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Title: The genetic and biochemical basis for nodulation of legumes by rhizobia

Soil bacteria of the genera Azorhizobium, Bradyrhizobium, and Rhizobium are collectively termed rhizobia. They share the ability to penetrate legume roots and elicit morphological responses that lead to the appearance of nodules. Bacteria within these symbiotic structures fix atmosphere nitrogen and thus are of immense ecological and agricultural significance. Although modern genetic analysis of rhizobia began less than 20 years ago, dozens of nodulation genes have now been identified, some in multiple species of rhizobia. These genetic advances have led to the discovery of a host surveillance system encoded by nodD and to the identification of Nod factor signals. These derivatives of oligochitin are synthesized by the protein products of nodABC, nodFE, NodPQ, and other nodulation genes: they provoke symbiotic responses on the part of the host and have generated immense interest in recent years. The symbiotic functions of other nodulation genes are nonetheless uncertain, and there remain significant gaps in the knowledge of several large groups of rhizobia with interesting biological properties. This review focuses on the nodulation genes of rhizobia, with particular emphasis on the concept of biological specificity of symbiosis with legume host plants. 419 refs.
Authors:
 [1]
  1. Univ. of Missouri, Columbia, MO (United States). Dept. of Plant Pathology
Publication Date:
OSTI Identifier:
227859
Resource Type:
Journal Article
Resource Relation:
Journal Name: CRC Critical Reviews in Biotechnology; Journal Volume: 16; Journal Issue: 1; Other Information: PBD: 1996
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 56 BIOLOGY AND MEDICINE, APPLIED STUDIES; LEGUMINOSAE; NITROGEN FIXATION; SOILS; NITROGEN CYCLE; NITRATES; METABOLISM; BACTERIA; GROWTH; PLANT GROWTH; AIR POLLUTION; BIOCHEMISTRY; SYMBIOSIS; REVIEWS