BUSCADOR RECOLECTA

Background: The coordination between nitrogen (N) and sulfur (S) assimilation is required to suitably provide
plants with organic compounds essential for their development and growth. The N source induces the adaptation
of many metabolic processes in plants; however, there is scarce information about the influence that it may exert
on the functioning of S metabolism. The aim of this work was to provide an overview of N and S metabolism in
oilseed rape (Brassica napus) when exposed to different N sources. To do so, plants were grown in hydroponic
conditions with nitrate or ammonium as N source at two concentrations (0.5 and 1 mM).
Results: Metabolic changes mainly occurred in leaves, where ammonium caused the up-regulation of enzymes
involved in the primary assimilation of N and a general increase in the concentration of N-compounds (NH4
+, amino
acids and proteins). Similarly, the activity of key enzymes of primary S assimilation and the content of S-compounds
(glutathione and glucosinolates) were also higher in leaves of ammonium-fed plants. Interestingly, sulfate level was
lower in leaves of ammonium-fed plants, which was accompanied by the down-regulation of SULTR1 transporters
gene expression.
Conclusions: The results highlight the impact of the N source on different steps of N and S metabolism in oilseed
rape, notably inducing N and S assimilation in leaves, and put forward the potential of N source management to
modulate the synthesis of compounds with biotechnological interest, such as glucosinolates., The design of the study, analysis and interpretation of data and writing of
the manuscript was supported by the Basque Government [IT932–16], the
Spanish Ministry of Economy and Competitiveness [AGL2015–68881-REDT]
and [BIO2014–56271-R] co-funded by FEDER and the People Programme
(Marie Curie Actions) of the European Union’s Seventh Framework
Programme (FP7/2007–2013) under REA grant agreement number 334019.

Accessing different nitrogen (N) sources involves a profound adaptation of plant metabolism. In this study, a quantitative proteomic approach was used to further understand how the model plant Arabidopsis thaliana adjusts to different N sources when grown exclusively under nitrate or ammonium nutrition. Proteome data evidenced that glucosinolate metabolism was differentially regulated by the N source and that both TGG1 and TGG2 myrosinases were more abundant under ammonium nutrition, which is generally considered to be a stressful situation. Moreover, Arabidopsis plants displayed glucosinolate accumulation and induced myrosinase activity under ammonium nutrition. Interestingly, these results were also confirmed in the economically important crop broccoli (Brassica oleracea var. italica). Moreover, these metabolic changes were correlated in Arabidopsis with the differential expression of genes from the aliphatic glucosinolate metabolic pathway. This study underlines the importance of nitrogen nutrition and the potential of using ammonium as the N source in order to stimulate glucosinolate metabolism, which may have important applications not only in terms of reducing pesticide use, but also for increasing plants’ nutritional value., This research was financially supported by the Basque Government (IT932-16), the Spanish Ministry of Economy and Competitiveness (AGL2015-64582-C3-1-R and BIO2014-56271-R co-funded by FEDER), and the
People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007–2013) under REA grant agreement number 334019. Navarrabiomed Proteomics Unit is a member of ProteoRed, PRB2-ISCIII, and is supported by grant PT13/0001, of the PE I+D+I 2013-2016 funded by ISCIII and FEDER.