A membrane-associated NAC transcription factor regulates salt-responsive flowering via FLOWERING LOCUS T in Arabidopsis.

The plant-specific NAC (NAM, ATAF1/2, CUC2) transcription factors play regulatory roles in diverse developmental processes and stress responses. Notably, a subset of the NAC members, collectively designated NTLs, is membrane-associated, suggesting that membrane-mediated regulation would be an important molecular scheme functioning in rapid transcriptional responses to external stimuli. Here, we examined the physiological role of a salt-responsive NTL, NTL8, by molecular genetic and transgenic approaches. NTL8 is expressed as a membrane-associated, dormant form and subsequently processed into a transcriptionally active, nuclear form. Transgenic plants overproducing an active NTL8 form exhibited delayed flowering as well as reduced growth with small curled leaves. Accordingly, expression of FLOWERING LOCUS T (FT) and its downstream genes was significantly reduced in the transgenic plants. Furthermore, FT was significantly repressed by high salt. We therefore propose that NTL8 mediates salt-responsive flowering via FT in Arabidopsis.