A nod factor binding lectin with apyrase activity from legume roots

Abstract

A lectin isolated from the roots of the legume, Dolichos biflorus, binds to Nod factors produced by rhizobial strains that nodulate this plant and has a deduced amino acid sequence with no significant homology to any lectin reported to date. This lectin also is an enzyme that catalyzes the hydrolysis of phosphoanhydride bonds of nucleoside di-and triphosphates; the enzyme activity is increased in the presence of carbohydrate ligands. This lectin-nucleotide phosphohydrolase (LNP) has a substrate specificity characteristic of the apyrase category of phosphohydrolases, and its sequence contains four motifs characteristic of this category of enzymes. LNP is present on the surface of the root hairs, and treatment of roots with antiserum to LNP inhibits their ability to undergo root hair deformation and to form nodules on exposure to rhizobia. These properties suggest that this protein may play a role in the rhizobium-legume symbiosis and/or in a related carbohydrate recognition event endogenous to the plant.Oligosaccharide signaling events play important roles in the regulation of plant development, defense, and other interactions of plants with the environment (1-4). The establishment of the nitrogen-fixing symbiotic relationship between rhizobia and leguminous plants depends on such a signaling process. The rhizobia produce lipochitooligosaccharidic signals, called Nod factors, that elicit the differentiation of a new organ, the nodule, in the root cortex. The rhizobia bind to and invade the root hairs, where they proceed to the emerging nodule within infection threads produced by the plant (5). Both the initiation of nodule formation and rhizobial entry are host-strainspecific; this specificity is determined by the type of Nod factor produced by a particular rhizobial strain and by the ability of a leguminous species to recognize that signal.All Nod factors consist of a short, typically tetrapentameric, chitin oligosaccharidic backbone that is N-acylated at the nonreducing end, usually with a common fatty acid, such as cis-vaccenic acid. The Nod factors differ from one another in length of this backbone and the type of substituents that decorate it; these modifications determine the strain specificity of the rhizobium and depend on the set of nodulation genes possessed by that rhizobial strain (4). A related set of signals are the chitin oligosaccharides, themselves, that have been found to elicit defense responses in a wide variety of plants (for review, see ref.3).Although the structures of many of these chitooligosaccharides have been characterized, little is known about the plant proteins that bind these signals, whether as receptors for signal transduction or as binding proteins with other functions. High-affinity binding sites for chitin fragments have been found on membranous fractions prepared from tomato (7) and rice (8) suspension-cultured cells, and a 70-kDa protein that binds to chitin fragments was isolated from the rice membranes (9). Particulate fractions from roots of the legume, Medicago t...

Purification and Biochemical Characterization of a Novel Ecto-Apyrase, MP67, from Mimosa pudica

“…Differential expression of apyrase isoforms has been previously reported. In particular, legume-specific apyrases are highly expressed in roots (Etzler et al, 1999;Day et al, 2000). MP67 expression in seedlings was at the trace level; consistently, ADPase activity was mainly detected in the leaves of grown plants.…”

“…The expression of MP67 was higher than that of MpAPY2, telling us that MP67 plays a role distinct from conventional apyrase. The legume-specific apyrases such as DbLNP (Etzler et al, 1999) from D. biflorus and GS52 (Day et al, 2000;Kalsi and Etzler, 2000) from G. soja are localized to the cell membrane and are known to function in the nodulation of legumes. Potato (Solanum tuberosum)-specific apyrase has a signal sequence and is apoplastically localized in tissues (Riewe et al, 2008).…”

“…Accumulating evidence suggests that animal apyrases participate in several physiological events, such as neurotransmission (Sarkis and Salto, 1991), thromboregulation (Marcus et al, 1997), and protein glycosylation (Abeijon et al, 1993;Gao et al, 1999). In plants, the legume-specific apyrase DbLNP from Dolichos biflorus contributes to root nodulation; it localizes to the cell membrane and binds Nod factors produced by rhizobia, playing a role in Rhizobium-legume symbiosis (Etzler et al, 1999). GS52, an apyrase of Glycine soja, is overexpressed in Lotus japonicus, resulting in the enhancement of nodulation of the transgenic plant (McAlvin and Stacey, 2005).…”

Localization of a Nod Factor-Binding Protein in Legume Roots and Factors Influencing Its Distribution and Expression

“…It should be noted, however, that the identical electrophoretic mobilities of the Db-LNP obtained from each site suggest that the Db-LNP is undergoing identical modifications in each cell type. These modifications include the removal of a signal peptide and a 19-amino acid segment immediately downstream of this signal as well as glycosylation at at least one of two consensus N-glycosylation sites (Quinn and Etzler, 1987;Etzler et al, 1999). It should also be pointed out that the antiserum used in this investigation does not react with a second, related nucleotide phosphohydrolase found in legumes as well as in other families of plants .…”

Purification and cDNA cloning of a lectin and a lectin-like protein from Apios americana Medikus tubers

“…5) A few legume lectins have been purified from leaves 7) and roots, 8,9) but most have been identified and purified from the seeds.…”