Genomic Resources Development and Functional Characterization of Arundo Donax L. under Stress Conditions

Global warming is becoming a major threat for human and wildlife on Earth and scientists agree in considering anthropogenic greenhouse gasses emission as the main factor contributing to atmosphere and sea temperature increase. Arundo donax L. is the most promising species for second generation biofuel production in Mediterranean areas but up to now little was known about its genetics. In this study, we first explored the whole transcriptome of young shoot of Arundo donax under simulated drought stress through NGS technology. This allowed us to understand the general molecular mechanisms of early plant responses to osmotic stimulus. Through comparative analyses with major Poaceae species, we identified a set of 53 orthologs that can be considered as a core of evolutionary conserved genes important to mediate water stress responses in the family. Leveraging on the availability of this transcriptome, we developed a set of of reliable reference genes with high stability across different stress and/or tissues, to enable further functional studies in this species. We selected a candidate, named AdDWD1, that have the potential to play an important role in stress response by targeted protein degradation. Our results indicate that AdDWD1 is upregulated under osmotic and salt response in A. donax and its overexpression in Arabidopsis brought to a significant decrease in germination under salt and a growth retardation in ABA-containing media. Overexpression of AdDWD1 caused downregulation of DREB2A and SOS3, while it did not affect other stress-related genes, pinpointing a possible pathway-specific regulatory role of the gene. Taken together, these results suggest a strong relation of AdDWD1 with salt and osmotic stress response and an important role in the signalling pathway during early stress stages.