Browsing by Subject "Resurrection plant"

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    A novel stress-inducible antioxidant enzyme identified from the resurrection plant Xerophyta viscosa Baker.
    (Springer, 2002) Mowla, Shaheen B; Thomson, Jennifer A; Farrant, Jill; Mundree, Sagadevan G
    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 °C), high light intensity (1,500 µmol photons m–2 s–1) and when treated with abscisic acid (100 µM 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.
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    Xylem hydraulic characteristics, water relations and wood anatomy of the resurrection plant Myrothamnus flabellifoliusWelw
    (Oxford University Press, 1998) Sherwin, Heather W; Pammenter, N W; February, E D; Vander Willigen, Clare; Farrant, Jill M
    Myrothamnus flabellifolius Welw. is a desiccation-tolerant (‘ resurrection’) plant with a woody stem. Xylem vessels are narrow (14 µm mean diameter) and perforation plates are reticulate. This leads to specific and leaf specific hydraulic conductivities that are amongst the lowest recorded for angiosperms (ks 0±87 kg m−" MPa−" s−"; kl 3±28¬10−& kg m−" MPa−" s−", stem diameter 3 mm). Hydraulic conductivities decrease with increasing pressure gradient. Transpiration rates in well watered plants were moderate to low, generating xylem water potentials of ®1 to ®2 MPa. Acoustic emissions indicated extensive cavitation events that were initiated at xylem water potentials of ®2 to ®3 MPa. The desiccation-tolerant nature of the tissue permits this species to survive this interruption of the water supply. On rewatering the roots pressures that were developed were low (2±4 kPa). However capillary forces were demonstrated to be adequate to account for the refilling of xylem vessels and re-establishment of hydraulic continuity even when water was under a tension of ®8 kPa. During dehydration and rehydration cycles stems showed considerable shrinking and swelling. Unusual knob-like structures of unknown chemical composition were observed on the outer surface of xylem vessels. These may be related to the ability of the stem to withstand the mechanical stresses associated with this shrinkage and swelling.