| Abstract Detail
Plant-Symbiont Interactions Mukherjee, Arijit [1], Smith, Lucinda [2], Schnabel, Elise [1], Long, Sharon [2], Frugoli, Julia [1]. The lss supernodulation mutant in Medicago truncatula. The beneficial symbiotic association between host legume plants and compatible nitrogen fixing rhizobia culminates in the formation of root nodules. Legumes control the extent of root nodule formation through a regulatory mechanism in which nodulating roots induce a shoot response that signals back to the roots, inhibiting further nodule initiation and development. Disruption of genes involved in this regulatory process leads to super or hypernodulation. The lss (like sunn supernodulator) mutant of Medicago truncatula was identified as a naturally occurring supernodulation mutation in the Jemalong cultivar. The phenotype of lss is practically indistinguishable from the phenotype of sunn with respect to both root length and nodule number. The sunn mutant is a previously characterized supernodulator resulting from mutations in a LRR-receptor kinase. Shoot grafting experiments show that supernodulation in lss is a shoot-controlled phenotype, as in sunn, however lss and sunn plants nodulate differently in the presence of nitrogen, and SUNN gene expression is altered in lss mutant shoots versus sunn mutant shoots. Interestingly, F1 analysis of progeny from lss crossed with sunn demonstrated that the two mutations do not complement each other and the nodule and root phenotypes of the F1 are indistinguishable from either sunn or lss under the conditions we are using for nodulation and growth. Sequencing of the SUNN gene in lss plants revealed no lesion in SUNN, and we can find no lesion in the promoter sequence or 530 bases past the poly A site. Inspection of F2 plants from the lss/sunn cross revealed plants with a wild-type level of nodulation in a ratio suggesting separate but linked genes, confirmed from mapping of the gene through a separate cross to the polymorphic ecotype A20. Analysis of segregating CAPS markers in the F2 from this cross determined that lss maps to an 800 kB area at the bottom of LG4 which also contains sunn. We are currently exploring the possibility that lss is an epigenetic allele of SUNN gene or a potential cis acting factor for the SUNN promoter.
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1 - Clemson University, Department of Genetics and Biochemistry
2 - Stanford University, Department of Biological Sciences
Keywords:
nodulation
autoregulation of nodulation
lss
SUNN.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P16022
Abstract ID:2670 |
