Résumé
Nitrogen (N) is an essential macronutrient for plant growth. Plants primarily take up N from the soil in the form of nitrate (NO3-) and ammonium (NH4+). Ammonium fertilization can serve to mitigate the negative environmental effects associated with NO3- application in agriculture. However, ammonium nutrition can lead to stress occurrence, the main symptom of ammonium stress being a reduction in growth. As every nutrient, N does not act isolated on plant physiology but acts in coordination with other nutrients. In this regard, recent studies highlighted the importance of the connection between iron (Fe) homeostasis and NH4+ metabolism for plant performance. For instance, our research group has described increased phytosiderophore synthesis and Fe uptake in the root of Brachypodium distachyon when grown with NH4+ as source of N (De la Peña et al., 2022). Furthermore, Fe supply has been found as a key aspect that can determine ammonium tolerance in Arabidopsis, (Coleto et al., 2021). In addition, the coordination between Fe and sulfur (S) is well known. For example, ammonium nutrition increased S assimilation in oilseed rape (Coleto et al., 2017). In this context, we hypothesized that the interplay between Fe and S homeostasis may be a key aspect for plant development under ammonium nutrition. Thus, the aim of our work is to further understand this triple nutritional interaction in monocots (B. distachyon and wheat). To do so, on one hand we took profit of a natural variation study regarding ammonium tolerance performed with 52 B. distachyon accessions (De La Peña et al., submitted), and selected two ammonium- sensitive and two –tolerant accessions to evaluate whether their performance under ammonium nutrition is related to Fe homeostasis. On the other hand, we studied the physiological and transcriptomic response of wheat (Triticum aestivum var. cezanne) grown with NO3- or NH4+ as source of N when subjected Fe and S deficiency. By analyzing co-expression and gene regulatory network analysis, we identified several transcription factors that may have a relevant role in this interaction, and thus, be important to improve crop performance under ammonium nutrition.ReferencesColeto I. et al. (2017) Leaves play a central role in the adaptation of nitrogen and sulfur metabolism to ammonium nutrition in oilseed rape (Brassica napus). BMC Plant Biol., 17: 157Coleto I. et al. (2021) Arabidopsis thaliana transcription factors MYB28 and MYB29 shape ammonium stress responses by regulating Fe homeostasis. New Phytol. 229: 1021-1035De la Peña M. et al. (2022) Ammonium nutrition interacts with iron homeostasis in Brachypodium distachyon. J. Exp. Bot.73: 263-274 De la Peña M. et al. (2024) The metabolic adaptation determines the natural variation in ammonium tolerance in the model grass Brachypodium distachyon. Under reviewFunding Acknowledgement:This work was supported by the Consolidated Groups programme (IT1560-22) of the Basque Government and by MICIN/AEI/10.13039/501100011033 (project PID2020-113385RBI00) co-funded by ‘ERDF A way of making Europe’. LU benefited from a PhD grant from the Basque Government. The authors also thank SGIker (UPV/EHU, ERDF, UE) for the technical and human support provided.