In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 97, No. 24 ( 2000-11-21), p. 13407-13412
Abstract:
The symbiotic interaction between Medicago
truncatula and Sinorhizobium meliloti results in
the formation of nitrogen-fixing nodules on the roots of the host plant. The early stages of nodule formation are induced by bacteria via
lipochitooligosaccharide signals known as Nod factors (NFs). These NFs are structurally specific for bacterium–host pairs and are sufficient
to cause a range of early responses involved in the host developmental program. Early events in the signal transduction of NFs are not well defined. We have previously reported that Medicago
sativa root hairs exposed to NF display sharp oscillations of
cytoplasmic calcium ion concentration (calcium spiking). To assess the possible role of calcium spiking in the nodulation response, we
analyzed M. truncatula mutants in five complementation
groups. Each of the plant mutants is completely Nod− and is blocked at early stages of the symbiosis. We defined two genes, DMI1 and DMI2 , required in common for
early steps of infection and nodulation and for calcium spiking. Another mutant, altered in the DMI3 gene, has a similar
mutant phenotype to dmi1 and dmi2 mutants
but displays normal calcium spiking. The calcium behavior thus implies that the DMI3 gene acts either downstream of calcium
spiking or downstream of a common branch point for the calcium response and the later nodulation responses. Two additional mutants, altered in
the NSP and HCL genes, which show root
hair branching in response to NF, are normal for calcium spiking. This system provides an opportunity to use genetics to study
ligand-stimulated calcium spiking as a signal transduction event.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.230439797
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2000
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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