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ENOD40 Gene Expression and Cytokinin Responses in the Nonnodulating, Nonmycorrhizal (NodMyc) Mutant, Masym3, of Melilotus alba Desr.
MedLine Citation:
PMID:  19516966     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Several nonnodulating, nonmycorrhizal (Nod(-)Myc(-)) mutants of Melilotus alba Desr. (white sweetclover) have been described. However, the details of their responses to Sinorhizobium meliloti have not been fully elucidated. We investigated rhizobial entry and colonization using Confocal Scanning Laser Microscopy on the Masym1-5 mutants and isolated an early nodulin (ENOD40) gene from wild-type M. alba. We focused on Masym3, the least responsive of the mutants to S. meliloti and VA-fungi, to determine its response to cytokinin. Cytokinin appears to be a downstream signal in the nodule developmental pathway based not only on our previous observations whereby Nod(-)Myc(-) alfalfa roots treated with cytokinin accumulated several ENOD gene transcripts, but also on recent reports showing the importance of cytokinin receptors for nodulation. Here we show that applying 10(-6) M 6-benzylaminopurine to uninoculated Masym3 roots elicited ENOD40 transcript accumulation. In addition, Masym3 root hairs inoculated with either wild-type S. meliloti or Nod(-)S. meliloti expressing the trans-zeatin synthase gene of Agrobacterium tumefaciens exhibited tip swelling, suggesting that cytokinin mediated this response. However, Masym3 root hair tips swelled following inoculation with Nod(-)S. meliloti or after mock-inoculation, a response resembling the phenotype of root hairs, after handling, of the Medicago truncatula mutant, dmi2. Mtdmi2 is Nod(-)Myc(-) due to a defect in a gene encoding a Nodule Receptor Kinase (NORK). Like Mtdmi2, the root hair swelling response appears in part to be mediated by touch because Masym3 root hairs not contacted by either bacteria or drops of water or buffer remain elongated and do not exhibit tip swelling.
Angie Lee; Michelle R Lum; Ann M Hirsch
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant signaling & behavior     Volume:  2     ISSN:  1559-2316     ISO Abbreviation:  Plant Signal Behav     Publication Date:  2007 Jan 
Date Detail:
Created Date:  2009-06-11     Completed Date:  2012-10-02     Revised Date:  2013-05-23    
Medline Journal Info:
Nlm Unique ID:  101291431     Medline TA:  Plant Signal Behav     Country:  United States    
Other Details:
Languages:  eng     Pagination:  33-42     Citation Subset:  -    
Department of Molecular, Cellular and Developmental Biology; University of California, Los Angeles; Los Angeles, California USA.
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