CSDB: Search results

References to other databases: GlycomeDB:28175, CCSD:35814, CBank-STR:8686
Structural formula & atomic coordinates
Sweet-II 3D model
Show glycosyltransferases

The interaction between soil bacteria belonging to the genera Rhizobium, Bradyrhizobium and Azorhizobium and leguminous plants results in the induction of a new plant organ, the root nodule. After invading these root nodules via infection threads the bacteria start to fix atmospheric nitrogen into ammonia which is beneficial for the host plant. This symbiotic interaction is highly host-specific in that each rhizobial strain is able to associate with only a limited number of host plant species. The subject of this presentation is the molecular mechanism by which the bacterium determines its host-specific characteristics. This mechanism appears to be based on at least two stages of molecular signaling between the bacterium and the plant host. In the first stage, flavonoids secreted by the plant root induce, in a host specific way, the transcription of bacterial genes which are involved in nodulation, the so-called nod genes. This leads to the second step of the signaling system: the production and secretion of lipo-oligosaccharide molecules by the Rhizobium bacteria. These signal molecules, which are acylated forms of small fragments of chitin, have various discernable effects on the roots of the host plants. One of these effects is the dedifferentiation of groups of cells located in the cortex which leads to the formation of nodule meristems. In their mitogenic activity the bacterial signals resemble several well-known plant hormones like auxins and cytokinins. However, there are two major differences: (i) the bacterial signals lead to the induction of a specific organ and (ii) they are host-specific in that only the signals produced by compatible bacteria are able to induce meristems. The nod genes determine this stage of host specificity by their essential role in the biosynthesis of the signal molecules. They appear to encode enzymes which are involved in the processes of fatty acid biosynthesis, fatty acid transfer, chitin synthesis and chitin modification. I will illustrate the statement that the nod gene products are ideal model enzymes for the study of these important processes because they are not needed in the free-living state of the bacteria.

symbiosis, plant-microbe interaction, nodulation genes, signal molecules

NCBI PubMed ID: 7718036
Publication DOI: 10.1007/BF00871750
Journal NLM ID: 0372625
Publisher: Dordrecht: Kluwer Academic
Institutions: Institute of Molecular Plant Sciences, Clusius Laboratory, Leiden University, Leiden, The Netherlands

References to other databases: CCSD:46018, CBank-STR:10170
Structural formula & atomic coordinates
Sweet-II 3D model
Show glycosyltransferases

The legume-rhizobia symbiosis is estimated to fix per annum as much nitrogen as the fertilizer industry and is of great agronomic and ecological importance. This efficient nitrogen-fixing association occurs as a result of the formation of a new specialized organ, the root nodule, which is induced by the prokaryotic symbiont on its specific plant partner (see Nap and Bisseling, 1990). The rhizobial genes that determine the host recognition and nodulation have recently been found to specify the synthesis of excreted lipo-oligosaccharide signals (Figure 1) which are capable of eliciting, at extremely low concentrations, many of the plant responses characteristic of the bacteria themselves. These responses include the initiation of cell division, induction of specific changes in cell morphology, and triggering of a plant organogenic program leading to the formation of the nodule. This review focuses on the role of this new class of signaling molecules in host-partner recognition and nodule development in the legume-rhizobia symbiosis.

NCBI PubMed ID: 8402884
Publication DOI: 10.1016/0092-8674(93)90717-5
Journal NLM ID: 0413066
Publisher: Cambridge, MA: Cell Press
Institutions: Laboratoire de Biologie Moléculaire, des Relations Plantes-Microorganismes CNRS-INRA, Castanet-Tolosan, France

References to other databases: CCSD:50015, CBank-STR:10158
Structural formula & atomic coordinates
Sweet-II 3D model
Show glycosyltransferases

The role of oligosaccharide molecules in plant development is discussed. In particular the role of the rhizobial lipo-chitin oligosaccharide (LCO) signal molecules in the development of the root nodule indicates that oligosaccharides play an important role in organogenesis in plants. Recent results of the analyses of structures and of the biosynthesis of the LCO molecules are summarized in this paper. The knowledge and technologies that resulted from these studies will be important tools for further studying the function of LCO signals in the plant and in the search for analogous signal molecules produced by plants.

NCBI PubMed ID: 7858197
Publication DOI: 10.1007/BF00016482
Journal NLM ID: 9106343
Publisher: Dordrecht: Kluwer Academic
Institutions: Institute of Molecular Plant Sciences, Leiden University, The Netherlands