The impact of salinity on the symbiosis between Casuarina glauca Sieb. ex Spreng. and N2-fixing Frankia bacteria based on the analysis of Nitrogen and Carbon metabolism

Nuno Duro, Paula Batista-Santos, Mário da Costa, Rodrigo Maia, Isabel V. Castro, Margarida Ramos, José C. Ramalho, Katharina Pawlowski, Cristina Máguas, Ana Ribeiro-Barros

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Background and aims: Casuarina glauca is an actinorhizal plant that establishes root-nodule symbiosis with N2-fixing bacteria of the genus Frankia. This plant is highly recalcitrant to extreme environmental conditions such as salinity and drought. The aim of this study was to evaluate the impact of salt stress on the symbiotic relationship between C. glauca and Frankia Thr, focusing on N and C metabolism. Methods: Symbiotic and non-symbiotic plants were exposed to 0, 200, 400 and 600 mM NaCl. The following analyses were performed: stable carbon (δ13C) and nitrogen (δ15N) isotope signature; nitrogenase activity in nodules (acetylene reduction assay); and gene expression of a set of genes involved in nodule infection and N/C metabolism (qRT-PCR). Data were analysed using two-way ANOVA. Results: Salt stress induced an enrichment in δ13C and δ15N, reflecting a negative impact of salt in the relative water content and N2 fixation, respectively. Furthermore, nitrogenase activity in nodules was insignificant already at 200 mM NaCl, consistent with the expression patterns of nifH as well as of plant genes involved in nodule induction and metabolism. Conclusions: The ability of C. glauca to thrive under highly saline environments is not dependent on the symbiosis with Frankia.

Original languageEnglish
Pages (from-to)327-337
Number of pages11
JournalPlant and Soil
Volume398
Issue number1-2
DOIs
Publication statusPublished - 1 Jan 2016

Keywords

  • Actinorhizal nodules
  • Casuarina glauca
  • Frankia
  • Salt stress

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