The NAC transcription factor OsSWN1 regulates secondary cell wall development in Oryza sativa

Rice, as a major crop in the world, produces huge agronomic biomass residues besides food, which consist of cellulose, hemicelluloses and lignin. Many master regulators of secondary wall synthesis were identified in the model plant Arabidopsis. In this study, we investigated the function of a NAC (NAM, ATAF, and CUC2) transcription factor related to secondary cell wall biosynthesis, which is highly expressed in rice sclerenchyma tissue and is named OsSWN1. Our results showed that engineering of OsSWN1 could exhibit multiple features regulated to agronomic traits and bioenergy research. Over-expression of OsSWN1 caused an erect-leaf and enclosed-flower phenotype. Secondary cell wall-related genes were actively expressed in transgenic plants with obvious ectopic lignin deposition in the leaf collar, while increased lignin content and decreased the sugar yield correspondingly. In addition, down-regulation of OsSWN1 expression levels decreased lignin content and increased the sugar yield in transgenic plants. Bioinformatics analysis revealed that OsSWN1-like genes are highly conserved in switchgrass and sorghum, suggesting a possibility of manipulating the expression level of the OsSWN1 orthologs in the bioenergy crops for biofuel production.