Bnt05G007257, a Novel NAC Transcription Factor, Predicts Developmental and Synthesis Capabilities of Fiber Cells in Ramie (Boehmeria nivea L.)

Abstract

NAC transcription factors are one of the largest transcription factor families in plants, and they play a key role in the growth and development of a secondary cell wall. Despite the fact that ramie is well-known for its high fiber yield, the role of NAC transcription factors in ramie secondary cell wall synthesis and fiber development remains unknown. In this study, based on our previous study, we describe the characterization, physicochemical property analysis, protein structure and function prediction, subcellular localization, and functional validation of Bnt05G007257, which encodes an NAC transcription factor from ramie, in transgenic A. thaliana. Our findings show that the open reading frame of Bnt05G007257 was 1035 bp long and encodes for a protein comprising 344 amino acids, having a relative molecular mass of 39.0945 kDa and a theoretical isoelectric point of 6.55. The secondary structure of the encoded protein mainly consisted of random coiling, with a typical conserved structural domain of NAC. The phylogenetic tree revealed that Bnt05G007257 is a homolog of the NAC transcription factor SND2, which regulates secondary wall biosynthesis in A. thaliana. Subcellular localization showed that Bnt05G007257 was tentatively predicted to be localized in the cytoplasm. Furthermore, in stem sections, the secondary wall fiber cells’ thickness in Bnt05G007257 transgenic plants was 31.50% thicker than that in wild-type plants, and the radial width was significantly increased by approximately 21.75%. This indicates that the NAC family homolog Bnt05G007257 may have the potential function of promoting fiber cell development and secondary cell wall synthesis, providing a theoretical basis for the selection of high-fiber-yielding ramie varieties in the future.