Dynamics of the Spanish fir transcriptome in nature: Metabolic pathways and gene networks involved in the response to climate stress

Mediterranean forests such as those integrated by Spanish firs in southern Spain are extremely sensitive to the effects of climate climate-driven stresses. Recurrent periods of drought and prolonged warming in the last few years are major factors involves in the current vulnerability of local populations. In this work, physiological and transcriptional analyses were combined to assess the response of trees growing in the forest under natural conditions. The results show a modulation of the transcriptome in response to climatic stress with substantial changes in the expression of genes involved in water stress, aromatic amino acid metabolism, and transcription factors associated with the transcriptional regulation of the observed patterns of gene expression. Roots were determined to be the primary organs involved in the transcriptional response to stress which may be mediated by a gene-network including interactions among structural and regulatory genes. Interactive elements comprise genes encoding stress-related proteins of the ApLEA family, ApADH, the first committed enzyme in tyrosine biosynthesis, and root-specific transcription factors implicated in stress regulation belonging to the ApERF, ApYABBY and ApNAC superfamilies. Data provide new insights to understand the response of Spanish firs to current climatic disturbances by the identification of individual genes and gene-networks potentially involved in local adaptation. This new knowledge will facilitate comparative studies of gene variation in the Spanish fir populations using the identified genes as molecular markers for selection of the best adapted genotypes in the response of climate stress. Overall design: In this study, needles and roots from adult Abies pinsapo trees (30–50 years old) were analyzed. To examine the effect of climatic variations on the tree transcriptome dynamics, tissue samples were collected from two different organs (needles and roots) at both sites (YUN and RON) and during both seasons, spring (SPR) and autumn (AUT). On each occasion, needles and roots were harvested at midday from ten randomly selected adult individuals (30-50 yr-old trees) of A. pinsapo.