Transcriptome Profiling of Developing Internode Submitted to Different Water Regimes in Sorghum: Insights in the Regulation of Biomass Accumulation and Composition

Sorghum bicolor, a cereal native of Africa, is currently used for both feed and food. According to its biomass yield potentials and its biochemical composition variability it is also envisioned as a relevant species to support biomass value chains (energy, biomaterials). In this context, in order to adapt sorghum varieties to the different end-uses, it is of paramount importance to understand the regulation of biomass establishment (yield and biochemical composition) in the stem all over the plant development cycle.

The objectives of this study were to i) describe the evolution of the sorghum stem composition along its development in contrasting water regimes and ii) follow up the transcriptome regulation underlying this evolution. In this context, two internode levels were analysed over two consecutive years at different developmental stages under two watering regimes (Well watered vs Water Deficit) for one commercial biomass hybrid. At the biochemical level, apart from the classical evolutions already described regarding sucrose and the cell wall components (lignin, cellulose, hemicellulose) during internode development, a strong impact of the water regimes on the different biomass components were observed (lignin reduction and sucrose accumulation in the internode in the Water deficit treatment). RNA seq analyses over the different internodes levels, stages and water regimes provided insights in the understanding of biomass composition evolution. A more detailed analysis was performed on the lignin biosynthesis pathway in order to identify the key regulators involved in the accumulation of this key trait.