LOCAL AND LONG-RANGE SIGNALING PATHWAYS REGULATING PLANT RESPONSES TO NITRATE

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Abstract
▪ Abstract Nitrate is the major source of nitrogen (N) for plants growing in aerobic soils. However, the NO3− ion is also used by plants as a signal to reprogram plant metabolism and to trigger changes in plant architecture. A striking example is the way that a root system can react to a localized source of NO3− by activating the NO3− uptake system and proliferating lateral roots preferentially within the NO3−-rich zone. That roots are able to respond autonomously in this fashion implies the existence of local signaling pathways that are sensitive to local changes in the external NO3− concentration. On the other hand, long-range signaling pathways are also needed to modulate these responses according to the plant's N status and to coordinate the allocation of resources between the root and the shoot. This review examines these signaling mechanisms and their interactions with sugar-sensing and hormonal response pathways.