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Query: UNIPROT:P06889 (Mol)
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Complementary DNA clones encoding acidic and basic isoforms of the class III chitinase were isolated from Nicotiana tabacum. The clones share ca. 65% identity, are equally homologous to the class III chitinases from cucumber and Arabidopsis, and are members of small gene families in tobacco. An acidic class III chitinase was purified from the intercellular fluid of tobacco leaves infected with tobacco mosaic virus (TMV). Partial amino acid sequencing of the protein confirmed that it was encoded by one of the cDNA clones. The mRNAs of the class III chitinases are coordinately expressed in response to TMV infection, both in infected and uninfected tissue. The acidic and basic class III chitinases constitute previously undescribed pathogenesis-related proteins in tobacco.
Plant Mol Biol 1992 Aug
PMID:Acidic and basic class III chitinase mRNA accumulation in response to TMV infection of tobacco. 164 80

Vacuolar class I beta-1,3-glucanases (EC 3.2.1.39) are believed to be important in the induced defense reaction of plants to fungal infection. We used antisense transformation to test this hypothesis and to identify other possible physiological functions of this enzyme. Nicotiana sylvestris plants were transformed with antisense constructions containing the region from position 27 to 608 of the coding sequence of the basic, vacuolar beta-1,3-glucanase gene GLA of tobacco regulated by cauliflower mosaic virus 35S RNA expression signals. Plants homozygous for this transgene showed a marked, ca. 20-fold reduction in the constitutive expression of class I beta-1,3-glucanase antigen in their leaves. RNA blot analysis indicated that the antisense plants expressed low levels of the sense transcript of the host beta-1,3-glucanase gene and the antisense transcript of the transgene. Immune blot analysis of plant extracts indicated that only expression of the N. sylvestris homologue of class I tobacco beta-1,3-glucanase and not the acidic, class II isoforms of the enzyme was blocked in the antisense plants. Class I isoforms of beta-1,3-glucanase and chitinase were coordinately induced in leaves of untransformed and empty-vector-transformed N. sylvestris plants treated with ethylene or infected with the fungal leaf pathogen Cercospora nicotianae. In antisense plants, chitinase but not beta-1,3-glucanase was induced under these conditions indicating that antisense transformation effectively blocks constitutive as well as induced expression of class I beta-1,3-glucanase. Under greenhouse conditions, antisense plants developed normally and were fertile. The plants did not exhibit increased susceptibility to C. nicotianae infection. These results suggest that expression of the beta-1,3-glucanase isoform blocked by antisense transformation is not necessary for 'housekeeping' functions of N. sylvestris nor defense against the fungal pathogen tested.
Plant Mol Biol 1992 Aug
PMID:The function of vacuolar beta-1,3-glucanase investigated by antisense transformation. Susceptibility of transgenic Nicotiana sylvestris plants to Cercospora nicotianae infection. 164 83

The extracellular, acidic pathogenesis-related protein, PR-4, was purified to homogeneity from leaves of Nicotiana tabacum infected with tobacco mosaic virus (TMV) and characterized by partial amino acid sequencing. Complementary DNA clones encoding PR-4 were isolated using an oligonucleotide probe based on the sequence of one of the peptides. The deduced PR-4 protein sequence was found to be related to a family of proteins including hevein and Win-1, which have an amino-terminal lectin domain and a carboxy-terminal domain of unknown function. PR-4 is homologous to the carboxy-terminus of these proteins but does not contain the lectin domain. Thus, the organization of the PR-4 family of proteins is similar to that of the plant chitinase family, in that both contain structural subclasses characterized by the presence or absence of an amino-terminal lectin domain. This observation is consistent with the proposal that the DNA encoding the lectin domain may be capable of transposing to form new genes encoding proteins of more complex, multi-domain structure. The expression of PR-4 mRNA was found to increase dramatically in response to TMV infection and the time course of RNA accumulation was similar to that of other PR proteins.
Mol Gen Genet 1991 Nov
PMID:Pathogenesis-related protein 4 is structurally homologous to the carboxy-terminal domains of hevein, Win-1 and Win-2. 174 23

The amino acid sequences of peptides generated by trypsin and chymotrypsin digestions of the acidic PR4 chitinase from bean were determined. Oligonucleotide primers derived from this sequence were used to synthesize a PR4 chitinase-specific probe by PCR-amplification. This probe allowed the isolation of cDNA clones encoding PR4 chitinase that have been sequenced. This acidic and extracellular chitinase shows some homology to the basic isoform from the same plant, and differs from other known acidic chitinases by the presence of an amino-terminal cysteine-rich domain. Southern blot analysis of bean genomic DNA revealed that PR4 chitinase is encoded by a single gene.
Plant Mol Biol 1991 Aug
PMID:Isolation of a complementary DNA encoding the bean PR4 chitinase: an acidic enzyme with an amino-terminus cysteine-rich domain. 186 76

Endochitinases (E.C.3.2.14, chitinase) are believed to be important in the biochemical defense of plants against chitin-containing fungal pathogens. We introduced a gene for class I (basic) tobacco chitinase regulated by Cauliflower Mosaic Virus 35S-RNA expression signals into Nicotiana sylvestris. The gene was expressed to give mature, enzymatically active chitinase targeted to the intracellular compartment of leaves. Most transformants accumulated extremely high levels of chitinase-up to 120-fold that of non-transformed plants in comparable tissues. Unexpectedly, some transformants exhibited chitinase levels lower than in non-transformed plants suggesting that the transgene inhibited expression of the homologous host gene. Progeny tests indicate this effect is not permanent. High levels of chitinase in transformants did not substantially increase resistance to the chitin-containing fungus Cercospora nicotiana, which causes Frog Eye disease. Therefore class I chitinase does not appear to be the limiting factor in the defense reaction to this pathogen.
Plant Mol Biol 1991 Jan
PMID:High-level expression of a tobacco chitinase gene in Nicotiana sylvestris. Susceptibility of transgenic plants to Cercospora nicotianae infection. 188 92

Synthetic oligonucleotides based on similarity between tobacco 1,3-beta-D-glucanase and barley 1,3-1,4-beta-D-glucanase were used to prime the synthesis and amplification of a 162 bp bean (Phaseolus vulgaris L.) beta-glucanase cDNA by the polymerase chain reaction (PCR). The PCR product was used to isolate a near full-length beta-glucanase cDNA corresponding to an approximately 1400 bp full-length transcript, from a library containing cDNA sequences complementary to mRNA from fungal elicitor-treated bean cells. At the amino acid level, the bean beta-glucanase cDNA was 59% similar to tobacco 1,3-beta-D-glucanase, 46% similar to barley 1,3-beta-D-glucanase and 46% similar to barley 1,3-1,4-beta-D-glucanase. At the nucleotide level, the similarities were 65, 50 and 53% respectively. The beta-glucanase appeared to be encoded by a single gene with similar genomic organization in bean cultivars Canadian Wonder, Imuna and Saxa. On the basis of predicted Mr, isoelectric point, sequence similarity, and comparisons of rate of transcript appearance with induced enzyme activity, it was concluded that the cDNA encodes the basic bean endo-1,3-beta-D-glucanase. Glucanase transcripts were induced, from very low basal levels, with similar kinetics to chitinase transcripts in elicitor-treated bean cell suspension cultures.
Plant Mol Biol 1991 Jan
PMID:cDNA cloning and characterization of a putative 1,3-beta-D-glucanase transcript induced by fungal elicitor in bean cell suspension cultures. 190 91

Poplar trees have at least two different chitinase genes, win6 and win8, which are systemically wound-inducible and belong to multigene families [Proc Natl Acad Sci USA 86: 7895-7899]. On one genomic clone that we have partially sequenced, there are three win6 genes which are transcriptionally oriented in the same direction. Between two of the win6 genes is a gene that we have designated chitinase X (chiX), which appears to be a pseudogene belonging to a multigene family distinct from win6 and win8. The win6 and chiX genes we have sequenced contain two AT-rich introns that correspond in location to those in a basic chitinase gene from tobacco. The predicted Win6 proteins have a putative signal peptide, a cysteine-rich 'hevein' domain, a hinge region, and a catalytic domain as described in Shinshi et al. [Plant Mol Biol 14: 357-368]. The predicted Win8 protein, by contrast, completely lacks a hinge region. Both Win6 and Win8 are expected to be highly acidic (with a calculated net charge of -15 to -17), whereas ChiX proteins are likely to be basic. Based on an inferred phylogeny, the catalytic domain of ChiX is more closely related to the basic chitinases of herbaceous plants than are either Win6 or Win8.
Plant Mol Biol 1991 Oct
PMID:Populus chitinase genes: structure, organization, and similarity of translated sequences to herbaceous plant chitinases. 191 89

The endochitinases (E.C. 3.2.1.14, chitinase) are a structurally diverse group of enzymes believed to be important in the biochemical defense of plants against potential pathogens. The gene for a chitinase of Nicotiana tabacum L. cv. Havana 425 has been cloned and sequenced. The major transcription start is 11 bp upstream of the ATG codon and 28 bp downstream of the TATA box. The gene contains two introns and encodes a basic chitinase of 329 amino acids with a 23 amino acid N-terminal signal peptide followed by a 43 amino acid, cysteine-rich domain, which is linked by a hinge region to the main structure of the enzyme. This gene appears to be expressed because the exons are identical to the coding sequence of a cDNA which was isolated. Comparison of chitinase amino acid sequences from different plants indicates there are at least three classes of these enzymes: class I, basic chitinases with an N-terminal cysteine-rich domain and a highly conserved main structure; class II, chitinases similar to the main structure of class I chitinases but lacking the cysteine-rich domain; and, class III, chitinases with conserved sequences different from those of the class I and II enzymes. The sequences encoding the cysteine-rich domain in class I chitinases are flanked by 9-10 bp imperfect direct repeats suggesting that these domains arose from a common ancestral gene and were introduced into genes for class I enzymes by transposition events.
Plant Mol Biol 1990 Mar
PMID:Structure of a tobacco endochitinase gene: evidence that different chitinase genes can arise by transposition of sequences encoding a cysteine-rich domain. 196 83

Chitinases are believed to play an important role in plant defence against bacterial and fungal attack. In peanut (Arachis hypogaea) chitinase genes form a small multigene family. Four chitinase cDNAs (chit 1-4) were isolated from cultured peanut cells. Expression of individual chit genes was assayed by the polymerase chain reaction (PCR) followed by analysis of restriction fragment length polymorphisms (RFLP). UV irradiation, dilution of cell cultures and treatment with Phytophthora megasperma (Pmg) elicitor or yeast extract were used to induce expression of chit genes. The chit 3 gene is constitutively expressed at a low level in untreated as well as in treated cultures; the expression of chit 4 gene is induced by each of the stimuli tested, whereas the chit 1 gene is activated by cell culture dilution and by yeast extract treatment. The chit 2 gene is strongly activated by treatment with cell wall components from the fungus Phytophthora megasperma but not by the other stimuli. These results indicate that chit 2 gene expression may be controlled by pathogen-specific regulatory elements.
Mol Gen Genet 1990 Dec
PMID:Elicitor-specific induction of one member of the chitinase gene family in Arachis hypogaea. 198 4

Chitinase, which catalyzes the hydrolysis of the beta-1,4-N-acetyl-D-glucosamine linkages of the fungal cell wall polymer chitin, is involved in inducible defenses of plants. A basic chitinase genomic sequence was isolated from a rice (Oryza sativa L.) genomic library using a bean chitinase gene fragment as a probe. The complete nucleotide sequence of the rice chitinase RCH10 gene was determined, and shown to contain an open reading frame with no introns, encoding a polypeptide of 336 amino acids. This polypeptide consists of a 21 amino acid signal peptide, a hevein domain, and a chitinase catalytic domain. The RCH10 gene has 63% identity at the nucleotide level and 75% identity at the amino acid level with chitinase genes from dicotyledonous plants such as bean, potato, and tobacco. A gene fusion of trpE and the coding region of RCH10 expressed in Escherichia coli gave a product that reacted with antiserum to bean chitinase, confirming the identity of RCH10 as a rice chitinase gene. Primer extension analysis identified two transcription start sites 53 bp and 55 bp upstream from the translation initiation codon. The 5' flanking region contains TATA and CAAT boxes, and the 3' region contains an AATAA polyadenylation signal. Southern blot hybridization indicated that there is a family of chitinase genes in the rice genome. Northern blot analysis showed that the RCH10 chitinase gene is induced in suspension cultured cells by a fungal cell wall elicitor. Rice chitinase transcripts accumulate to a high level in roots, but only low levels are found in stem and leaf tissue.
Mol Gen Genet 1991 Apr
PMID:Isolation and characterization of a rice gene encoding a basic chitinase. 203 21


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