A high-affinity nitrate transporter PaNRT2.1 mediates dark septate endophyte (DSE) dependent nitrogen assimilation in sweet cherry roots

Background and aims Low nitrogen (N) soil environment is one of the main factors limiting crop yield and horticultural plant growth. Dark septate endophytes (DSEs) are co-occurring in 80% of terrestrial plants and they can promote the absorption of N. However, few data on the contribution of DSEs symbiosis to plant N acquisition and their molecular mechanisms are available. Methods The growth, N contents and expression of N related genes of Gisela 5, a sweet cherry rootstock colonized with and without DSE fungus S16, were measured under low and normal nitrate conditions. Subsequently, molecular identification and functional study of PaNRT2.1, a nitrate transporter highly responsive to S16, were conducted. Results In this study, we found that S16 promoted the growth and N uptake of Gisela 5 seedlings under low and normal nitrate conditions, and induced the expression of the nitrate transporter gene PaNRT2.1 in roots. The expression of PaNRT2.1 significantly affected the nitrate uptake of Gisela 5 roots and the symbiosis with S16 under low nitrate conditions. Transcriptome analysis showed that a receptor-like kinase gene PaCRK10 was significantly induced during S16 symbiosis and PaNRT2.1 overexpression, indicating a signal transduction between DSE colonization with nitrate uptake. Further studies showed that there was a strong interaction between PaNRT2.1 and PaCRK10. Conclusions Taken together, our results provide a deeper understanding of how DSE promoted N uptake by sweet cherry rootstock Gisela 5 and a more promising approach for improving N uptake efficiency through plant–microbe interactions.