1Institut des Sciences Végétales, CNRS, Avenue de la Terrasse, F-91198 Gif sur Yvette Cedex, France; 2Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged P.O. Box 521, H-6701 Hungary
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Accepted 30 October 1996.
During development of nodules and roots, the alfalfa early nodulin gene MsEnod12A is expressed adjacent to the meristem. Using transgenic alfalfa carrying a MsEnod12A promoter-gusA fusion, we investigated the regulation of MsEnod12A expression in mature nodules and roots by GUS assays and reverse transcription-PCR. We found that in alfalfa indeterminate nodules induced by various Fix- Rhizobium meliloti mutants and in spontaneous nodules devoid of rhizobia, MsEnod12A was expressed at the distal end when a persistent meristem was present. However, this gene was not expressed when the meristem was lacking in nodules arrested in development. The MsEnod12A-gusA fusion was introduced into Lotus corniculatus plants that form determinate nodules devoid of a persistent meristem. Using these plants we found MsEnod12A-gusA expression only in young nodules and a disappearance in mature nodules. Moreover, when alfalfa roots were treated with auxins a lateral band of MsEnod12A expression was observed surrounding the club-shaped root apex and coinciding with induced lateral meristematic activities. Thus, in all cases MsEnod12A expression was associated with meristematic activities, suggesting that MsEnod12A plays a role in the differentiation processes of nodule and root cells and that it may serve as molecular tool for analyzing meristem establishment during nodule development.
gusA reporter gene.
© 1997 The American Phytopathological Society