NAC domain transcription factors (TFs) are plant-specific transcriptional regulators, some of which play crucial roles in secondary cell wall (SCW) biosynthesis in plants. Cotton is one of the most important natural fiber producing crops, whose mature fiber SCW contains more than 90% cellulose with very small amounts of xylan and lignin, but little is known about the molecular mechanism underlying fiber SCW formation. We previously identified seven fiber preferentially expressed NAC members, GhFSN1-7. One, GhFSN1, was demonstrated to positively regulate fiber SCW thickening, but the functions ...