The role of the MfSWN1 in secondary wall growth and development

Background The formation of secondary cell walls (SCWs) determines lignocellulosic composition and cell wall architecture. NAC transcription factors ( NAM / ATAF1 / CUC2 ) act as master regulators of the SCW transcriptional network. This study characterized MfSWN1 , a Miscanthus floridulus NAC transcription factor homologous to NAC regulators of SCW synthesis, using Arabidopsis thaliana as a heterologous system. Methods The wild-type (Col-0), the SCW-deficient double mutant nst1–1 nst3-1 , MfSWN1 complementation line ( MfSWN1 -OE/ nst1–1 nst3-1 ), and MfSWN1 overexpression line ( MfSWN1 -OX) were compared to profile the function of MfSWN1 . Subsequent investigations focused on assessing developmental phenotypes, the expression of SCW marker genes, stem histology, cell wall composition, and cellulose structural properties cellulose crystallinity index (CrI) and cellulose degree of polymerization (DP) in stem tissues. Results MfSWN1 complementation partially rescued stem lodging and indehiscent silique phenotypes of nst1–1 nst3-1 . Constitutive MfSWN1 overexpression resulted in enlarged and wrinkled rosette leaves, delayed bolting, curved siliques, and enhanced lignification in stem tissues. MfSWN1 -OE/ nst1–1 nst3–1 plants showed increased transcript levels of SCW-related genes ( MYB46 , MYB83 , CesA4 , IRX7 , IRX8 , CCoAOMT1 , and LAC4 ) compared with the nst1–1 nst3–1 mutant. In contrast, MfSWN1 -OX plants showed increased expression of most of these genes relative to wild-type plants. Besides, MfSWN1 -OX plants accumulated higher levels of cellulose, hemicellulose, and lignin, as well as increased CrI and DP than other genotypes. Conclusion MfSWN1 functions upstream in the NAC-MYB regulatory hierarchy, which can hasten coordinated SCW biosynthesis and modify cell wall structural organization in Arabidopsis . This study provides an evidence-based foundation for investigating MfSWN1 and related NAC regulators in Miscanthu s.