Studying early nodulin gene ENOD40 expression and induction by nodulation factor and cytokinin in transgenic alfalfa.
ENOD40, an early nodulin gene, is expressed following inoculation with Rhizobium meliloti or by adding R. meliloti-produced nodulation (Nod) factors or the plant hormone cytokinin to uninoculated roots. We isolated two MsENOD40 clones, designated MsENOD40-1 and MsENOD40-2, with distinct promoters from an alfalfa (Medicago sativa cv Chief) genomic library. The promoters were fused to the reporter gene uidA (gus), and the constructs were introduced into alfalfa. We observed that the MsENOD40-1 construct was expressed almost exclusively under symbiotic conditions. The MsENOD40-2 construct was transcribed under both symbiotic and nonsymbiotic conditions and in nonnodular and nodular tissues. Both MsENOD40 promoter-gus constructs were similarly expressed as nodules developed, and both were expressed in roots treated with 6-benzylaminopurine or purified Nod factor. However, no blue color was detected in nodule-like structures induced by the auxin transport inhibitor N-1-(naphthyl)phthalamic acid on roots of plants containing the MsENOD40-1 promoter construct, whereas pseudonodules from plants containing the MsENOD40-2 promoter construct stained blue. A 616-bp region at the distal 5' end of the promoter is important for proper spatial expression of MsENOD40 in nodules and also for Nod-factor and cytokinin-induced expression.
Fang
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Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles 90095-1606, USA.
Hirsch
A M
AM
D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D003583:Cytokinins / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D017930:Genes, Reporter; D015698:Genomic Library; D000455:Medicago sativa / Q000235:genetics / Q000382:microbiology / Q000502:physiology*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D016962:Sinorhizobium meliloti / Q000502:physiology; D013559:Symbiosis
D001426:Bacterial Proteins; D003583:Cytokinins; C405430:ENOD40 RNA; D010940:Plant Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D011993:Recombinant Fusion Proteins