Molecular networks controlling leaf cell differentiation during drought stress in Brachypodium distachyon

An important challenge for today agriculture is to intensify worldwide cereal production in a sustainable manner in order to respond to the increasing food demand. Food production is limited mainly by biotic and abiotic stress and in particular by drought stress, the most common environmental factor affecting plant growth worldwide. For these reasons, the understanding of the complex molecular mechanisms involved in plant response during drought stresses is crucial for developing improved crop varieties better adapted to limiting environments. Brachypodium distachyon (Bd), a drought-tolerant wild grass, is an interesting model species to deeply study the molecular mechanisms involved in drought-stress response. With this aim, in this study a reproducible soil assay to subject Bd to drought stress was applied, which resulted in a drastically leaf size reduction. This effect was mainly caused by a reduction in cell expansion instead of a reduction of cell proliferation, underlining the insensitivity of the meristem to drought stress. Starting from this drastic phenotypic effect, the project, using Next Generation Sequencing (NGS) data provides a description of the molecular networks activated in response to drought, focusing on three different developmental zones (proliferation, expansion, and mature cells) of the third young developing Brachypodium leaf. More specifically, in order to investigate the mechanisms controlling leaf growth reduction during drought, the third emerging leaf was dissected in the three developmental zones and each zone was subjected to whole transcriptome analysis based on NGS. Eighteen libraries were sequenced, i.e. 3 cell types of leaf grown in control and drought condition, considering 3 biological replicates. Bioinformatics tools and statistical analyses were applied to NGS data, showing that distinct leaf cell zones respond differently to drought treatment. Moreover, the integration of mRNA-Seq data with small RNA-Seq data, previously produced by the lab, allowed to investigate the link between microRNAs and their putative target genes