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International Journal of Agronomy
Volume 2016, Article ID 1369472, 9 pages
http://dx.doi.org/10.1155/2016/1369472
Review Article

The Role of Rhizobial ACC Deaminase in the Nodulation Process of Leguminous Plants

1Laboratório de Bioprocessos, Departamento de Microbiologia, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, SC, Brazil
2Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM) (Laboratório de Microbiologia do Solo), Universidade de Évora, Núcleo da Mitra, 7000-083 Évora, Portugal
3Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, 7000-083 Évora, Portugal
4Department of Biology, University of Waterloo, Waterloo, ON, Canada N2L 3G1

Received 27 November 2015; Accepted 28 April 2016

Academic Editor: Othmane Merah

Copyright © 2016 Francisco X. Nascimento et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Symbiotic rhizobia-legumes associations are extremely important in terms of sustainable agricultural practices. This symbiosis involves a complex interaction between both partners, plant and bacterium, for bacterial infection and the formation of symbiotic N-fixing nodules. In this regard, the phytohormone ethylene plays a significant role in nodule formation, acting as an inhibitor of the nodulation process. Ethylene not only regulates nodule development but also regulates many other plant developmental cues, including various stress responses that inhibit overall plant growth. Some rhizobia produce the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, thus, being able to decrease ACC and, consequently, decrease deleterious ethylene levels that affect the nodulation process. This occurs because ACC is the immediate precursor of ethylene in all higher plants. Hence, rhizobia that express this enzyme have an increased symbiotic potential. In addition to the direct role that ACC deaminase plays in the nodulation process per se, in a limited number of instances, ACC deaminase can also modulate nodule persistence. This review focuses on the important role of rhizobial ACC deaminase during the nodulation process, emphasizing its significance to legume growth promotion.