Post-doctoral fellow, University of Cape Town
The ability of resurrection plants to withstand drought holds the key to make drought tolerant crops
Climate change is widely recognized as the major environmental problem the world is facing, with negative impacts on crop production and food security. The projections of increased global demand for crop calories and increased frequency and severity of drought episodes are expediting the development of crop varieties that can yield well under harsh environmental conditions. Developing countries are particularly at risk, as they struggle to maintain robust breeding capabilities and need support for the development of stress tolerant crops critical for food security. While efforts have been made to develop crops that better survive such conditions, few studies have improved the crop’s ability to tolerate drought. Such plants still die during extended droughts as they inevitably dehydrate below critical levels. It is thus imperative to rapidly find innovative solutions to minimise the potentially devastating impacts of drought. Research on plants that naturally tolerate both extreme water loss, such as resurrection plants, present a unique solution to this problem. The African resurrection plant Xerophyta viscosa is a close relative to cereal staple crops and thus can provide key information for the development of crop varieties better able to survive drought and produce a harvestable yield under drought. I study Xerophyta from a molecular and physiologic point of view to understand better the mechanisms it uses to tolerate extreme water loss. My goal is to identify which of these mechanisms can be used for plant breeders to create crop varieties able to tolerate drought without compromising yield. My team has already identified some of these mechanisms, such as the accumulation of protective molecules and powerful antioxidants. Our next step is to induce them in a crop and assess the efficacy in improving drought tolerance and the effects on yield under drought and optimal conditions.
Abstract: Water-deficit stress poses unique challenges to plant cells dependent on a hydrostatic skeleton and a polysaccharide-rich cell wall for growth and development. How the plant cell wall is adapted to loss of water is of interest in developing a general understanding of water stress tolerance in plants and of relevance in strategies related to crop improvement. Drought tolerance involves adaptations to growth under reduced water potential and the concomitant restructuring of the cell wall that allow growth processes to occur at lower water contents. Desiccation tolerance, by contrast, is the evolution of cell walls that are capable of losing the majority of cellular water without suffering permanent and irreversible damage to cell wall structure and polymer organization. This minireview highlights common features and differences between these two water-deficit responses observed in plants, emphasizing the role of the cell wall, while suggesting future research avenues that could benefit fundamental understanding in this area.
Pub.: 23 May '08, Pinned: 17 Aug '17
Abstract: Vegetative desiccation tolerance occurs in a unique group of species termed 'resurrection plants'. Here, we review the molecular genetic, physiological, biochemical, ultrastructural and biophysical studies that have been performed on a variety of resurrection plants to discover the mechanisms responsible for their tolerance. Desiccation tolerance in resurrection plants involves a combination of molecular genetic mechanisms, metabolic and antioxidant systems as well as macromolecular and structural stabilizing processes. We propose that a systems-biology approach coupled with multivariate data analysis is best suited to unraveling the mechanisms responsible for plant desiccation tolerance, as well as their integration with one another. This is of particular relevance to molecular biological engineering strategies for improving plant drought tolerance in important crop species, such as maize (Zea mays) and grapevine (Vitis vinifera).
Pub.: 31 Jan '09, Pinned: 17 Aug '17
Abstract: CRISPR/Cas enables precise improvement of commercially relevant crop species by transgenic and nontransgenic methodologies. We have used CRISPR/Cas with or without DNA repair template in both corn and soybean for a range of applications including enhancing drought tolerance, improving seed oil composition, and endowing herbicide tolerance. Importantly, by pairing CRISPR/Cas technology with recent advances in plant tissue culture, these changes can be introduced directly into commercially relevant genotypes. This powerful combination of technologies enables advanced breeding techniques for introducing natural genetic variations directly into product relevant lines with improved speed and quality compared with traditional breeding methods. Variation generated through such CRISPR/Cas enabled advanced breeding approaches can be indistinguishable from naturally occurring variation and therefore should be readily accessible for commercialization. The precision, reach, and flexibility afforded by CRISPR/Cas promise an important role for genome editing in future crop improvement efforts.
Pub.: 18 Jul '17, Pinned: 17 Aug '17
Abstract: In recent years, plant biotechnology has witnessed unprecedented technological change. Advances in high-throughput sequencing technologies have provided insight into the location and structure of functional elements within plant DNA. At the same time, improvements in genome engineering tools have enabled unprecedented control over genetic material. These technologies, combined with a growing understanding of plant systems biology, will irrevocably alter the way we create new crop varieties. As the first wave of genome-edited products emerge, we are just getting a glimpse of the immense opportunities the technology provides. We are also seeing its challenges and limitations. It is clear that genome editing will play an increased role in crop improvement and will help us to achieve food security in the coming decades; however, certain challenges and limitations must be overcome to realize the technology's full potential.
Pub.: 18 Jul '17, Pinned: 17 Aug '17
Abstract: Resurrection plants desiccate during periods of prolonged drought stress, then resume normal cellular metabolism upon water availability. Desiccation tolerance has multiple origins in flowering plants and it likely evolved through rewiring seed desiccation pathways. Oropetium thomaeum is an emerging model for extreme drought tolerance and its genome, which is the smallest among surveyed grasses, was recently sequenced. Combining RNA-seq, targeted metabolite analysis, and comparative genomics, we show evidence for co-option of seed specific pathways during vegetative desiccation. Desiccation related gene-coexpression clusters are enriched in functions related to seed development including several seed specific-transcription factors. Across the metabolic network, pathways involved in programed cell death inhibition, ABA signaling, and others are activated during dehydration. Oleosins and oil bodies that typically function in seed storage are highly abundant in desiccated leaves and may function for membrane stability and storage. Orthologs to seed-specific LEA proteins from rice and maize have neofunctionalized in Oropetium with high expression during desiccation. Accumulation of sucrose, raffinose, and stachyose in drying leaves mirrors sugar accumulation patterns in maturing seeds. Together, these results connect vegetative desiccation with existing seed desiccation and drought responsive pathways and provide some key candidate genes for engineering improved drought tolerance in crop plants.
Pub.: 22 Jul '17, Pinned: 17 Aug '17