The NAC transcription factor LuNAC61 negatively regulates fiber development in flax (Linum usitatissimum L.)

Abstract

Flax is a crucial fiber crop that exhibits excellent textile properties and serves as a model plant for investigating phloem fiber development. The regulation of multiple genes significantly influences fiber development, notably involving NAC (NAM, ATAF1/2, CUC2) transcription factors in forming the fiber secondary cell wall (SCW). Overexpression of LuNAC61 in flax resulted in sparse top meristematic zone leaves and significantly reduced stem cellulose content. Scanning electron microscopy and staining observations revealed a significant reduction in fiber bundles. β-Glucuronidase (GUS) staining analysis demonstrated high activity of the LuNAC61 promoter in the bast fibers of the flax stem. Additionally, several members of the LuPLATZ and LuCesA families exhibited significant coexpression with LuNAC61. Subcellular localization indicated the presence of LuPLATZ24 protein in the nucleus and cytoplasm, LuNAC61 protein exclusively in the nucleus, and LuCesA10 in the nucleus and endoplasmic reticulum. LuPLATZ24 positively regulates LuNAC61, whereas LuNAC61 negatively affects LuCesA10, suggesting the involvement of a metabolic network in regulating flax fiber development. In conclusion, this study provides a critical opportunity for a comprehensive and in-depth analysis of the mechanisms governing flax fiber development and the potential use of biotechnology to enhance flax fiber yield.