoters driving expression at earlier developmental stages including microspores are required. RESULTS: Transcriptomic datasets covering four progressive stages of male gametophyte development in Arabidopsis were used to select candidate genes showing early expression profiles that were male gametophyte-specific. Promoter-GUS reporter analysis of candidate genes identified three promoters (MSP1, MSP2, and MSP3) that are active in microspores and are otherwise specific to the male gametophyte and tapetum. The MSP1 and MSP2 promoters were used to successfully complement and restore the male transmission of the gametophytic two-in-one (tio) mutant that is cytokinesis-defective at first microspore division. CONCLUSION: We demonstrate the effective application of MSP promoters as tools that can be used to elucidate gametophytic gene functions in microspores in a male-specific manner.

Arabidopsis↗
PubMed2006

Generalization of DNA microarray dispersion properties: microarray equivalent of t-distribution.

BACKGROUND: DNA microarrays are a powerful technology that can provide a wealth of gene expression data for disease studies, drug development, and a wide scope of other investigations. Because of the large volume and inherent variability of DNA microarray data, many new statistical methods have been developed for evaluating the significance of the observed differences in gene expression. However, until now little attention has been given to the characterization of dispersion of DNA microarray data. RESULTS: Here we examine the expression data obtained from 682 Affymetrix GeneChips with 22 different types and we demonstrate that the Gaussian (normal) frequency distribution is characteristic for the variability of gene expression values. However, typically 5 to 15% of the samples deviate from normality. Furthermore, it is shown that the frequency distributions of the difference of expression in subsets of ordered, consecutive pairs of genes (consecutive samples) in pair-wise comparisons of replicate experiments are also normal. We describe a consecutive sampling method, which is employed to calculate the characteristic function approximating standard deviation and show that the standard deviation derived from the consecutive samples is equivalent to the standard deviation obtained from individual genes. Finally, we determine the boundaries of probability intervals and demonstrate that the coefficients defining the intervals are independent of sample characteristics, variability of data, laboratory conditions and type of chips. These coefficients are very closely correlated with Student's t-distribution. CONCLUSION: In this study we ascertained that the non-systematic variations possess Gaussian distribution, determined the probability intervals and demonstrated that the K(alpha) coefficients defining these intervals are invariant; these coefficients offer a convenient universal measure of dispersion of data. The fact that the K(alpha) distributions are so close to t-distribution and independent of conditions and type of arrays suggests that the quantitative data provided by Affymetrix technology give "true" representation of physical processes, involved in measurement of RNA abundance. REVIEWERS: This article was reviewed by Yoav Gilad (nominated by Doron Lancet), Sach Mukherjee (nominated by Sandrine Dudoit) and Amir Niknejad and Shmuel Friedland (nominated by Neil Smalheiser).

Journal Article↗
PubMed2006

Integrating membrane transport with male gametophyte development and function through transcriptomics.

Male fertility depends on the proper development of the male gametophyte, successful pollen germination, tube growth, and delivery of the sperm cells to the ovule. Previous studies have shown that nutrients like boron, and ion gradients or currents of Ca2+, H+, and K+ are critical for pollen tube growth. However, the molecular identities of transporters mediating these fluxes are mostly unknown. As a first step to integrate transport with pollen development and function, a genome-wide analysis of transporter genes expressed in the male gametophyte at four developmental stages was conducted. Approximately 1,269 genes encoding classified transporters were collected from the Arabidopsis (Arabidopsis thaliana) genome. Of 757 transporter genes expressed in pollen, 16% or 124 genes, including AHA6, CNGC18, TIP1.3, and CHX08, are specifically or preferentially expressed relative to sporophytic tissues. Some genes are highly expressed in microspores and bicellular pollen (COPT3, STP2, OPT9), while others are activated only in tricellular or mature pollen (STP11, LHT7). Analyses of entire gene families showed that a subset of genes, including those expressed in sporophytic tissues, was developmentally regulated during pollen maturation. Early and late expression patterns revealed by transcriptome analysis are supported by promoter::beta-glucuronidase analyses of CHX genes and by other methods. Recent genetic studies based on a few transporters, including plasma membrane H+ pump AHA3, Ca2+ pump ACA9, and K+ channel SPIK, further support the expression patterns and the inferred functions revealed by our analyses. Thus, revealing the distinct expression patterns of specific transporters and unknown polytopic proteins during microgametogenesis provides new insights for strategic mutant analyses necessary to integrate the roles of transporters and potential receptors with male gametophyte development.

Arabidopsis↗
PubMed2005

A divergent cellular role for the FUSED kinase family in the plant-specific cytokinetic phragmoplast.

The FUSED (FU) Ser/Thr protein kinase family has a key role in the hedgehog signaling pathway known to control cell proliferation and patterning in fruit flies and humans . The genomes of Arabidopsis thaliana and rice each encode a single Fu ortholog, but their role is unknown. Here, we show that cytokinesis-defective mutants, which we named two-in-one (tio), result from mutations in Arabidopsis Fu. Phenotypic analysis of tio mutants reveals an essential role for TIO in conventional modes of cytokinesis in plant meristems and during male gametogenesis. TIO also has a key role in nonconventional modes of cytokinesis (cellularization) during female gametogenesis. We demonstrate that TIO is tightly localized to the midline of the nascent phragmoplast and remains associated with the expanding phragmoplast ring. These data reveal the evolution of a divergent role for the Fu kinase family as an essential phragmoplast-associated protein that functions in different cell type-specific modes of cytokinesis in plants.

Arabidopsis↗
PubMed2005

A molecular-genetic study of the Arabidopsis Toc75 gene family.

Toc75 (translocon at the outer envelope membrane of chloroplasts, 75 kD) is the protein translocation channel at the outer envelope membrane of plastids and was first identified in pea (Pisum sativum) using biochemical approaches. The Arabidopsis (Arabidopsis thaliana) genome contains three Toc75-related sequences, termed atTOC75-I, atTOC75-III, and atTOC75-IV, which we studied using a range of molecular, genetic, and biochemical techniques. Expression of atTOC75-III is strongly regulated and at its highest level in young, rapidly expanding tissues. By contrast, atTOC75-IV is expressed uniformly throughout development and at a much lower level than atTOC75-III. The third sequence, atTOC75-I, is a pseudogene that is not expressed due to a gypsy/Ty3 transposon insertion in exon 1, and numerous nonsense, frame-shift, and splice-junction mutations. The expressed genes, atTOC75-III and atTOC75-IV, both encode integral envelope membrane proteins. Unlike atToc75-III, the smaller atToc75-IV protein is not processed upon targeting to the envelope, and its insertion does not require ATP at high concentrations. The atTOC75-III gene is essential for viability, since homozygous atToc75-III knockout mutants (termed toc75-III) could not be identified, and aborted seeds were observed at a frequency of approximately 25% in the siliques of self-pollinated toc75-III heterozygotes. Homozygous toc75-III embryos were found to abort at the two-cell stage. Homozygous atToc75-IV knockout plants (termed toc75-IV) displayed no obvious visible phenotypes. However, structural abnormalities were observed in the etioplasts of toc75-IV seedlings and atTOC75-IV overexpressing lines, and toc75-IV plants were less efficient at deetiolation than wild type. These results suggest some role for atToc75-IV during growth in the dark.

Amino Acid Sequence↗
PubMed2005

A novel class of MYB factors controls sperm-cell formation in plants.

In contrast to animals, the plant male germline is established after meiosis in distinctive haploid structures, termed pollen grains. The germline arises by a distinct asymmetric division of the meiotic products . The fates of the resulting vegetative and generative cells are distinct. In contrast to the larger vegetative cell, arrested in the G1 phase of the cell cycle, the smaller generative cell divides once to produce the two male gametes or sperm cells. Sperm cells are delivered to the female gametes by the pollen tube, which develops from the vegetative cell. In spite of recent efforts to understand pollen development , the molecular pathway controlling sperm-cell ontogenesis is unknown. Here, we present the isolation of DUO1, a novel R2R3 MYB gene of Arabidopsis, as the first gene shown to control male gamete formation in plants. DUO1 is specifically expressed in the male germline, and DUO1 protein accumulates in sperm-cell nuclei. Mutations in DUO1 produce a single larger diploid sperm cell unable to perform fertilization. DUO1 appears to be evolutionarily conserved in several plant species and defines a new subfamily of pollen-specific MYB genes.

Amino Acid Sequence↗
PubMed2005

Translation initiation factors eIF4E and eIFiso4E are required for polysome formation and regulate plant growth in tobacco.

Eukaryotic initiation factor eIF4E plays a pivotal role in translation initiation. As a component of the ternary eIF4F complex, eIF4E interacts with the mRNA cap structure to facilitate recruitment of the 40S ribosomal subunit onto mRNA. Plants contain two distinct cap-binding proteins, eIF4E and eIFiso4E, that assemble into different eIF4F complexes. To study the functional roles of eIF4E and eIFiso4E in tobacco, we isolated two corresponding cDNAs, NteIF4E1 and NteIFiso4E1, and used these to deplete cap-binding protein levels in planta by antisense downregulation. Antibodies raised against recombinant NteIF4E1 detected three distinct cap-binding proteins in tobacco leaf extracts; NteIF4E and two isoforms of NteIFiso4E. The three cap-binding proteins were immuno-detected in all tissues analysed and were coordinately regulated, with peak expression in anthers and pollen. Transgenic tobacco plants showing significant depletion of either NteIF4E or the two NteIFiso4E isoforms displayed normal vegetative development and were fully fertile. Interestingly, NteIFiso4E depletion resulted in a compensatory increase in NteIF4E levels, whereas the down-regulation of NteIF4E did not trigger a reciprocal increase in NteIFiso4E levels. The antisense depletion of both NteIF4E and NteIFiso4E resulted in plants with a semi-dwarf phenotype and an overall reduction in polyribosome loading, demonstrating that both eIF4E and eIFiso4E support translation initiation in planta, which suggests their potential role in the regulation of plant growth.

Amino Acid Sequence↗
PubMed2005

In vivo studies on the roles of Tic110, Tic40 and Hsp93 during chloroplast protein import.

A multisubunit translocon of the inner envelope membrane, termed Tic, mediates the late stages of protein import into chloroplasts. Membrane proteins, Tic110 and Tic40, and a stromal chaperone, Hsp93, have been proposed to function together within the Tic complex. In Arabidopsis, single genes, atTIC110 and atTIC40, encode the Tic proteins, and two homologous genes, atHSP93-V and atHSP93-III, encode Hsp93. These four genes exhibited relatively uniform patterns of expression, suggesting important roles for plastid biogenesis throughout development and in all tissues. To investigate the roles played by these proteins in vivo, we conducted a comparative study of T-DNA knockout mutants for each Tic gene, and for the most abundantly expressed Hsp93 gene, atHSP93-V. In the homozygous state, the tic110 mutation caused embryo lethality, implying an essential role for atTic110 during plastid biogenesis. Homozygous tic110 embryos exhibited retarded growth, developmental arrest at the globular stage and a 'raspberry-like' embryo-proper phenotype. Heterozygous tic110 plants, and plants homozygous for the tic40 and hsp93-V mutations, exhibited chlorosis, aberrant chloroplast biogenesis, and inefficient chloroplast-import of both photosynthetic and non-photosynthetic preproteins. Non-additive interactions amongst the mutations occurred in double mutants, suggesting that the three components may cooperate during chloroplast protein import.

Arabidopsis↗
PubMed2004

Male germ line development in Arabidopsis. duo pollen mutants reveal gametophytic regulators of generative cell cycle progression.

Male germ line development in flowering plants is initiated with the formation of the generative cell that is the progenitor of the two sperm cells. While structural features of the generative cell are well documented, genetic programs required for generative cell cycle progression are unknown. We describe two novel Arabidopsis (Arabidopsis thaliana) mutants, duo pollen1 (duo1) and duo pollen2 (duo2), in which generative cell division is blocked, resulting in the formation of bicellular pollen grains at anthesis. duo1 and duo2 map to different chromosomes and act gametophytically in a male-specific manner. Both duo mutants progress normally through the first haploid division at pollen mitosis I (PMI) but fail at distinct stages of the generative cell cycle. Mutant generative cells in duo1 pollen fail to enter mitosis at G2-M transition, whereas mutant generative cells in duo2 enter PMII but arrest at prometaphase. In wild-type plants, generative and sperm nuclei enter S phase soon after inception, implying that male gametic cells follow a simple S to M cycle. Mutant generative nuclei in duo1 complete DNA synthesis but bypass PMII and enter an endocycle during pollen maturation. However, mutant generative nuclei in duo2 arrest in prometaphase of PMII with a 2C DNA content. Our results identify two essential gametophytic loci required for progression through different phases of the generative cell cycle, providing the first evidence to our knowledge for genetic regulators of male germ line development in flowering plants.

Arabidopsis↗
PubMed2004

Expression of beta-galactosidase and beta-xylosidase genes during microspore and pollen development.

Tobacco (Nicotiana tabacum L.) microspores at the time of mitosis are characterized by the abundant occurrence of 92- and 98-kDa glycoproteins (GP92 and GP98). GP92 is a soluble protein while GP98 is bound to the insoluble microspore fraction. Both glycoproteins were isolated by affinity chromatography and SDS-PAGE and analysed by MS. Peptide sequences were determined by mu-HPLC/nano-ESI-MS/MS (electrospray ionization tandem MS). GP92 displayed homology to beta-galactosidase (EC 3.2.1.23) and GP98 to beta-xylosidase (EC 3.2.1.37) from Arabidopsis thaliana (L.) Heynh. The activities of the two enzymes in microspore and pollen extracts of tobacco exhibited similar developmental changes to the occurrence of GP92 and GP98, with a maximum around microspore mitosis. These two glycoproteins are the first identified enzymes characteristic of mitotic microspores. Arabidopsis transcriptomic data for five beta-galactosidase and three beta-xylosidase genes abundantly expressed in pollen were verified by reverse transcription-PCR of RNA from different stages of Arabidopsis pollen development and from various parts of the sporophyte. The results showed abundant expression of two genes (At5g20710, At1g31740) homologous to tobacco GP92 in microspores and early pollen, and of three genes (At5g56870, At2g16730 and At4g35010) in maturing pollen. Analysis of beta-xylosidases showed abundant expression of a late pollen-specific gene At3g62710 and low expression of an early gene At5g10560. It is suggested that the early beta-galactosidase and beta-xylosidase genes may participate in cell wall loosening associated with pollen expansion after microspore mitosis and that the products of the late genes may play a role in cell expansion during pollen germination.

Arabidopsis↗
PubMed2004

Transcriptome analysis of haploid male gametophyte development in Arabidopsis.

BACKGROUND: The haploid male gametophyte generation of flowering plants consists of two- or three-celled pollen grains. This functional specialization is thought to be a key factor in the evolutionary success of flowering plants. Moreover, pollen ontogeny is also an attractive model in which to dissect cellular networks that control cell growth, asymmetric cell division and cellular differentiation. Our objective, and an essential step towards the detailed understanding of these processes, was to comprehensively define the male haploid transcriptome throughout development. RESULTS: We have developed staged spore isolation procedures for Arabidopsis and used Affymetrix ATH1 genome arrays to identify a total of 13,977 male gametophyte-expressed mRNAs, 9.7% of which were male-gametophyte-specific. The transition from bicellular to tricellular pollen was accompanied by a decline in the number of diverse mRNA species and an increase in the proportion of male gametophyte-specific transcripts. Expression profiles of regulatory proteins and distinct clusters of coexpressed genes were identified that could correspond to components of gametophytic regulatory networks. Moreover, integration of transcriptome and experimental data revealed the early synthesis of translation factors and their requirement to support pollen tube growth. CONCLUSIONS: The progression from proliferating microspores to terminally differentiated pollen is characterized by large-scale repression of early program genes and the activation of a unique late gene-expression program in maturing pollen. These data provide a quantum increase in knowledge concerning gametophytic transcription and lay the foundations for new genomic-led studies of the regulatory networks and cellular functions that operate to specify male gametophyte development.

Arabidopsis↗
PubMed2004

Expression patterns of a novel AtCHX gene family highlight potential roles in osmotic adjustment and K+ homeostasis in pollen development.

A combined bioinformatic and experimental approach is being used to uncover the functions of a novel family of cation/H(+) exchanger (CHX) genes in plants using Arabidopsis as a model. The predicted protein (85-95 kD) of 28 AtCHX genes after revision consists of an amino-terminal domain with 10 to 12 transmembrane spans (approximately 440 residues) and a hydrophilic domain of approximately 360 residues at the carboxyl end, which is proposed to have regulatory roles. The hydrophobic, but not the hydrophilic, domain of plant CHX is remarkably similar to monovalent cation/proton antiporter-2 (CPA2) proteins, especially yeast (Saccharomyces cerevisiae) KHA1 and Synechocystis NhaS4. Reports of characterized fungal and prokaryotic CPA2 indicate that they have various transport modes, including K(+)/H(+) (KHA1), Na(+)/H(+)-K(+) (GerN) antiport, and ligand-gated ion channel (KefC). The expression pattern of AtCHX genes was determined by reverse transcription PCR, promoter-driven beta-glucuronidase expression in transgenic plants, and Affymetrix ATH1 genome arrays. Results show that 18 genes are specifically or preferentially expressed in the male gametophyte, and six genes are highly expressed in sporophytic tissues. Microarray data revealed that several AtCHX genes were developmentally regulated during microgametogenesis. An exciting idea is that CHX proteins allow osmotic adjustment and K(+) homeostasis as mature pollen desiccates and then rehydrates at germination. The multiplicity of CHX-like genes is conserved in higher plants but is not found in animals. Only 17 genes, OsCHX01 to OsCHX17, were identified in rice (Oryza sativa) subsp. japonica, suggesting diversification of CHX in Arabidopsis. These results reveal a novel CHX gene family in flowering plants with potential functions in pollen development, germination, and tube growth.

Amino Acid Sequence↗
PubMed2004

The putative Arabidopsis homolog of yeast vps52p is required for pollen tube elongation, localizes to Golgi, and might be involved in vesicle trafficking.

The screening of the Versailles collection of Arabidopsis T-DNA transformants allowed us to identify several male gametophytic mutants, including poky pollen tube (pok). The pok mutant, which could only be isolated as a hemizygous line, exhibits very short pollen tubes, explaining the male-specific transmission defect observed in this line. We show that the POK gene is duplicated in the Arabidopsis genome and that the predicted POK protein sequence is highly conserved from lower to higher eukaryotes. The putative POK homolog in yeast (Saccharomyces cerevisiae), referred to as Vps52p/SAC2, has been shown to be located at the late Golgi and to function in a complex with other proteins, Vps53p, Vps54p, and Vps51p. This complex is involved in retrograde trafficking of vesicles between the early endosomal compartment and the trans-Golgi network. We present the expression patterns of the POK gene and its duplicate P2 in Arabidopsis, and of the putative Arabidopsis homologs of VPS53 and VPS54 of yeast. We show that a POK::GFP fusion protein localizes to Golgi in plant cells, supporting the possibility of a conserved function for Vps52p and POK proteins. These results, together with the expression pattern of the POK::GUS fusion and the lack of plants homozygous for the pok mutation, suggest a more general role for POK in polar growth beyond the pollen tube elongation process.

Amino Acid Sequence↗
PubMed2004

Analysis of transposon insertion mutants highlights the diversity of mechanisms underlying male progamic development in Arabidopsis.

To identify genes with essential roles in male gametophytic development, including postpollination (progamic) events, we have undertaken a genetic screen based on segregation ratio distortion of a transposon-borne kanamycin-resistance marker. In a population of 3359 Arabidopsis Ds transposon insertion lines, we identified 20 mutants with stably reduced segregation ratios arising from reduced gametophytic transmission. All 20 mutants showed strict cosegregation of Ds and the reduced gametophytic transmission phenotype. Among these, 10 mutants affected both male and female transmission and 10 mutants showed male-specific transmission defects. Four male and female (ungud) mutants and 1 male-specific mutant showed cellular defects in microspores and/or in developing pollen. The 6 remaining ungud mutants and 9 male-specific (seth) mutants affected pollen functions during progamic development. In vitro and in vivo analyses are reported for 5 seth mutants. seth6 completely blocked pollen germination, while seth7 strongly reduced pollen germination efficiency and tube growth. In contrast, seth8, seth9, or seth10 pollen showed reduced competitive ability that was linked to slower rates of pollen tube growth. Gene sequences disrupted in seth insertions suggest essential functions for putative SETH proteins in diverse processes including protein anchoring, cell wall biosynthesis, signaling, and metabolism.

Arabidopsis↗
PubMed2003

SETH1 and SETH2, two components of the glycosylphosphatidylinositol anchor biosynthetic pathway, are required for pollen germination and tube growth in Arabidopsis.

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.

Amino Acid Sequence↗
PubMed2003

Regulation of pollen tube growth by Rac-like GTPases.

Plant Rac-like GTPases have been classified phylogenetically into two major groups-class I and class II. Several pollen-expressed class I Rac-like GTPases have been shown to be important regulators of polar pollen tube growth. The functional participation by some of the class I and all of the class II Arabidopsis Rac-like GTPases in pollen tube growth remains to be explored. It is shown that at least four members of the Arabidopsis Rac GTPase family are expressed in pollen, including a class II Rac, AtRac7. However, when over-expressed as fusion proteins with GFP, both pollen- and non-pollen-expressed AtRacs interfered with the normal pollen tube tip growth process. These observations suggest that these AtRacs share similar biochemical activities and may integrate into the pollen cellular machinery that regulates the polar tube growth process. Therefore, the functional contribution by individual Rac GTPase to the pollen tube growth process probably depends to a considerable extent on their expression characteristics in pollen. Among the Arabidopsis Racs, GFP-AtRac7 showed association with the cell membrane and Golgi bodies, a pattern distinct from all previously reported localization for other plant Racs. Over-expressing GFP-AtRac7 also induced the broadest spectrum of pollen tube growth defects, including pollen tubes that are bifurcated, with diverted growth trajectory or a ballooned tip. Transgenic plants with multiple copies of the chimeric Lat52-GFP-AtRac7 showed severely reduced seed set, probably many of these defective pollen tubes were arrested, or reduced in their growth rates that they did not arrive at the ovules while they were still receptive for fertilization. These observations substantiate the importance of Rac-like GTPases to sexual reproduction.

Arabidopsis↗
PubMed2003

AtCSLA7, a cellulose synthase-like putative glycosyltransferase, is important for pollen tube growth and embryogenesis in Arabidopsis.

The cellulose synthase-like proteins are a large family of proteins in plants thought to be processive polysaccharide beta-glycosyltransferases. We have characterized an Arabidopsis mutant with a transposon insertion in the gene encoding AtCSLA7 of the CSLA subfamily. Analysis of the transmission efficiency of the insertion indicated that AtCSLA7 is important for pollen tube growth. Moreover, the homozygous insertion was embryo lethal. A detailed analysis of seed developmental progression revealed that mutant embryos developed more slowly than wild-type siblings. The mutant embryos also showed abnormal cell patterning and they arrested at a globular stage. The defective embryonic development was associated with reduced proliferation and failed cellularization of the endosperm. AtCSLA7 is widely expressed, and is likely to be required for synthesis of a cell wall polysaccharide found throughout the plant. Our results suggest that this polysaccharide is essential for cell wall structure or for signaling during plant embryo development.

Amino Acid Sequence↗