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Lotus japonicus Contains Two Distinct ENOD40 Genes That Are Expressed in Symbiotic, Nonsymbiotic, and Embryonic Tissues

September 2000 , Volume 13 , Number  9
Pages  987 - 994

Emmanouil Flemetakis , 1 Nektarios Kavroulakis , 1 Nicolette E. M. Quaedvlieg , 2 Herman P. Spaink , 2 Maria Dimou , 1 Andreas Roussis , 2 and Panagiotis Katinakis 1

1Agricultural University of Athens, Department of Agricultural Biotechnology, Iera Odos 75, 118 55 Athens, Greece; 2Institute of Molecular Plant Sciences, Leiden University, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands

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Accepted 18 May 2000.

ENOD40, an early nodulin gene, has been postulated to play a significant role in legume root nodule ontogenesis. We have isolated two distinct ENOD40 genes from Lotus japonicus. The transcribed regions of the two ENOD40 genes share 65% homology, while the two promoters showed no significant homology. Both transcripts encode a putative dodecapeptide similar to that identified in other legumes forming determinate nodules. Both ENOD40 genes are coordinately expressed following inoculation of roots with Mesorhizobium loti or treatment with purified Nod factors. In the former case, mRNA accumulation could be detected up to 10 days following inoculation while in the latter case the accumulation was transient. High levels of both ENOD40 gene transcripts were found in nonsymbiotic tissues such as stems, fully developed flowers, green seed pods, and hypocotyls. A relatively lower level of both transcripts was observed in leaves, roots, and cotyledons. In situ hybridization studies revealed that, in mature nodules, transcripts of both ENOD40 genes accumulate in the nodule vascular system; additionally, in young seed pods strong signal is observed in the ovule, particularly in the phloem and epithelium, as well as in globular stage embryos.

Additional keywords: nodule organogenesis, symbiosis.

© 2000 The American Phytopathological Society