A
cDNA corresponding to 1-Cys
peroxiredoxin, an evolutionarily conserved
thiol-specific
antioxidant enzyme, was isolated from Xerophyta viscosa Baker, a resurrection plant indigenous to Southern Africa and belonging to the family Velloziaceae. The
cDNA, designated XvPer1, contains an open reading frame that encodes a
polypeptide of 219 residues with a predicted molecular weight of 24.2 kDa. The XvPer1
polypeptide shows significant sequence identity (approx. 70%) to other recently identified plant 1-Cys
peroxiredoxins and relatively high levels of sequence similarity (approx. 40%) to non-plant 1-Cys
peroxiredoxins. The XvPer1
cDNA contains a putative polyadenylation site. As for all 1-Cys
peroxiredoxins identified to date, the amino acid sequence proposed to constitute the active site of the
enzyme, PVCTTE, is highly conserved in XvPer1. It also contains a putative bipartite
nuclear localization signal. Southern blot analysis revealed that there is a single copy of XvPer1 in the X. viscosa genome. All angiosperm 1-Cys
peroxiredoxins described to date are seed-specific and absent in vegetative tissues even under stress conditions; therefore, XvPer1 is unique in that it is expressed in the vegetative tissues of X. viscosa. The XvPer1 transcript was absent in fully hydrated X. viscosa tissue but levels increased in tissues subjected to abiotic stresses such as
dehydration, heat (42 degrees C), high light intensity (1,500 micro mol photons m(-2) s(-1)) and when treated with
abscisic acid (100 micro M ABA) and
sodium chloride (100 mM NaCl). Western blot analyses correlated with the patterns of expression of XvPer1 transcripts under different stress conditions. Immunofluorescence analyses revealed that XvPer1 is localized in the nucleus of dehydrated X. viscosa leaf cells. These results suggest that XvPer1 is a stress-inducible gene, which may function to protect
nucleic acids within the nucleus against oxidative injury.