Proteolysis and Nitrogen: emerging insights.

Nitrogen (N) is a core component of fertilizers used in modern agriculture to alleviate worldwide hunger. This comes however at environmental costs, through excess N run-off due to inefficient N use efficiency (NUE) by crops. A possible remedy to this problem would thus be the improvement of NUE which requires furthering our understanding on N homeostasis, sensing and uptake. Proteolytic pathways are linked to N homeostasis as they are recycling proteins which are bearing N and carbon. Emerging data though suggest extended functions for proteolytic pathways beyond the mere recycling of N and carbon. In this opinion article, we highlight roles of proteolytic pathways on non-symbiotic or symbiotic N uptake and systemic N sensing. We also take a different vantage point, suggesting roles of proteolytic pathways in N homeostasis which elude from the consensus that proteolytic pathways function in recycling.