Exploring the mechanisms underlying recovery from freeze-thaw injury in Colobanthus quitensis: mechanistic insights via transcriptome profiling.

Antarctic plants face significant challenges due to exposure to freeze-thaw stress throughout their life cycle. The ability to recover from freeze-thaw injuries during post-thaw recovery (PTR) periods is a crucial skill for their survival and growth. However, no research, to the best our knowledge, has explored their recovery mechanisms at the cellular and molecular levels. To investigate the potential cellular mechanism during PTR periods, we focused on Colobanthus quitensis, one of solely two vascular plant species in the Antarctic Peninsula. Having determined the lethal temperature causing 50% cellular injury (LT) under freezing to be -8.0°C, we subjected plants to sub-injurious (-7.0°C) and injurious (-9.0°C) freezing treatments. We then compared recovery abilities at these stress levels using physiological indicators such as ion-leakage, PSII quantum efficiency (Fv/Fm), and antioxidant enzyme activities. Comparative analysis indicated that plants exposed to -7.0°C progressively recovered during PTR periods, showing reduced ion-leakage and increased Fv/Fm, while those stressed at -9.0°C exhibited irrecoverable damage with lower antioxidant enzymes activities. To investigate the molecular basis of recovery, we examined transcriptome changes in tissues exposed to -7.0°C during PTR periods through GO and KEGG pathway enrichment analyses. These analyses identified six potential cellular events involved in the recovery process, including ionic & pH homeostasis, cell wall remodeling, protein repair, defense against potential microbial attacks, free radical scavenging, and DNA repair. Understanding the cellular and molecular mechanisms of recovery from freeze-thaw injuries enhances our knowledge on how Antarctic plants adapt to extreme environments, offering valuable insights into their survival strategies.