Effects of N, P, K and S on metabolism: new knowledge gained from multi-level analysis.

Deficiency of mineral nutrients such as nitrate, phosphate, potassium and sulphate strongly affects the type and amount of metabolites produced by crops with knock-on effects on nutritional quality of the crop, its processing properties and disease resistance. Owing to the multitude of biochemical reactions underlying metabolism and the high degree of connectivity between biochemical pathways, predicting the output of the metabolic network in response to a change in nutrient input is an enormous challenge. Recently several studies have taken a systemic approach monitoring the response of plants to withdrawal and/or re-supply of mineral nutrients at the level of transcripts, metabolites and enzyme activities. These multi-level studies have provided important new insight into how plants re-prioritise different metabolic pathways during nutrient shortage and how they integrate metabolism with growth. On the basis of the obtained information we can formulate specific hypotheses about the causal relationships between changes in individual transcripts, proteins and metabolites.