Adaptation of Medicago truncatula to nitrogen limitation is modulated via local and systemic nodule developmental responses.
Adaptation of Medicago truncatula to local nitrogen (N) limitation was investigated to provide new insights into local and systemic N signaling. The split-root technique allowed a characterization of the local and systemic responses of NO(3)(-) or N(2)-fed plants to localized N limitation. (15)N and (13)C labeling were used to monitor plant nutrition. Plants expressing pMtENOD11-GUS and the sunn-2 hypernodulating mutant were used to unravel mechanisms involved in these responses. Unlike NO(3)(-)-fed plants, N(2)-fixing plants lacked the ability to compensate rapidly for a localized N limitation by up-regulating the N(2)-fixation activity of roots supplied elsewhere with N. However they displayed a long-term response via a growth stimulation of pre-existing nodules, and the generation of new nodules, likely through a decreased abortion rate of early nodulation events. Both these responses involve systemic signaling. The latter response is abolished in the sunn mutant, but the mutation does not prevent the first response. Local but also systemic regulatory mechanisms related to plant N status regulate de novo nodule development in Mt, and SUNN is required for this systemic regulation. By contrast, the stimulation of nodule growth triggered by systemic N signaling does not involve SUNN, indicating SUNN-independent signaling.
Jeudy
Christian
C
Unité Mixte de Recherche en Génétique et Ecophysiologie des Légumineuses, UMR INRA 102, BP 86510, F-21065 Dijon, France.
Ruffel
Sandrine
S
Freixes
Sandra
S
Tillard
Pascal
P
Santoni
Anne Lise
AL
Morel
Sylvain
S
Journet
Etienne-Pascal
EP
Duc
Gérard
G
Gojon
Alain
A
Lepetit
Marc
M
Salon
Christophe
C
D000222:Adaptation, Physiological / Q000187:drug effects*; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D046913:Medicago truncatula / Q000187:drug effects* / Q000254:growth & development*; D009154:Mutation / Q000235:genetics; D009566:Nitrates / Q000494:pharmacology; D009584:Nitrogen / Q000172:deficiency / Q000378:metabolism / Q000494:pharmacology*; D009586:Nitrogen Fixation / Q000187:drug effects; D055170:Plant Root Nodulation / Q000187:drug effects; D053204:Root Nodules, Plant / Q000187:drug effects* / Q000254:growth & development*; D013997:Time Factors
D009566:Nitrates; D002244:Carbon; D009584:Nitrogen