title: Carbon metabolism and bacteroid functioning are involved in the regulation of nitrogen fixation in Medicago truncatula under drought and recovery.
abstract: Regulation of symbiotic nitrogen fixation (SNF) during drought stress is complex and not yet fully understood. In the present work, the involvement of nodule C and N metabolism in the regulation of SNF in Medicago truncatula under drought and a subsequent rewatering treatment was analyzed using a combination of metabolomic and proteomic approaches. Drought induced a reduction of SNF rates and major changes in the metabolic profile of nodules, mostly an accumulation of amino acids (Pro, His, and Trp) and carbohydrates (sucrose, galactinol, raffinose, and trehalose). This accumulation was coincidental with a decline in the levels of bacteroid proteins involved in SNF and C metabolism, along with a partial reduction of the levels of plant sucrose synthase 1 (SuSy1). In contrast, the variations in enzymes related to N assimilation were found not to correlate with the reduction in SNF, suggesting that these enzymes do not have a role in the regulation of SNF. Unlike the situation in other legumes such as pea and soybean, the drought-induced inhibition of SNF in M. truncatula appears to be caused by impairment of bacteroid metabolism and N(2)-fixing capacity rather than a limitation of respiratory substrate.
authors.affiliation: Departamento Ciencias del Medio Natural, Universidad Pública de Navarra, Pamplona, Spain.
authors.forename: Estíbaliz
authors.initials: E
authors.lastname: Larrainzar
authors.forename: Stefanie
authors.initials: S
authors.lastname: Wienkoop
authors.forename: Christian
authors.initials: C
authors.lastname: Scherling
authors.forename: Stefan
authors.initials: S
authors.lastname: Kempa
authors.forename: Rubén
authors.initials: R
authors.lastname: Ladrera
authors.forename: Cesar
authors.initials: C
authors.lastname: Arrese-Igor
authors.forename: Wolfram
authors.initials: W
authors.lastname: Weckwerth
authors.forename: Esther M
authors.initials: EM
authors.lastname: González
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D055864:Droughts; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D046913:Medicago truncatula / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D014867:Water / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D014867:Water; D002244:Carbon