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

Abstract

The roots of the legume Dolichos biflorus contain a lectin/nucleotide phosphohydrolase (Db-LNP) that binds to the Nod factor signals produced by rhizobia that nodulate this plant. In this study we show that Db-LNP is differentially distributed along the surface of the root axis in a pattern that correlates with the zone of nodulation of the root. Db-LNP is present on the surface of young and emerging root hairs and redistributes to the tips of the root hairs in response to treatment of the roots with a rhizobial symbiont or with a carbohydrate ligand. This redistribution does not occur in response to a non-symbiotic rhizobial strain or a root pathogen. Db-LNP is also present in the root pericycle where its level decreases upon initiation of nodule formation. Maximum levels of Db-LNP are found in 2-d-old roots, and the expression of this root protein is increased when the plants are grown in the absence of NO 3 Ϫ and NH 4 ϩ . These results support the possibility that Db-LNP is involved in the initiation of the Rhizobium legume symbiosis.

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

“…In most legumes, two types of apyrase are present; a legume-specific APY1-type apyrase and an APY2-type apyrase. Apyrases of the legume-specific type, such as DbLNP and GS52, are known to function in Rhizobiumlegume symbiosis (Day et al, 2000;Kalsi and Etzler, 2000;McAlvin and Stacey, 2005;Govindarajulu et al, 2009). In this study, no cDNA clone belonging to the legume-specific apyrase family was obtained.…”

“…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).…”

Rhizobial and Mycorrhizal Symbioses in Lotus japonicus Require Lectin Nucleotide Phosphohydrolase, Which Acts Upstream of Calcium Signaling

“…The localization of LNP to legume root hair cells, its rhizobiainduced accumulation at root hair tips, the ability of LNP antiserum to interfere with nodulation Kalsi and Etzler, 2000), and the finding that silencing LNP in soybean reduces nodulation (Govindarajulu et al, 2009) all pointed to a function for LNP in nodulation signaling. In this work, we inhibited the formation of LNP and revealed that in three independent antisense lines, there was no nodulation following inoculation with M. loti.…”

“…LNP can be detected around the surface of root hairs using immunofluorescence (Kalsi and Etzler, 2000;Fig. 1E).…”

“…In mammalian systems, such enzymatic activity was proposed to remove extracellular ATP, known to be toxic to cells. This LECTIN NU-CLEOTIDE PHOSPHOHYDROLASE (LNP) is a peripheral membrane protein present on the surface of epidermal root hairs in the zone of the root with the capacity to nodulate and is redistributed to the tips of the root hairs upon exposure to rhizobia or Nod factors (Kalsi and Etzler, 2000). The importance of LNP for the establishment of the rhizobial symbiosis was indicated following pretreatment of the roots with antiserum against recombinant LNP that inhibited both root hair deformation and nodulation in response to rhizobia Day et al, 2000).…”