Multiomics analyses reveal the central role of the nucleolus and its machinery during heat stress acclimation in Pinus radiata.

Global warming is causing quick changes in mean annual temperature and more severe drought periods. These are major contributors of forest dieback, which is becoming more frequent and widespread. In this work we investigated how the transcriptome of Pinus radiata changed during initial heat stress response and acclimation. To this end, we generated a high-density dataset employing Illumina technology. This approach allowed us to reconstruct the needle transcriptome, defining 12164 and 13590 transcripts as down- and upregulated, respectively, during time course stress acclimation experiment. Additionally, the combination of transcriptome data with other available omics layers, allowed us to draw the complex interrelated processes involved in heat stress response from molecular to physiological level. Nucleolus and nucleoid activities seem to be a central core in acclimating process, producing specific RNA isoforms and other essential elements for anterograde-retrograde stress signaling as NAC proteins (Pra_vml_051671_1 and Pra_vml_055001_5) or Helicase RVB. These mechanisms are connected by elements already known in heat stress-response (redox, heat-shock proteins or ABA-related) and with others whose involvement is not so-well-defined as shikimate-related, brassinosteriods, or proline proteases together with their potential regulatory elements. This work provides a first deep overview about what molecular mechanisms underlying heat stress response and acclimation in Pinus radiata.