Nodulation development

Figure 1 Communication between microsymbiont and legume during the early stages of nodule development. (From Ref. 4.)...

In older patients toxic multinodular goiter typically presents as longstanding asymptomatic multinodular goiters. Functional autonomy of the nodules develops over time by an unknown mechanism and causes the disease to move from the nontoxic to the toxic phase. The onset of hyperthyroidism is gradual, and the symptoms are usually milder than those of Graves disease. 

Yang, W.C. et al.. In situ localization of chalcone synthase mRNA in pea root nodule development, Plant J., 2, 143, 1992. 

Soil-borne bacteria of the family Rhizobiaceae and leguminous plants form a symbiotic relationship during which a new organ, the root nodule, is developed. Within these root nodules the bacteria fix atmospheric dinitrogen and the product of nitrogen fixation, ammonia, is exported to the plant [69,70]. Root nodules develop from primordia which are established at specific sites in the root cortex shortly after Rhizobium infection. The peptide enod40 is believed to play a critical role in inducing the de-differentiation and the mitotic division of root cortical cells, i.e. the initial steps in nodule development. This however, is not entirely undisputed [3,4,69-72]. 

Studies on the white clover -Rhizobium trifolii interaction are the most advanced. Trifoliin A, a lectin present in clover-seedling roots, binds hapten reversibly to carbohydrate antigens cross-reactive on the capsular polysaccharide of R. trifolii and clover epidermal-cells.244 A specific hapten that inhibits binding of trifoliin A to both surfaces is 2-deoxy-D-arabino-hexose.245 It has also been shown that levels of trifoliin A on root hairs decline with increasing concentrations of nitrate, in parallel to root-nodule development,246 and that lectin receptors are transient on R. trifolii, in a way coinciding with its capacity to be adsorbed to clover roots.247... 

Fig. 4. Changes in A, GS mRNAs and B, GS isoenzymes, during nodule development. The abundances of the mRNAs were measured by an RNase protection technique and the isoenzymes following separation by IEX-HPLC (adapted from Cullimore et al., 1990). GSs=GS synthetase activity. The isoenzymes are as defined in Fig. 3.

Besides the abundant nodulins like Lb, GS, uricase and sucrose synthetase, many other enzymes involved in nodule metabolism are induced during the course of nodule development (see Verma Nadler, 1984). However, owing to the relatively low abundance of these enzymes and their mRNAs in nodules, none of the cognate genes have been cloned and new cloning strategies need to be employed to isolate these relatively less abundantly expressed nodulin sequences. 

Fig. 3. Three distinct groups of signals produced during infection and nodule development inducing early and late nodulin genes.

Konieczny, A., Szczyglowski, K., Boron, L., Przybylska, M. Legocki, A.B. (1988). Expression of lupin nodulin genes during root nodule development. Plant Science 55, 145-9. 

Lara, M., Cullimore, J.V., Lea, P.J., Miflin, B.J., Johnston, A.W.B. Lamb, J.W. (1983). Appearance of a novel form of plant glutamine synthetase during nodule development in Phaseolus vulgaris L. Planta 157, 254-8. 

Sengupta-Gopalan, C. Pitas, J.W. (1986). Expression of nodule-specific glutamine synthetase genes during nodule development in soybeans. Plant Molecular Biology 7, 189-99. 

Verma, D.P.S. Fortin, M.G. (1989). Nodule development and formation of the endosymbiotic compartment. In Cellular and Somatic Cell Genetics of Plants, Vol. 6, The Molecular Biology of Nuclear Genes, ed. J. Schell l.K. Vasil, pp. 329-53. San Diego, CA Academic Press. 

D Antuono, A.L., Casabuono, A., Couto, A., Ugalde, R.A., Lepek, V.C. Nodule development induced by Mesorhizobium loti mutant strains affected in polysaccharide synthesis. Mol Plant-Microbe Interact 18 (2005) 446-457. 

Kosslak, R.M., Bohlool, B.B. Suppression of nodule development on one side of a split root system of soybean caused by a prior inoculation of the other side. Plant Physiol 75 (1984) 125-130. 

Perotto, S., VandenBosch, K.A., Butcher, G.W., Brewin, N.J. Molecular composition and development of the plant glycocalyx associated with the peribacteroid membrane of pea root nodules. Development 112 (1991) 763-773. 

D Haeze W, Holsters M. Nod factor structures, responses, and perception during initiation of nodule development. Glycobiol-... 

The Rhizobium occurs in specialized nodules on the roots of the legumes. These are developed when the soildwelling Rhizobium invades a root hair, stimulating the plant to form a nodule. Nodule development is inhibited in acidic soils and if the concentrations of nitrate in soil are large. To protect the nitrogenase enzyme, the interior... 

Chalky or powdery Fine loose powder of calcium carbonate as a continuous body with little or no nodule development, consisting of micrite or microspar, with etched silicate grains, peloids and root and fungal-related microfeatures. Commonly is a transitional zone from calcareous soil to nodular horizons... 

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