In order to identify plant genes involved in the Rhizobium/legume root nodule symbiosis, host gene expression during soybean nodule development was studied. The hybridization of complementary DNA (cDNA) probes with homologous and heterologous polyadenylated polysomal RNAs showed that most of the 20,000-25,000 RNA sequences expressed were common to uninfected root and nodule tissues. There was a marked increase in the relative concentration of leghaemoglobin and moderately abundant nodule sequences following infection by Rhizobium. A nodule-specific cDNA probe (NS-cDNA), prepared by eliminating common root sequences by cascade hydroxylapatite chromatography, was used to characterize a small population of nodule-specific sequences. Hybridization of NS-cDNA to DNA from soybean embryos and not to Rhizobium demonstrated that these sequences are encoded by the host genome. Hybridization with nuclear RNA from uninfected tissues showed that the primary mode of regulation of these sequences is at the level of transcription. Expression of these small nodule-specific-mRNAs is differentially modulated by ineffective strains of Rhizobium. The relative concentration of nodule-specific and common moderately abundant sequences increased to varying extents, in parallel with leghaemoglobin, reaching a peak when nitrogen fixation commences. These data suggest that host gene expression is coordinately regulated during early nodule development. Indoleacetic acid appeared to modulate the expression of common moderately abundance sequences, but had no detectable effect upon leghaemoglobin or nodule-specific sequences. Preliminary characterization of 26 cDNA clones indicated that, in addition to leghaemoglobin and other positively regulated sequences, there were two clones whose mRNA concentration decreased during nodule development.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.68600 |
| Date | January 1981 |
| Creators | Auger, Sandra Goodman. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000139119, proquestno: AAINK54737, Theses scanned by UMI/ProQuest. |
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