Chemistry: natural resins or derivatives; peptides or proteins; – Proteins – i.e. – more than 100 amino acid residues
Patent
1992-05-01
1999-08-03
Fox, David T.
Chemistry: natural resins or derivatives; peptides or proteins;
Proteins, i.e., more than 100 amino acid residues
530370, 530379, 435 691, 435 697, 4351723, 435200, 435418, 435419, 536 234, 536 236, C12N 1529, C12N 924, C12N 1556, C12N 1582, C12N 1562
Patent
active
059326980
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a new recombinant gene coding for a new protein having endochitinase activity or for a precursor thereof, to a bacterium containing this recombinant gene, to a plant cell, a plant or a plant part, especially a plant seed, which contain a recombinant gene of this type, and to a method for rendering plants resistant to pathogenic agents such as fungi and bacteria as well as arthropods, in particular insects, and nematodes, which comprises a step of transformation with this gene, as well as to this new protein and to a method for preparing it.
Crop plants are subjected to attacks by pathogenic agents such as fungi and bacteria, which are responsible for substantial harvest losses. At present, the principal means of controlling these agents lies in the use of chemical substances having fungicidal or bactericidal activity. It is now known that plants react naturally to such attack by various defense mechanisms, which are unfortunately in general triggered too late and at too low an intensity to be sufficiently effective. One of these mechanisms comprises the induction of an enzyme known as chitinase EC 3.2.1.14 (A. Toppan et al., 1982, Agronomie, 2, 829-834). This induction may be artificially stimulated with substances such as ethylene, and results in an increase in resistance of the treated plant to pathogenic agents (Boller T., 1988, Oxford Surveys of Plant Molecular and Cell Biology, 5, 145-174).
Chitin is a linear polysaccharide polymer consisting of N-acetylglucosamine units linked via B-(1.fwdarw.4) bonds. It is a structural compound present in the walls of most pathogenic fungi, in the exoskeleton of arthropods, especially insects, and in the external sheath of the eggs and cysts of nematodes. The enzymes known as chitinases are capable of degrading chitin. Among these, two different groups are distinguished, defined according to their mode of attack of chitin: exochitinases capable of liberating the N-acetylglucosamine unit located at the non-reducing ends of the chains, and endochitinases capable of fragmenting the chains, which are the only chitinases capable of inhibiting in vitro the growth of mycelial hyphae (Roberts W. K. et al., 1988, Gen. Microbiol., 134, 169-176). The great majority of known plant chitinases are of the endo type, in contrast to the known bacterial chitinases which are of the exo type (Roberts W. K. et al., 1988, Gen. Microbiol., 134, 169-176).
A large number of plant endochitinases, in particular those of tomato and tobacco (P. AUDY et al., 1990, Phytochem, 29, 4, 1143-1159), also exhibit a lysozyme activity, a capacity to cleave the .beta.-(1.fwdarw.4) bonds between the N-acetylglucosamine and the N-acetylmuramic acid of the peptidoglycan of bacterial walls. It may hence be acknowledged that lysozyme and endochitinase activities are fairly closely related (Roberts W. K. et al., 1988, Gen. Microbiol., 134, 169-176), and that a new protein having endochitinase activity, especially one of structures intermediate between tomato endochitinase and tobacco endochitinase, probably exhibits lysozyme activity.
DNA sequences coding for bacterial exochitinases have already been isolated and cloned (Jones J. D. G. et al., 1986, EMBO J., 5, 467-473 and Sundheim L. et al., 1988, Physiol. Molec. Plant Pathol., 33, 483-491). U.S. Pat. No. 4,751,081 describes the isolation and cloning of the complete gene coding for Serratia marcescens chitinase, as well as the transformation of Pseudomonas fluorescens NZ130 and Pseudomonas putida MK280 bacteria with this gene. These transformed bacteria are capable of slightly degrading a colloidal chitin dispersed in the bacterial culture medium. The work of Harpster M. H. et al., 1989, Nucl. Ac. Res., 17, 5395 has shown that this gene codes for an exochitinase, thereby explaining the low efficiency of degradation observed (see Table 2, col. 13 and 14 of this document). The publication of Jones J. D. G. et al., (1988), Mol. Gen. Genet., 212, 536-542, mentions the transformation of tobacco plants with Agrobacte
REFERENCES:
Shinshi et al, Plant Molecular Biology, vol. 14, 1990, pp. 357-368.
Durand-Tardif, Pascal Abrege No. 88-0108006.
Linthorst et al, Molecular Plant-Microbe Interactions, vol. 3, No. 4, pp. 252-258.
Gaynor. 1988. Nucleic Acids Research. 16(11):5210.
Laflamme et al. 1989. Plant Molecular Biology. 13:249-250.
Gaynor et al. 1989. Nucleic Acids Research. 17(14):5855-5856.
Hedrick et al. 1988. Plant Physiol. 86:182-186.
Dubois Michel
Grison Rene
Leguay Jean-Jacques
Pignard Annie
Toppan Alain
Fox David T.
Rustica Prograin Genetique
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