Desiccation of plants is often lethal but is tolerated by the majority of seeds and by vegetative tissues of only a small number of land plants. Desiccation tolerance is an ancient trait, lost from vegetative tissues following the appearance of tracheids but reappearing in several lineages when selection pressures favored its evolution. Cells of all desiccation-tolerant plants and seeds must possess a core set of mechanisms to protect them from desiccation- and rehydration-induced damage. This review explores how desiccation generates cell damage and how tolerant cells assuage the complex array of mechanical, structural, metabolic, and chemical stresses and survive.Likewise, the stress of rehydration requires appropriate mitigating cellular responses. We also explore what comparative genomics, both structural and responsive, have added to our understanding of cellular protection mechanisms induced by desiccation, and how vegetative desiccation tolerance circumvents destructive, stress-induced cell senescence.

Rice (Oryza sativa L.) is an important staple crop that feeds more than one half of the world’s population and is the model system for monocotyledonous plants. However, rice is very sensitive to salinity and is the most salt sensitive cereal crop with a threshold of 3 dSm⁻¹ for most cultivated varieties. Despite many attempts using different strategies to improve salinity tolerance in rice, the achievements so far are quite modest. This review aims to discuss challenges that hinder the improvement of salinity stress tolerance in rice as well as potential opportunities for enhancing salinity stress tolerance in this important crop.

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.

Global climate change, increasingly erratic weather and a burgeoning global population are significant threats to the sustainability of future crop production. There is an urgent need for the development of robust measures that enable crops to withstand the uncertainty of climate change whilst still producing maximum yields. Resurrection plants possess the unique ability to withstand desiccation for prolonged periods, can be restored upon watering and represent great potential for the development of stress tolerant crops. Here, we describe the remarkable stress characteristics of Tripogon loliiformis, an uncharacterised resurrection grass and close relative of the economically important cereals, rice, sorghum, and maize. We show that T. loliiformis survives extreme environmental stress by implementing autophagy to prevent Programmed Cell Death. Notably, we identified a novel role for trehalose in the regulation of autophagy in T.loliiformis. Transcriptome, Gas Chromatography Mass Spectrometry, immunoblotting and confocal microscopy analyses directly linked the accumulation of trehalose with the onset of autophagy in dehydrating and desiccated T. loliiformis shoots. These results were supported in vitro with the observation of autophagosomes in trehalose treated T. loliiformis leaves; autophagosomes were not detected in untreated samples. Presumably, once induced, autophagy promotes desiccation tolerance in T.loliiformis, by removal of cellular toxins to suppress programmed cell death and the recycling of nutrients to delay the onset of senescence. These findings illustrate how resurrection plants manipulate sugar metabolism to promote desiccation tolerance and may provide candidate genes that are potentially useful for the development of stress tolerant crops. Over coming decades, climate change models suggest that droughts and other unpredictable weather patterns will appear more frequently. It is imperative that we develop crops that can survive future climates but continue to yield. Numerous studies have shown that stress tolerance is genetically encoded. Naturally tolerant species therefore represent an ideal starting point for the search for stress tolerance. Resurrection plants belong to a small group of vascular plants that possess unique stress tolerance mechanisms to withstand extreme desiccation with the ability to recover fully upon the availability of water. Here we describe a unique regulatory role for trehalose in the activation of autophagy pathways in T.loliiformis. We show that T. loliiformis leaves are alive in desiccated plants and that pre-existing tissues resurrect upon the addition of water. By using a combination of transcriptomics, confocal microscopy and spectroscopy we show that autophagy is induced during dehydration. Notably, we establish that treatment of leaves with trehalose triggers autophagy in vitro and that trehalose accumulation in dehydrating leaves correlates with the presence of autophagosomes. We postulate that resurrection plants modulates trehalose metabolism to induce and maintain autophagy pathways that preventing senescence and programmed cell death.