Project description:The periderm is basic for land plants due to its protective role during radial growth, which is achieved by the polymers deposited in the cell walls. Despite the research on the topic has unravelled the role of several enzymes and transcription factors, many questions remain open, especially those regarding cell development. Here we use the outer bark of cork oak (cork), holm oak (rhytidome), and their natural hybrids’ to further understand the mechanisms underlying periderm development. Cork is an outstanding model as it consists of a thick and very homogeneous periderm produced by a permanent mother-cell layer (phellogen). Conversely, holm oak contains a more heterogeneous bark including several thin periderms mixed with phloem, also known as a rhytidome. The inclusion of hybrid samples showing rhytidome-type and cork-type barks is valuable to approach cork development, allowing an accurate identification of candidate genes and processes. The present study underscores that biotic stress and cell death signalling are enhanced in rhytidome-type barks while lipid metabolism and cell cycle are enriched in cork-type barks. Based on the DEGs most expressed related to development, we highlight that cell division, cell expansion, and cell differentiation could account for the differences found between cork and rhytidome-type barks.
Project description:Cork quality is a technological trait of large interest for the Mediterranean cork industry. Our manuscript analyses the proteins and phenolics of cork producing cells in order to collect data about the molecular/biochemical pathways determining cork quality. To the best of our knowledge, this information is sparse in the research and technological community but it would be a valuable tool for breeding. We show that cells leading to the production stoppable (highly valued) and non-stoppable cork have contrasting profiles regarding soluble and cell-wall bound phenolics. The difference was also observed when considering the protein profiles but the discrimination between cork quality groups is not as remarkable as when considering phenolics. In any case, the mitochondrial metabolism points out for higher energy demand in non-stoppable cork producing cells.
Project description:Plants have developed specialized barriers to protect and isolate the inner tissues from the environment while maintaining homeostasis. Different barriers are present in various organs and at different growth stages. During secondary growth, the periderm acts as the protective tissue, covering roots, stems, and branches as they become thick. The periderm is a dynamic barrier comprising a stem cell niche known as the cork cambium, which bifacially divides to generate the phelloderm inward and the cork outward. Cork cells have a unique cell wall impregnated with suberin and lignin polymers, essential for the barrier function. Despite its importance, the differentiation process that forms new cork cells from the stem cell is largely unknown. In this work, we identify members of the MYB36-subclade transcription factors as key regulators of cork differentiation. On the one hand, this set of transcription factors promotes suberin deposition by inducing the expression of enzymes involved in all steps of suberin biosynthesis, including the recently discovered suberin-polymerizing enzymes GDS Lipases; on the other hand, it represses cork cambium proliferation. Furthermore, we demonstrated that suberin deposition in the cork is a robust process regulated by a complex network of transcription factors, including other MYB transcription factors that activate suberin deposition in the endodermis. However, only members of the MYB36 subclade can repress cell proliferation in different developmental contexts, highlighting general and specific functions for MYB transcription factors. These findings have broad applicability, as tissue-specific manipulation of MYB activity has the potential for improving traits of biotechnological interest, such as thicker periderms and more suberized cork layers, and for assessing how these traits affect plant performance in response to stresses.