The SsSND1 transcription factor co-regulates cellulose and lignin biosynthesis during the formation of secondary walls in sugarcane (Saccharum spontaneum).

Sugarcane is a globally important crop for producing sugar and lignocellulosic biomass. Hemicelluloses, cellulose, and lignin are key secondary cell walls (SCWs) components, offering valuable polysaccharides and polymers. While significant research has been conducted on SCW transcription regulation, our understanding in sugarcane remains limited. Using domain searching and co-expression analysis, this study identified that SsSND1, a NAC-domain transcription factor in sugarcane ( Saccharum spontaneum ), shares high sequence similarity with its homologs AtSND1 in Arabidopsis and OsSWN1 in rice. The ectopic expression of SsSND1 in Arabidopsis showed both increased levels of lignin and cellulose. The typical SCW cellulose biosynthesis genes ( AtCESA4 , AtCESA7 , and AtCESA8 ), along with the lignin monomer biosynthesis genes ( At4CL , AtPLA4 , and AtCCoAOMT ), were significantly upregulated in the OE lines compared to the WT and mutants. SsSND1 can directly induce those genes through binding to SNBE motifs within their promoters. SsSND1 directly activates SsMYB46 , SsCESA4 , SsCESA7 , and SsCESA9 by binding to the SNBE motifs in their promoters. SsSND1 is a key positive regulator of secondary cell wall cellulose and lignin metabolism.