Transcriptomic profile and defense strategies in the red seaweed Laurencia dendroidea J. Agardh

Abstract

The red seaweed Laurencia dendroidea synthesizes diverse secondary metabolites that exhibit relevant ecological roles and biotechnological applications. Most of the studies regarding the genus Laurencia were dedicated to isolate and characterize these compounds although the molecular knowledge was still limited. This thesis describes the first transcriptomic profile of L. dendroidea and provides relevant information comprising the interactions between this seaweed and the associated microbiota in the molecular level. Using transcriptomic analysis, we verified the important contribution of L. dendroidea for the primary production of the holobiont and the role of Bacteria as consumers of organic matter and possibly as a nitrogen source. Despite the occurrence of a predominantly beneficial microbiome associated to L. dendroidea, some marine bacteria have the potential to cause diseases in seaweeds. In this context, the ability of seaweeds to defend against pathogens might have been evolutionarily selected. Here we describe the transcriptomic reprogramming of L. dendroidea in response to the potentially pathogenic bacteria Vibrio madracius. Some relevant metabolic processes over-represented in L. dendroidea in the presence of V. madracius were related to the production of reactive oxygen species, intracellular signaling, vesicle trafficking and energy conversion. Furthermore, most of the genes related to the biosynthesis of terpenes in L. dendroidea were described, which offers new possibilities for a heterologous biosynthesis of these compounds with biotechnological application. This thesis notably contributes to the current knowledge of the molecular mechanisms involved in the highly dynamic defense process in seaweeds. Keywords: holobiont, algae, bacteria, secondary metabolite, terpene, pathogen, defense, differential expression.