Protection mechanisms in the resurrection plant Xerophyta viscosa (Baker): both sucrose and raffinose family oligosaccharides (RFOs) accumulate in leaves in response to water deficit

Abstract

Changes in water-soluble carbohydrates were examined in the leaves of the resurrection plant Xerophyta viscosa under conditions of water deficit. Sucrose and raffinose family oligosaccharides (RFOs), particularly raffinose, increased under these conditions, with the highest concentrations evident at 5% relative water content [RWC; 23.5 mg g(-1) dry weight (DW) and 17.7 mg g(-1) DW, respectively]. Importantly, these effects were reversible, with concentrations returning to levels comparable with that of the full turgor state 7 d after water deficit conditions were alleviated, providing evidence that both sucrose and RFOs may play a protective role in desiccated leaf tissue of X. viscosa. Further, because the sucrose-to-raffinose mass ratio of 1.3:1 observed in the dehydrated state was very low, compared with published data for other resurrection plants (always >5), it is suggested that, in X. viscosa leaves, RFOs serve the dual purpose of stress protection and carbon storage. XvGolS, a gene encoding a galactinol synthase enzyme responsible for the first catalytic step in RFO biosynthesis, was cloned and functionally expressed. In leaf tissue exposed to water deficit, XvGolS transcript levels were shown to increase at 19% RWC. GolS activity in planta could not be correlated with RFO accumulation, but a negative correlation was observed between RFO accumulation and myo-inositol depletion, during water deficit stress. This correlation was reversed after rehydration, suggesting that during water deficit myo-inositol is channelled into RFO synthesis, but during the rehydration process it is channelled to metabolic pathways related to the repair of desiccation-induced damage.

Heat Stress Related Physiological and Metabolic Traits in Peanut Seedlings

“…Among the sugar alcohols identified during this study, galactinol levels increased over 100 fold as a result of heat stress (Table 6). The osmoprotective and antioxidation roles of galactinol during abiotic stresses have been documented before (Nishizawa et al, 2008;Kaplan et al, 2004;Peters et al, 2007). In the present study, accumulation of galactinol in peanut plants is in agreement with this literature and highlights galactinol's role in heat stress tolerance of peanut seedlings (Kaplan et al, 2004).…”

The evolution of desiccation tolerance in angiosperm plants: a rare yet common phenomenon

“…Successful completion of the first phase allows the initiation of the second phase: (51-37% RWC, which is approaching the death point of desiccation-sensitive plants) a phase that proceeds in drying leaves independently of any connection with the plant. Protective sugars and LEA proteins accumulate rapidly, measures to prevent toxicity from oxidant free radicals and from ammonia are evident whilst nitrogenous compounds are remobilised ready to support recoverymetabolism in the event of subsequent leaf rehydration (Martinelli et al 2007;Oliver et al 2011a) -processes that are seen widely in resurrection species at these extreme water deficits (Illing et al 2005;Farrant 2007;Peters et al 2007).…”

Vacuolar Transport of Abscisic Acid Glucosyl Ester Is Mediated by ATP-Binding Cassette and Proton-Antiport Mechanisms in Arabidopsis

“…Fractions were collected every 3 min, concentrated to approximately 50 mL in a SpeedVac at 30°C, mixed with 3 mL of Ultima Gold scintillation cocktail (Perkin-Elmer), and measured by liquid scintillation counting. Additionally, 10 mL of the substrate mix was analyzed for the presence of [ 14 C]Glc by HPLC fractionation and subsequent liquid scintillation of 1-min fractions using the chromatographic system described by Peters et al (2007).…”