Root nodule development: origin, function and regulation of nodulin genes

Abstract

M. 1992. Root nodule development: origin, function and regulation of nodulin genes. -Physiol. Plant. 85: 253-265,The symbiotic root nodule, an organ formed on leguminous plants, is a product of successful interactions between the host plant and the soil bacteria, Rhizobium spp. Plant hormones play an important role in the genesis of this organ. The hormonal balance appears to be modulated by the signals produced by bacteria. Many host genes induced during nodule organogenesis and the symbiotic state have been identified and characterized from several legumes. These genes encode nodule-specific proteins (nodulins) which perform diverse functions in root nodule development and metabolism. Formation of a subcellular compartment housing the bacteria is essential to sustain the symbiotic state, and several nodulins are involved in maintaining the integrity and function of this compartment. The bacteroid enclosed in the perbacteroid membrane behaves as an 'organelle,' completely dependent on the host for all its requirements for carbon, nitrogen and other essential elements. Thus it seems likely that the nodulins in the peribacteroid membrane perform specific transport functions. While the function of a few other nodulins is known (e.g. nodulin-100, nodulin-35), a group of uncharacterized nodulins exists in soybean root nodules. These nodutins share structural similarities and seem to have been derived from a common ancestor. Induction of nodulin genes occurs prior to and independent of nitrogen fixation, and thus is a prelude to symbiosis. Although some of the early nodulin genes are induced prior to or during infection, induction of late nodulins requires endocytotic release of bacteria.

Plant Cell Responses to Arbuscular Mycorrhizal Fungi: Getting to the Roots of the Symbiosis

“…lnduced polypeptides are most frequent and can represent -4% of resolved polypeptides (DumasGaudot et al, 1994b;Samra et al, 1996). Although such mycorrhiza-induced polypeptides have been called mycorrhizins, in analogy to nodulins, actinorhizins, and haustorins in other plant-microbe interactions (verma et al, 1992;Roberts et al, 1993;Seguin and Lalonde, 1993), those of plant origin have not been conclusively identified. Mycorrhiza-resistant pea mutants respond differently when challenged with an AM fungus, the major modification being the disappearance of polypeptides normally present in uninoculated plants (Samra et al, 1996).…”

Developmental biology of legume nodulation

“…Most of the late nodulins are expressed at the same time or slightly after the induction of the Lb genes (see references in Verma et al, 1992).…”

Soluble and membrane symbiosis‐related polypeptides associated with the development of arbuscular mycorrhizas in tomato (Lycopersicon esculentum)

“…These studies have shown that mycorrhizal colonization of the root system results in the appearance of new proteins, increases the production of some polypeptides already present in uninfected roots and\or decreases the amount of others. The newly induced polypeptides, of plant or fungal origin, have been called endomycorrhizins by analogy to nodulins (Verma, Hu & Zhang, 1992), ectomycorrhizins (Hilbert & Martin, 1988), and haustorins (Roberts et al, 1993), produced in other plant-microbe interactions. However, the origin and role of these endomycorrhizins have not yet been determined, although some of them could be similar to certain nodulins induced during the Rhizobium-legume symbiosis (van Rhijn et al, 1997).…”