NIN-like Proteins: Key Regulators of Plant Responses to Nitrogen Availability

Nitrogen is an essential macroelement for plant growth. Nitrate, beside its role as nutrient, acts as a signal molecule for triggering many adaptive responses to changes in N availability. How such nitrate specific mechanisms are regulated at the molecular level is poorly understood. We identified NIN-like protein 7 (NLP7), a member of the RWP-RK family of putative transcription factors, as an important element involved in the adaptation to N availability. Nlp7 knockout mutants constitutively display several traits of nitrogen starved plants and NLP7 expression pattern is consistent with a function in the sensing of N and translational fusions with the green fluorescent protein (GFP) show a nuclear localization for NLP7. Indeed, immediately after nitrate exposure, NLP7 accumulates in the nucleus and binds dozens of genes involved in nitrate signalling and assimilation leading to an altered response of many nitrate-regulated genes in the nlp7 mutant background. Altogether, we propose NLP7 as a master regulator of early nitrate signalling.