NLP7-CRF-PIN, the nitrate-cytokinin-auxin crosstalk module, conveys root nitrate signals and regulates shoot growth adaptive responses (PNAS)

Nitrate, the prominent form of nitrogen used by most land plants, is a signal regulating plant growth and development. Nitrate sensing by roots not only regulates root development to facilitate nutrient foraging, but also the growth of distant plant organs. Cytokinin is a mobile signal coordinating nitrate dependent shoot growth responses. Abualia et al. show the involvement of cytokinin signalling and polar auxin transport (PAT) in nitrate-regulated shoot growth. The early response to nitrate provision coincides with changes in PAT in seedlings, and nitrate-promoted shoot growth was attenuated in the auxin efflux transporter mutants pin4 and pin7. Shoot expression of cytokinin response factors (CRF2 and CRF6) was promoted by nitrate, while the nitrate-promoted shoot growth was attenuated in crf2 and crf7 mutants. The nitrate master sensor NIN like protein 7 (NLP7) regulates the expression of PINs and CRFs in a nitrate-dependent manner. The weakened expression of cytokinin responsive ARR5 expression in nlp7 mutant roots and the promotion of root growth of nlp7 mutants by exogenous cytokinin suggests that the role of cytokinin in nitrate signalling is downstream of NLP7. This study builds on the accumulating evidence for the contribution of PAT and cytokinins in regulating nitrate-guided shoot adaptive responses by means of the NLP7-CRF-PIN module. (Summary by Lekshmy Sathee @lekshmysnair) Proc. Natl. Acad. Sci. USA 10.1073/pnas.2122460119