Digging into the transcriptome of a developing sorghum grain to find the culprits of protein content and low digestibility

International audience

إنجليزي. The potential of sorghum to cope with biotic and abiotic constraints could enable it to contribute toglobal food security in the context of climate change. However, the low digestibility of the grain reserveproteins (called kafirins) by gastrointestinal proteases is hampering its wider use for food and feed. Thestructure of the protein bodies in which are stored the kafirins is potentially responsible of this defect. Themolecular mechanisms underlying the development and modification of kafirin-containing protein bodiesare still largely unknown. In this context, our objective is to decipher the molecular mechanisms involvedin the regulation of the content and digestibility of sorghum grain reserve proteins. The evolution of thetranscriptome was monitored during the grain development of the Macia genotype, and supplementedby an analysis of gene co-expression networks (GCN). In parallel, the protein content of the grains andtheir in vitro digestibility were measured. Analyses of GCN allowed the identification of transcriptionfactors (TFs) potentially regulating the mechanisms of protein reserve establishment. We identified co-expression modules involving kafirin genes and genes orthologs to TFs already known in maize, rice andarabidopsis. In those modules, we also identified not yet identified TFs. In the future, we plan to evaluatethe role of these TFs by a simplified cellular overexpression system in sorghum protoplasts. We will alsoinvestigate variability of protein content and digestibility in a panel representing sorghum worldwidegenetic diversity and European commercial offer, in order to perform GWAS analyses and phenomic andgenomic predictions