Dual Genetic Pathways Controlling Nodule Number in Medicago truncatula1
We report the isolation and characterization of a new Medicago truncatula hyper-nodulation mutant, designated sunn (super numeric nodules). Similar to the previously described ethylene-insensitive mutant sickle , sunn exhibits a 10-fold increase in the number of nodules within the primary nodulation...
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Veröffentlicht in: | Plant physiology (Bethesda) 2003-03, Vol.131 (3), p.998-1008 |
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Hauptverfasser: | , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | We report the isolation and characterization of a new
Medicago truncatula
hyper-nodulation mutant, designated
sunn
(super numeric nodules). Similar to the previously described ethylene-insensitive mutant
sickle
,
sunn
exhibits a 10-fold increase in the number of nodules within the primary nodulation zone. Despite this general similarity, these two mutants are readily distinguished based on anatomical, genetic, physiological, and molecular criteria. In contrast to
sickle
, where insensitivity to ethylene is thought to be causal to the hyper-nodulation phenotype (R.V. Penmetsa, D.R. Cook [1997] Science 275: 527–530), nodulation in
sunn
is normally sensitive to ethylene. Nevertheless,
sunn
exhibits seedling root growth that is insensitive to ethylene, although other aspects of the ethylene triple response are normal; these observations suggest that hormonal responses might condition the
sunn
phenotype in a manner distinct from
sickle
. The two mutants also differ in the anatomy of the nodulation zone: Successful infection and nodule development in
sunn
occur predominantly opposite xylem poles, similar to wild type. In
sickle
, however, both infection and nodulation occur randomly throughout the circumference of the developing root. Genetic analysis indicates that
sunn
and
sickle
correspond to separate and unlinked loci, whereas the
sunn/skl
double mutant exhibits a novel and additive super-nodulation phenotype. Taken together, these results suggest a working hypothesis wherein
sunn
and
sickle
define distinct genetic pathways, with
skl
regulating the number and distribution of successful infection events, and
sunn
regulating nodule organogenesis. |
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ISSN: | 0032-0889 1532-2548 |
DOI: | 10.1104/pp.015677 |