Molecular and biochemical characterisation of a novel type II peroxiredoxin (XvPrx2) from the resurrection plant Xerophyta viscosa

Cloning, expression and enzymatic characteristics of a 2-Cys peroxiredoxin from Antarctic sea-ice bacterium Psychrobacter sp. ANT206

Peroxiredoxin (Prx, EC 1.11.1.15) is a family of the thiol-dependent antioxidant enzyme. In this study, a cold-adapted Prx gene from Antarctic psychrophilic bacterium Psychrobacter sp. ANT206 (PsPrx) consisted of an open reading frame (ORF) of 567 bp was cloned. Amino acid sequence analysis revealed that PsPrx contained one catalytic site (Thr45, Cys48 and Arg121) and could be categorized as a typical 2-Cys Prx. Compared with the mesophilic StPrx, PsPrx with a reduced amount of hydrogen bonds and salt bridges and other characteristics, may be responsible for its enzymatic stability and flexibility at low temperature. The recombinant PsPrx (rPsPrx) was purified to homogeneity by Ni-NTA and its enzymatic characterization was described. Interestingly, rPsPrx exhibited the maximum activity at 30 °C and remained 42.6% of its maximum activity at 0 °C. rPsPrx was a salt-tolerance enzyme that showed 42.2% of its maximum activity under 2.5 M NaCl. The kinetic parameters of different substrates revealed that it could efficiently catalyze the peroxides, especially H₂O₂ and t-BOOH (tert‑butyl hydroperoxide). Moreover, rPsPrx exhibited the ability to protect super-coiled DNA from oxidative damage. These results indicated that rPsPrx has special catalytic properties and may be a promising candidate for food and industrial applications.

Extremophyte adaptations to salt and water deficit stress

Plants that can survive and even thrive in extreme environments (extremophytes) are likely treasure boxes of plant adaptations to environmental stresses. These species represent excellent models for understanding mechanisms of stress tolerance that may not be present in stress-sensitive species, as well as for identifying genetic determinants to develop stress-tolerant crops. This special issue of Functional Plant Biology focuses on physiological and molecular processes that enable extremophytes to naturally survive high levels of salt or desiccation.