Browsing by Subject "resurrection plants"

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    Cell wall characteristics and structure of hydrated and dry leaves of the resurrection plant Craterostigma wilmsii, a microscopical study.
    (Elsevier, 1999) Vicré, M; Sherwin, H W; Driouich, A; Jaffer, M A; Farrant, J M
    The cell wall architecture of leaf tissues of the resurrection plant Craterostigma wilmsii at various stages of dehydration and rehydration was studied using electron microscopy and immunocytochemistry with antibodies to a hemicellulose (xyloglucan) and pectins. Upon dehydration, the cell walls were shown to fold extensively. It is thought that this folding may prevent excessive mechanical stress developing between the cell wall and the plasmalemma. Our immunocytochemical results show a significant increase in labelling of xyloglucan and unesterified pectins in the cell wall during drying, with levels declining again during rehydration. These components are known to play an important structural role within the cell wall, giving it more tensile strength. It is hypothesised that this increase in tensile strength allows the cell wall to contract and then fold as the plant dries and ultimately prevents the total inward collapse of the cell walls in dry tissue. The increased tensile strength may also be necessary to prevent the cell wall from unfolding and expanding too rapidly upon rehydration, thus allowing plasmalemma-cell wall connections to be reestablished.
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    Changes in leaf hexokinase activity and metabolite levels in response to drying in the desiccation?tolerant species Sporobolus stapfianus and Xerophyta viscosa.
    (Oxford University Press, 2001) Whittaker, Anne; Bochicchio, Adriana; Vazzana, Concetta; Lindsey, George; Farrant, Jill
    The phosphorylation of glucose and fructose is an important step in regulating the supply of hexose sugars for biosynthesis and metabolism. Changes in leaf hexokinase (EC 2.7.1.1) activity and in vivo metabolite levels were examined during drying in desiccation‐tolerant Sporobolus stapfianus and Xerophyta viscosa. Leaf hexokinase activity was significantly induced from 85% to 29% relative water content (RWC) in S. stapfianus and from 89% to 55% RWC in X. viscosa. The increase in hexokinase corresponded to the region of sucrose accumulation in both species, with the highest activity levels coinciding with region of net glucose and fructose removal. The decline of hexose sugars and accumulation of sucrose in both plant species was not associated with a decline in acid and neutral invertase. The increase in hexokinase activity may be important to ensure that the phosphorylation and incorporation of glucose and fructose into metabolism exceeded production from potential hydrolytic activity. Total cellular glucose‐6‐phosphate (Glc‐6‐P) and fructose‐6‐phosphate (Fru‐6‐P) levels were held constant throughout dehydration. In contrast to hexokinase, fructokinase activity was unchanged during dehydration. Hexokinase activity was not fully induced in leaves of S. stapfianus dried detached from the plant, suggesting that the increase in hexokinase may be associated with the acquisition of desiccation‐tolerance.
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    A proteomic investigation of the rhizomes of the resurrection fern Mohria caffrorum L. (Desv.) in response to desiccation
    (2015) Shoko, Ryman; Farrant, Jill M; Rafudeen, Mohamed S
    As there is limited information on the mechanisms of vegetative desiccation-tolerance in resurrection plant rhizomes, this work was undertaken to study the mechanisms of desiccation-tolerance in Mohria caffrorum rhizomes. Fronds of this plant have been previously characterized as being desiccation-tolerant in summer and desiccation-sensitive in winter. Since fern rhizomes are perennial organs, it was of interest to establish whether these organs are also perennially desiccation-tolerant and, whether or not the rhizomes regulate desiccation-tolerance in the fronds. Ultra-structural evidence using transmission electron microscopy and viability studies using electrolyte leakage analysis showed that the rhizomes were desiccation-tolerant throughout the seasons. Quantitative proteomics analysis using isobaric tags for relative and absolute quantification was employed to investigate molecular mechanisms of desiccation-tolerance in the rhizomes of this plant. Using a custom fern rhizome specific peptide sequence database, 236 proteins were identified. Of these, 16 proteins increased in abundance while 14 declined, in the summer collected rhizomes. On the other hand, 16 proteins increased in abundance and 20 declined in the winter form. Western blot analysis confirmed the expression trends of heat shock protein 70-2 and superoxide dismutase-[Cu-Zn], which were among the differentially expressed proteins. Bioinformatics analysis of the differentially expressed proteins was carried out using network enrichment tools, to identify key molecular processes and pathways involved in the rhizome response to desiccation stress. Results indicate that the rhizomes use different molecular mechanisms to achieve desiccation-tolerance in winter and summer. Potential cross-talks and cross-tolerances were identified in which mechanisms protecting the rhizomes against desiccation-tolerance appeared to also protect them against heat stress, and in winter an apparent cross-talk against desiccation and pathogen stresses was also identified. This study is the first report of evidence that M.caffrorum rhizomes are the 'master-regulator organs' responsible for regulating desiccation-tolerance in the fronds. This role was inferred from the rhizome's predicted up-/down-regulation of biological processes and pathways that relate to leaf senescence, shoot system morphogenesis and gametophyte development, among others.