Switch from intracellular to intercellular invasion during water stress-tolerant legume nodulation
- *Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, Technologiepark 927, B-9052 Gent, Belgium; and †Centre for High Resolution Imaging and Processing, School of Life Sciences, University of Dundee, Nethergate, Dundee DD1 4HN, United Kingdom
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Communicated by Patricia C. Zambryski, University of California, Berkeley, CA, March 4, 2004 (received for review December 12, 2003)
Abstract
Rhizobia colonize their legume hosts by different modes of entry while initiating symbiotic nitrogen fixation. Most legumes are invaded via growing root hairs by the root hair-curl mechanism, which involves epidermal cell responses. However, invasion of a number of tropical legumes happens through fissures at lateral root bases by cortical, intercellular crack entry. In the semiaquatic Sesbania rostrata, the bacteria entered via root hair curls under nonflooding conditions. Upon flooding, root hair growth was prevented, invasion on accessible root hairs was inhibited, and intercellular invasion was recruited. The plant hormone ethylene was involved in these processes. The occurrence of both invasion pathways on the same host plant enabled a comparison to be made of the structural requirements for the perception of nodulation factors, which were more stringent for the epidermal root hair invasion than for the cortical intercellular invasion at lateral root bases.
Footnotes
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↵ ‡ To whom correspondence should be addressed. E-mail: marcelle.holsters{at}psb.ugent.be.
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Abbreviations: ACC, 1-aminocyclopropane-1-carboxylate; AVG, l-α-(2-aminoethoxyvinyl)-glycine; DPI, days postinoculation; GUS, β-glucuronidase; Nod factor, nodulation factor.
- Copyright © 2004, The National Academy of Sciences
