Journal Article

60Ma of legume nodulation. What's new? What's changing?

Janet I. Sprent

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 5, pages 1081-1084
Published in print March 2008 | ISSN: 0022-0957
Published online January 2008 | e-ISSN: 1460-2431 | DOI:
60Ma of legume nodulation. What's new? What's changing?

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Current evidence suggests that legumes evolved about 60 million years ago. Genetic material for nodulation was recruited from existing DNA, often following gene duplication. The initial process of infection probably did not involve either root hairs or infection threads. From this initial event, two branched pathways of nodule developmental processes evolved, one involving and one not involving the development of infection threads to ‘escort’ bacteria to young nodule cells. Extant legumes have a wide range of nodule structures and at least 25% of them do not have infection threads. The latter have uniform infected tissue whereas those that have infection threads have infected cells interspersed with uninfected (interstitial) cells. Each type of nodule may develop indeterminately, with an apical meristem, or show determinate growth. These nodule structures are host determined and are largely congruent with taxonomic position. In addition to variation on the plant side, the last 10 years have seen the recognition of many new types of ‘rhizobia’, bacteria that can induce nodulation and fix nitrogen. It is not yet possible to fit these into the emerging pattern of nodule evolution.

Keywords: Burkholderia; Cupriavidus; legume; nitrogen fixation; nodule; rhizobia

Journal Article.  2426 words. 

Subjects: Plant Sciences and Forestry

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