The present invention relates to a glucan elicitor receptor, DNA molecules coding for the glucan elicitor receptor, vectors containing the DNA molecules, plant cells transformed with the DNA molecules, fungus-resistant plants transformed with the DNA molecules and a method for creating such plants. More specifically, the present invention relates to a glucan elicitor receptor derived from a soybean root plasma membrane fraction, DNA molecules coding for the glucan elicitor receptor, vectors containing the DNA molecules, plant cells transformed with the DNA molecules, fungus-resistant plants transformed with the DNA molecules and a method for creating such plants.
It is known that plants synthesize and accumulate an antibiotic agent called phytoalexin in response to infection with pathogens (M. Yoshikawa (1978) Nature 257: 546). Some plant pathogens were found to have the substances that induce them to perform such a resistance reaction (N. T. Keen (1975) Science 187: 74), which are called "elicitors". The biochemical process from the infection of plants with pathogens to the synthesis and accumulation of phytoalexin is believed to be as follows:
When the mycelium of a pathogen invades a plant cell, glucanase in the plant cell works so as to cleave polysaccharides on the surface of the pathogen mycelial wall, thereby liberating an elicitor. If the elicitor binds to a receptor in the plant cell, a second messenger which plays a role in signal transduction is produced. The signal transduction substance is incorporated in the nucleus of the plant cell and activates the transcription of the genes coding for phytoalexin synthesize enzymes to induce a phytoalexin synthesis. At the same time, the phytoalexin degradation is inhibited. As a result, phytoalexin is efficiently accumulated in the plant cell.
A phytoalexin playing an important role in the resistance of soybean is called glyceollin and its structure has been determined (M. Yoshikawa et al. (1978) Physiol. Plant. Pathol. 12: 73). Elicitor of soybean has a characteristic structure; it has .beta.-1,6 linked glucan of various lengths as a principal chain from which .beta.-1,3 linked glucan side chains are branched [J. K. Sharp et al. (1984) J. Biol. Chem. 259: 11321; M. Yoshikawa (1990) Plant Cell Technology 1.2: 695]. A receptor specific for a glucan elicitor derived from a soybean pathogenic mold fungus Phytophthora megasperma f. sp. glycinea is believed to be a protein which plays an important role in the synthesis and accumulation of the antibiotic agent glyceollin. A method for the purification of the glucan elicitor receptor specific to this elicitor has been disclosed (E. G. Cosio et al., (1990) FEBS 264: 235, E. G. Cosio et al. (1992) Eur. J. Biochem. 204: 1115, T. Frey et al. (1993) Phytochemistry 32; 543). However, the amino acid sequence of a glucan elicitor receptor has not been determined and the gene coding therefor is not yet known. If a gene coding for glucan elicitor receptor is found, it will be possible to create plants having resistance to pathogenic fungi by incorporating the gene into a chromosome of plants and expressing the glucan elicitor receptor in the plants. Thus, improvement of the productivity of agricultural products can be expected.
An object of the present invention is to provide a glucan elictor receptor.
Another object of the present invention is to provide a DNA molecule coding for a glucan elicitor receptor.
A further object of the present invention is to provide a vector containing a DNA molecule coding for a glucan elicitor receptor.
A still further object of the present invention is to provide a plant cell transformed with a DNA molecule coding for a glucan elicitor receptor.
It is an object of the present invention to provide a plant transformed with a DNA molecule coding for a glucan elicitor receptor.
It is another object of the present invention to provide a method for creating a plant transformed with a DNA molecule coding for a glucan elicitor receptor.