Transcriptional Profile of Elongating Energy Cane Internode Reveals Insights Through Vascular Bundle Lignification

Second-generation biofuel and/or biochemical industries will rely on dedicated crops for its economic sustainability. The ideal feedstock needs to produce biomass in high amounts and quality, which is directly linked to the cell wall composition. Energy cane is a high-biomass dedicated crop, selected during Saccharum breeding program to fit particular industrial needs of 2G bioethanol production. To investigate cell wall deposition and composition during biomass development, we select an elongating internode of energy cane pre-commercial hybrid. To characterize this process we divide the internode in five sections and performed a detailed RNAseq and histological cell wall analysis. The phoroglucinol stain revealed a remarkable gradient that range from cell division and protoxylem lignification to the internode maturation and complete vascular bundle lignification. This was also addressed by RNAseq analysis that revealed more 11,000 differentially expressed genes between the internode sections. Gene ontology analyses showed enriched categories in each section.  In agreement to hystochemical analysis, expression profile of the lignification genes showed the same gradient pattern with high expression in those sections with complete lignified vascular bundles. Gene expression analysis revealed promising candidates for transcriptional regulation of energy cane lignification.