Nitrate Transporter 1.1 is involved in regulating flowering time via transcriptional regulation of FLOWERING LOCUS C in Arabidopsis thaliana

Abstract Nitrate Transporter 1.1 (NRT1.1) is a nitrate transporter and sensor that modulates plant metabolism and growth. It has previously been shown that NRT1.1 is involved in the regulation of flowering time in Arabidopsis thaliana . In this study, we mainly used genetic and molecular methods to reveal the key flowering pathway that NRT1.1 may be involved in. Mutant alleles of CO and FLC , two crucial components in the flowering pathway, were introduced into the NRT1.1 defective mutant background by crossing. When the CO mutation was introduced into chl1-5 plants, the double mutant had delayed flowering time, and the CO transcription levels did not change in the chl1-5 plants. These results indicate that the CO- dependent photoperiod may be not associated with the delayed flowering shown by chl1-5 . However, FLC loss of function could rescue the late flowering phenotype of the chl1-5 mutant, and FLC expression levels significantly increased in the NRT1.1 defective mutant plants. The FT expression levels in the chl1-5flc-3 double mutant plants recovered when the FLC mutation was introduced into chl1-5 plants and the up-regulation of FLC transcripts in the chl1-5 mutant plants was not related to nitrate availability. Our findings suggest that NRT1.1 affects flowering time via interaction with the FLC -dependent flowering pathway to influence its target gene FT , and that NRT1.1 may be included in an additional signaling pathway that represses the expression of FLC in a nitrate-independent manner.