Cell adhesion activity for murine carcinoma cells of a wheat germ 55-kDa protein with binding affinity for animal extracellular matrix proteins

A wheat germ 55-kDa protein was isolated by affinity chromatography with Matrigel immobilized on agarose, followed by preparative gel electrophoresis. This Matrigel-binding protein designated as WG-55 had an amino-terminal amino acid sequence which is identical to that of a putative mature form of wheat storage protein Gbl 1. WG-55 reacted with concanavalin A, indicating its glycoprotein nature as expected from the amino acid sequence of Gbl 1. As expected, similarly, WG-55 exhibited RGD-dependent cell adhesion activity for murine carcinoma cells. These data suggest that WG-55 or mature Gbl 1 protein may play a role in plant cell adhesion.     

A higher plant extracellular vitronectin-like adhesion protein is related to the translational elongation factor-1 alpha.

Higher plant proteins immunologically related to the animal substrate adhesion molecule vitronectin have recently been observed and implicated in a variety of biological processes, such as plasma membrane-cell wall adhesion, pollen tube extension, and bacterium-plant interaction. We provide evidence that, similar to vitronectin, one of these proteins, PVN1 (plant vitronectin-like 1), isolated from 428 mM NaCl-adapted tobacco cells binds to glass surfaces an heparin. PVN1 was isolated by glass bead affinity chromatography. Isolated PVN1 has adhesive activity based on results from a baby hamster kidney cell-spreading assay. This plant adhesion protein was detected in all tissues examined but was most abundant in roots and salt-adapted cultured cells. Immunogold labeling indicated that PVN1 is localized in the cell wall of cortical and transmitting tissue cells of pollinated mature styles. A partial amino acid sequence of PVN1 revealed no similarity with vitronectin but, instead, was nearly identical to the translational elongation factor-1 alpha (EF-1 alpha). A clone isolated by screening a tobacco cDNA expression library with anti-PVN1 encoded a protein with greater than 93% identity to sequences of EF-1 alpha from plants of numerous species. Immunological cross-reactivity between tobacco PVN1 and EF-1 alpha as well as the reaction between the EF-1 alpha antibody and the 65- and 75-kD vitronectin-like proteins of a fucoidal alga supported the conclusion that the plant extracellular adhesion protein PVN1 is related to EF-1 alpha.     

cDNA sequence of the human integrin beta 5 subunit

A novel integrin receptor involved in cell adhesion to the matrix protein vitronectin has recently been described from a human lung epithelial-derived cell line (Cheresh, D. A., Smith, J. W., Cooper, H. M., and Quaranta, V. (1989) Cell 57, 59-69). This receptor has an alpha subunit that appears identical to the alpha v of the vitronectin receptor alpha v beta 3 expressed in melanoma and endothelial cells, but is complexed with a distinct beta subunit, beta 5. cDNA clones coding for beta 5 have been isolated and used to determine the mRNA and amino acid sequence of this new subunit. A 3.3-kilobase mRNA was found to code for a mature protein of 775 amino acid residues with a hydrophobic leader sequence of 24 amino acids. A 56% identity was found between the beta 5 and beta 3 protein sequences, making them the most closely related of the integrin beta subunits. Polymerase chain reaction abundance analysis revealed that alpha v and beta 5 mRNAs were found in seven very different cell lines, compared with beta 3 mRNA which was found in only three of the them, indicating that this new integrin receptor may be widely distributed.     

Expression of human growth hormone in transgenic rice cell suspension culture

Human growth hormone (hGH), a pituitary-derived polypeptide, evidences a wide range of biological functions, including protein synthesis, cell proliferation, and metabolism. A synthetic hGH gene (shGH) has been synthesized on the basis of plant-optimized codon usage via an overlap PCR strategy and located in a plant expression vector under the control of the rice amylase 3D (Ramy3D) promoter, which is induced by sugar starvation. The plant expression vector was introduced into rice calli (Oryza sativa L. cv. Donjin) via particle bombardment transformation methods. The integration of the shGH gene into the chromosome of the transgenic rice callus was verified via genomic DNA PCR amplification and shGH expression in transgenic rice suspension cells was confirmed via Northern blot analysis. The shGH protein was detected in the transgenic rice cell suspension culture medium following induction with sugar starvation, using Western blot analysis. The quantity of shGH that accumulated in the transgenic rice cell suspension medium was 57 mg/l. The shGH accumulated in the transgenic rice cell suspension culture medium evidenced a biological activity similar to that of Escherichia coli-derived recombinant hGH. These results indicate that the shGH was generated and accumulated in the transgenic rice cell suspension culture medium, and manifested biological activity.     

Existence of a plant tyrosylprotein sulfotransferase: novel plant enzyme catalyzing tyrosine O-sulfation of preprophytosulfokine variants in vitro

An in vitro assay system to detect tyrosylprotein sulfotransferase (TPST) activity of higher plant cells was established, using synthetic oligopeptides based on the deduced amino acid sequence of a phytosulfokine-alpha (PSK-alpha) precursor. TPST activity was found in microsomal membrane fractions of rice, asparagus and carrot cells and it was confirmed that acidic amino acid residues adjacent to the tyrosine residues of acceptor peptides were essential to the sulfation reaction. The asparagus TPST exhibited a broad pH optimum of 7.0-8.5, required manganese ions for maximal activity and appeared to be a membrane-bound protein localized in the Golgi apparatus. These enzymes should be defined as a new class of plant sulfotransferases that catalyze tyrosine O-sulfation of a PSK-alpha precursor and other unknown proteins.     

Physiological Processes Contributing to the Difference in Grain Amino Acid Content between Two Hybrid Rice (Oryza sativa L.) Cultivars

Improving grain amino acid content of rice (Oryza sativa L.) is essential for the health of consumers. This study was conducted to identify the physiological processes that contribute to the higher grain amino acid content in hybrid rice cultivar Lingliangyou 268 compared to Luliangyou 996. The results showed that total amino acid content in grains was 9% higher in Lingliangyou 268 than in Luliangyou 996. There was no significant difference in grain nitrogen (N) content between Lingliangyou 268 and Luliangyou 996, while ratio of amino acid to N was 6% higher in Lingliangyou 268 compared to Luliangyou 996. A total of 16 differentially expressed proteins related to amino acid metabolism (e.g., erythronate-4-phosphate dehydrogenase domain containing protein) were identified in grains between Lingliangyou 268 and Luliangyou 996. The identified proteins were involved in 10 molecular functions. Six of the 10 defined functions were related to binding (heterocyclic compound binding, nucleoside phosphate binding, nucleotide binding, organic cyclic compound binding, protein binding, and small molecule binding) and the other 4 defined functions were catalytic activity, enzyme regulator activity, hydrolase activity, and transferase activity. These results indicate that the higher grain amino acid content in Lingliangyou 268 compared to Luliangyou 996 is attributed to increased efficiency of converting N to amino acid that results from altered expression of proteins related to amino acid metabolism.     

Identification, cDNA cloning, and gene expression of soluble starch synthase in rice (Oryza sativa L.) immature seeds.

Three forms of soluble starch synthase were resolved by anion-exchange chromatography of soluble extracts from immature rice (Oryza sativa L.) seeds, and each of these forms was further purified by affinity chromatograph. The 55-, 57-, and 57-kD proteins in the three preparations were identified as candidates for soluble starch synthase by western blot analysis using an antiserum against rice granule-bound starch synthase. It is interesting that the amino-terminal amino acid sequence was identical among the three proteins, except that the 55-kD protein lacked eight amino acids at the amino terminus. Thus, these three proteins are products of the same gene. The cDNA clones coding for this protein have been isolated from an immature rice seed library in lambda gt11 using synthetic oligonucleotides as probes. The deduced amino acid sequence of this protein contains a lysine-X-glycine-glycine consensus sequence for the ADP-glucose-binding site of starch and glycogen synthases. Therefore, we conclude that this protein corresponds to a form of soluble starch synthase in immature rice seeds. The precursor of the enzyme contains 626 amino acids, including a 113-residue transit peptide at the amino terminus. The mature form of soluble starch synthase shares a significant but low sequence identity with rice granule-bound starch synthase and Escherichia coli glycogen synthase. However, several regions, including the substrate-binding site, are highly conserved among these three enzymes. Blot hybridization analysis demonstrates that the gene encoding soluble starch synthase is a single-copy gene in the rice genome and is expressed in both leaves and immature seeds. These results suggest that soluble and granule-bound starch synthases play distinct roles in starch biosynthesis of plant.     

Expression pattern, subcellular localization and structure--function relationship of rat Tpx-1, a spermatogenic cell adhesion molecule responsible for association with Sertoli cells

The gene for a testicular cell adhesion protein called Tpx-1, which mediates the binding of spermatogenic cells to Sertoli cells of the rat in primary culture, was previously cloned. Here the characterization of Tpx-1 is reported. Tpx-1 messenger ribonucleic acid (mRNA) became detectable in pachytene spermatocytes and continued to be present throughout development into elongated spermatids, while the amount of Tpx-1 protein seemed to increase some time after the increment of mRNA. Tpx-1 protein was also present, although less abundantly, in spermatozoa prepared from the epididymis. Tpx-1 contains a cluster of hydrophobic amino acid residues near the amino terminus and a cysteine-rich region in the carboxyl-terminal half. Tpx-1 fused with green fluorescence protein was secreted into the medium when expressed in a cultured cell line, depending on the presence of the amino-terminal hydrophobic region. Moreover, Tpx-1 was present in the medium of testicular cell primary culture. Structure-function analysis revealed that the amino-terminal 101 amino acid residues were sufficient for cell adhesion activity, whereas the carboxyl-terminal cysteine-rich region was dispensable. In conclusion, Tpx-1 is produced and secreted from spermatogenic cells at various differentiation stages, and mediates the interaction of those cells with Sertoli cells.     

Internal Zinc Accumulation Is Correlated with Increased Growth in Rice Suspension Culture

A high zinc concentration of 520 μm, approximately 100 times that used most often in standard plant tissue culture media, was found to be superior in liquid callus cultures of japonica rice, increasing growth to 146% compared with standard N6 medium. At the same time, the internal zinc concentration increased 40 times in fast growing cells; soluble protein doubled, and free amino acids decreased. Under zinc-free conditions the cultures slowed in growth, and several free amino acids such as aspartic acid, glutamic acid, asparagine, and glutamine accumulated. We suggest that zinc acts as a direct regulatory factor in inducing auxin activity, but not auxin levels, making high internal zinc accumulation mandatory if high auxin concentrations are required as in rice callus cultures. Received July 16, 1997; accepted September 22, 1997     

Cloning and characterization of the gene for a phloem-specific glutathione S-transferase from rice leaves

The N-terminal amino-acid sequence was determined for a major r ice p hloem p rotein with a molecular mass of 31  kDa, named RPP31. The corresponding full-length rice EST-clone was cloned based on the amino acid sequence. The predicted total amino-acid sequence of RPP31 shared high similarity with plant glutathione S -transferases (GSTs). Recombinant RPP31 produced in Escherichia coli and rice phloem sap showed GST activity. Immunocytological analysis indicated that RPP31 is localized in the phloem region of leaves. In mature leaves, the signal was restricted to sieve element–companion cell complexes, and was stronger in sieve elements than in companion cells. Although some plant GSTs are known to be induced by xenobiotics, the amount of RPP31 was not affected by treatments with an herbicide, pretilachlor, and/or its safener, fenclorim. These results suggest that RPP31 is an active GST restricted to the phloem region of normal rice leaves.     

Cell surface anchorage and ligand-binding domains of the Saccharomyces cerevisiae cell adhesion protein alpha-agglutinin, a member of the immunoglobulin superfamily.

alpha-Agglutinin is a cell adhesion glycoprotein expressed on the cell wall of Saccharomyces cerevisiae alpha cells. Binding of alpha-agglutinin to its ligand a-agglutinin, expressed by a cells, mediates cell-cell contact during mating. Analysis of truncations of the 650-amino-acid alpha-agglutinin structural gene AG alpha 1 delineated functional domains of alpha-agglutinin. Removal of the C-terminal hydrophobic sequence allowed efficient secretion of the protein and loss of cell surface attachment. This cell surface anchorage domain was necessary for linkage to a glycosyl phosphatidylinositol anchor. A construct expressing the N-terminal 350 amino acid residues retained full a-agglutinin-binding activity, localizing the binding domain to the N-terminal portion of alpha-agglutinin. A 278-residue N-terminal peptide was inactive; therefore, the binding domain includes residues between 278 and 350. The segment of alpha-agglutinin between amino acid residues 217 and 308 showed significant structural and sequence similarity to a consensus sequence for immunoglobulin superfamily variable-type domains. The similarity of the alpha-agglutinin-binding domain to mammalian cell adhesion proteins suggests that this structure is a highly conserved feature of adhesion proteins in diverse eukaryotes.     

Isolation and Characterization of a Relatively Guanine-specific Endoribonuclease in Rice Bran

A relatively guanine-specific endoribonuclease (RB-1) was isolated from rice bran. The pH optimum was 8.5 using yeast RNA as a substrate. The enzyme activity was inhibited by Cu²⁺, Zn²⁺, DTT and SDS, while EDTA, PCMB, IAA and heparin had no effect on the activity. The enzymic activity of RB-1 was inhibited by 3′-GMP as an end-product inhibitor. The enzyme protein was highly heat-stable. RB-1 did not hydrolyze native calf thymus DNA, heat-denatured DNA, poly A, poly U and poly C. Among synthetic substrates, only poly I was depolymerized. Only 2′,3′-cyclic GMP was identified in the hydrolysate of yeast RNA after 6hr hydrolysis.     

Cloning and characterization of a jasmonic acid-responsive gene encoding 12-oxophytodienoic acid reductase in suspension-cultured rice cells

In suspension-cultured rice ( Oryza sativaL.) cells, jasmonic acid (JA) functions as a signal transducer in elicitor N-acetylchitoheptaose-induced phytoalexin production. Differential screening of a cDNA library constructed using poly(A)(+) RNA from suspension-cultured rice cells treated with JA (10(-4) M) for 2 h yielded a cDNA for a gene that responded to exogenous JA by an increase in mRNA level. Nucleotide sequence analysis indicated that the cDNA encodes an homologue of the yeast Old Yellow Enzyme. The deduced amino acid sequence was very similar to the sequences of 12-oxophytodienoic acid reductases (OPR) 1 and 2 from Arabidopsis thaliana(AtOPR1 and AtOPR2) and OPR1 from tomato ( Lycopersicon esculentum) (LeOPR1). The cDNA-encoded protein purified from recombinant Escherichia coli cells as a hexahistidine-tagged fusion protein exhibited OPR activity similar to that of AtOPR1, AtOPR2, and LeOPR1, which catalyze reduction of (-)- cis-12-oxophytodienoic acid (OPDA) preferentially over (+)- cis-OPDA, a natural precursor of JA. Thus the rice enzyme was termed OsOPR1. The physiological roles of OsOPR1 are discussed. This is the first report of the cloning of an OPR gene from a monocot plant.     

Differential regulation of cellular adhesion and migration by recombinant laminin-5 forms with partial deletion or mutation within the G3 domain of alpha3 chain

The basement membrane protein laminin-5 promotes cell adhesion and migration. The carboxyl-terminal G3 domain in the alpha3 chain is essential for the unique activity of laminin-5. To investigate the function of the G3 domain, we prepared various recombinant laminin-5 forms with a partially deleted or mutated G3 domain. The deletion of the carboxyl-terminal 28 amino acids (region III) markedly decreased the cell adhesion activity with a slight loss of the cell motility activity toward BRL and EJ-1 cells. This change was attributed to the loss of Lys-Arg-Asp sequence. Further deletion of 83 amino acids (region II) led to almost complete loss of the cell motility activity. All charged amino acid residues tested in this region were not responsible for the activity loss. These results suggest that the G3 domain contains two distinct regions that differently regulate cell adhesion and migration. Analysis of laminin-5 receptors showed that integrins alpha3beta1, alpha6beta1, and alpha6beta4 had different but synergistic effects on cell adhesion and migration on laminin-5. However, the structural change of the G3 domain appeared not to change integrin specificity. The present study demonstrates that the G3 domain in laminin-5 plays a central role to produce different biological effects on cells.