Characterization of the Cork Formation and Production Transcriptome in × Hybrids

Cork oak is the main cork-producing species worldwide, and plays a significant economic, ecological and social role in the Mediterranean countries, in particular in Portugal and Spain. The ability to produce cork is limited to a few species, hence it must involve specific regulation mechanisms that are unique to these species. However, to date, these mechanisms remain largely understudied, especially with approaches involving the use of high-throughput sequencing technology. In this study, the transcriptome of cork-producing and non-cork-producing  ×  hybrids was analyzed in order to elucidate the differences between the two groups of trees displaying contrasting phenotypes for cork production. The results revealed the presence of a significant number of genes exclusively associated with cork production, in the trees that developed cork. Moreover, several gene ontology subcategories, such as cell wall biogenesis, lipid metabolic processes, metal ion binding and apoplast/cell wall, were only detected in the trees with cork production. These results indicate the existence, at the transcriptome level, of mechanisms that seem to be unique and necessary for cork production, which is an advancement in our knowledge regarding the genetic regulation behind cork formation and production.