Drought stress is the major environmental stress that affects plant growth and productivity. It triggers a wide range of responses detectable at molecular, biochemical and physiological levels. At ...the molecular level the response to drought stress results in the differential expression of several metabolic pathways. For this reason, exploring the subtle differences in gene expression of drought sensitive and drought tolerant genotypes enables the identification of drought-related genes that could be used for selection of drought tolerance traits. Genome-wide RNA-Seq technology was used to compare the drought response of two sorghum genotypes characterized by contrasting water use efficiency.
The physiological measurements carried out confirmed the drought sensitivity of IS20351 and the drought tolerance of IS22330 genotypes, as previously studied. The expression of drought-related genes was more abundant in the drought sensitive genotype IS20351 compared to the tolerant genotype IS22330. Under drought stress Gene Ontology enrichment highlighted a massive increase in transcript abundance in the sensitive genotype IS20351 in "response to stress" and "abiotic stimulus", as well as for "oxidation-reduction reaction". "Antioxidant" and "secondary metabolism", "photosynthesis and carbon fixation process", "lipids" and "carbon metabolism" were the pathways most affected by drought in the sensitive genotype IS20351. In addition, genotype IS20351 showed a lower constitutive expression level of "secondary metabolic process" (GO:0019748) and "glutathione transferase activity" (GO:000004364) under well-watered conditions.
RNA-Seq analysis proved to be a very useful tool to explore differences between sensitive and tolerant sorghum genotypes. Transcriptomics analysis results supported all the physiological measurements and were essential to clarify the tolerance of the two genotypes studied. The connection between differential gene expression and physiological response to drought unequivocally revealed the drought tolerance of genotype IS22330 and the strategy adopted to cope with drought stress.
The biomass demand to fuel a growing global bio-based economy is expected to tremendously increase over the next decades, and projections indicate that dedicated biomass crops will satisfy a large ...portion of it. The establishment of dedicated biomass crops raises huge concerns, as they can subtract land that is required for food production, undermining food security. In this context, perennial biomass crops suitable for cultivation on marginal lands (MALs) raise attraction, as they could supply biomass without competing for land with food supply. While these crops withstand marginal conditions well, their biomass yield and quality do not ensure acceptable economic returns to farmers and cost-effective biomass conversion into bio-based products, claiming genetic improvement. However, this is constrained by the lack of genetic resources for most of these crops. Here we first review the advantages of cultivating novel perennial biomass crops on MALs, highlighting management practices to enhance the environmental and economic sustainability of these agro-systems. Subsequently, we discuss the preeminent breeding targets to improve the yield and quality of the biomass obtainable from these crops, as well as the stability of biomass production under MALs conditions. These targets include crop architecture and phenology, efficiency in the use of resources, lignocellulose composition in relation to bio-based applications, and tolerance to abiotic stresses. For each target trait, we outline optimal ideotypes, discuss the available breeding resources in the context of (orphan) biomass crops, and provide meaningful examples of genetic improvement. Finally, we discuss the available tools to breed novel perennial biomass crops. These comprise conventional breeding methods (recurrent selection and hybridization), molecular techniques to dissect the genetics of complex traits, speed up selection, and perform transgenic modification (genetic mapping, QTL and GWAS analysis, marker-assisted selection, genomic selection, transformation protocols), and novel high-throughput phenotyping platforms. Furthermore, novel tools to transfer genetic knowledge from model to orphan crops (i.e., universal markers) are also conceptualized, with the belief that their development will enhance the efficiency of plant breeding in orphan biomass crops, enabling a sustainable use of MALs for biomass provision.
•Truncation of RG-I galactan side-chains affected the hydration capacity.•In-vivo truncation of RG-I galactan side-chains reduced the hydration capacity.•In-vitro truncation of RG-I galactan ...side-chains increased the hydration capacity.
Potato cell walls (PCW) are a low value by-product from the potato starch industry. Valorisation of PCW is hindered by its high water-binding capacity (WBC). The composition of polysaccharides and interactions between these entities, play important roles in regulating the WBC in the cell wall matrix. Here, we show that in vivo exo-truncation of RG-I β-(1→4)-D-galactan side-chains decreased the WBC by 6–9%. In contrast, exo-truncation of these side-chains increased the WBC by 13% in vitro. We propose that degradation of RG-I galactan side-chains altered the WBC of PCW, due to cell wall remodelling and loosening that affected the porosity. Our findings reinforce the view that RG-I galactan side-chains play a role in modulating WBC, presumably by affecting polysaccharide architecture (spacing) and interactions in the matrix. Better understanding of structure-function relationships of pectin macromolecules is needed before cell wall by-products may be tailored to render added-value in food and biobased products.
The root bacterial microbiome is important for the general health of the plant. Additionally, it can enhance tolerance to abiotic stresses, exemplified by plant species found in extreme ecological ...niches like deserts. These complex microbe-plant interactions can be simplified by constructing synthetic bacterial communities or SynComs from the root microbiome. Furthermore, SynComs can be applied as biocontrol agents to protect crops against abiotic stresses such as high salinity. However, there is little knowledge on the design of a SynCom that offers a consistent protection against salt stress for plants growing in a natural and, therefore, non-sterile soil which is more realistic to an agricultural setting. Here we show that a SynCom of five bacterial strains, originating from the root of the desert plant Indigofera argentea, protected tomato plants growing in a non-sterile substrate against a high salt stress. This phenotype correlated with the differential expression of salt stress related genes and ion accumulation in tomato. Quantification of the SynCom strains indicated a low penetrance into the natural soil used as the non-sterile substrate. Our results demonstrate how a desert microbiome could be engineered into a simplified SynCom that protected tomato plants growing in a natural soil against an abiotic stress.
Chlorophyta, the group of green algae of which there are >6000 species, manifests a great diversity of intercellular and extracellular components. Building blocks in the cell walls of Chlorophyta are ...very distinct and they may contain various components. Here, we characterize the cell walls of Neochloris oleoabundans, a Chlorophyte microalga, both in terms of biochemical composition and morphology. N. oleoabundans cell walls are composed of about 24.3% carbohydrates, 31.5% proteins, 22.2% lipids and 7.8% inorganic material, which contrasts to the cell walls of (higher) terrestrial plants in which carbohydrates are by far the main component. We also observed that cell wall carbohydrates are mainly non-cellulosic polysaccharides, essentially composed of rhamnose, galactose, glucuronic acid and glucosamine, of which glucose is only a minor component. The lipids comprising the N. oleoabundans cell walls are generally wax/cutin-like. Electron microscopic studies revealed that N. oleabundans cell walls are approximately 200 nm thick and consist of two main layers: a thinner inner layer and a more electron-dense outer layer. On the outer layer are hair-like structures that are possibly rich in carbohydrates. These findings are an important contribution that enable us to understand the complexity of cell walls in green microalgae.
•Full biochemical composition and morphological structure of Neochloris oleoabundans cell wall were characterized.•Cell wall carbohydrates of N. oleoabundans are essentially composed of rhamnose, galactose, glucuronic acid and glucosamine.•Microscopy imaging shows that cell walls of N. oleoabundans are about 200 nm thick and consist of two main layers.•Wax/cutin-like lipids are potential targets for N. oleoabundans cell wall disruption during biorefining.
Protein crops have gained increasing interest in recent years, as a transition towards plant-protein based diets appears pivotal to ensure global food security and preserve the environment. The ...Andean species
Lupinus mutabilis
emerges as an ideal protein crop with great potential for Europe and other regions with temperate climates. This species is characterized by oil and protein content similar to soybean and is highly valued for its adaptability to colder climates and low input agriculture on marginal land. However, its introduction outside the Andes has yet to take off. To date,
L. mutabilis
remains an under-studied crop, lacking high yield, early maturity and a consistent breeding history. This review paper identifies
L. mutabilis
limitations and potential uses, and suggests the main breeding targets for further improvement of this crop. It also highlights the potential of new molecular tools and available germplasm resources that can now be used to establish
L. mutabilis
as a viable protein crop.
This study deals with approaches for a social-ecological friendly European bioeconomy based on biomass from industrial crops cultivated on marginal agricultural land. The selected crops to be ...investigated are: Biomass sorghum, camelina, cardoon, castor, crambe, Ethiopian mustard, giant reed, hemp, lupin, miscanthus, pennycress, poplar, reed canary grass, safflower, Siberian elm, switchgrass, tall wheatgrass, wild sugarcane, and willow. The research question focused on the overall crop growth suitability under low-input management. The study assessed: (i) How the growth suitability of industrial crops can be defined under the given natural constraints of European marginal agricultural lands; and (ii) which agricultural practices are required for marginal agricultural land low-input systems (MALLIS). For the growth-suitability analysis, available thresholds and growth requirements of the selected industrial crops were defined. The marginal agricultural land was categorized according to the agro-ecological zone (AEZ) concept in combination with the marginality constraints, so-called ‘marginal agro-ecological zones’ (M-AEZ). It was found that both large marginal agricultural areas and numerous agricultural practices are available for industrial crop cultivation on European marginal agricultural lands. These results help to further describe the suitability of industrial crops for the development of social-ecologically friendly MALLIS in Europe.
Lignocellulosic ethanol represents a renewable alternative to petrol. Miscanthus, a perennial plant that grows on marginal land, is characterized by efficient use of resources and is considered a ...promising source of lignocellulosic biomass. A life cycle assessment (LCA) was performed to determine the environmental impacts of ethanol production from miscanthus grown on marginal land in Great Britain (Aberystwyth) and an average‐yield site in Germany (Stuttgart; functional unit: 1 GJ). As the conversion process has substantial influence on the overall environmental performance, the comparison examined three pretreatment options for miscanthus. Overall, results indicate lower impacts for the production in Stuttgart in comparison with the corresponding pathways in Aberystwyth across the analysed categories. Disparities between the sites were mainly attributed to differences in biomass yield. When comparing the conversion options, liquid hot water treatment resulted in the lowest impacts, followed by dilute sulphuric acid. Dilute sodium hydroxide pretreatment represented the least favourable option. Site‐dependent variation in biomass composition and degradability did not have substantial influence on the environmental performance of the analysed pathways. Additionally, implications of replacing petrol with miscanthus ethanol were examined. Ethanol derived from miscanthus resulted in lower impacts with respect to greenhouse gas emissions, fossil resource depletion, natural land transformation and ozone depletion. However, for other categories, including toxicity, eutrophication and agricultural land occupation, net scores were substantially higher than for the fossil reference. Nevertheless, the results indicate that miscanthus ethanol produced via dilute acid and liquid hot water treatment at the site in Stuttgart has the potential to comply with the requirements of the European Renewable energy directive for greenhouse gas emission reduction. For ethanol production at the marginal site, carbon sequestration needs to be considered in order to meet the requirements for greenhouse gas mitigation.
Lignocellulosic ethanol represents a renewable alternative to petrol. Miscanthus, a perennial plant, is characterised by efficient resource use and is considered a promising source of lignocellulosic biomass. A LCA was performed to compare the environmental impacts of ethanol production from miscanthus grown on marginal land and an average‐yield site. In addition, three pretreatment options for miscanthus were compared. Results indicate lower impacts for the production at the average site, with the disparities mainly attributable to differences in biomass yield. Irrespective of the site, liquid hot water treatment has shown to be the pretreatment option with the lowest impacts overall.
Abstract
Plant cell walls of Poaceae and eudicots differ substantially, both in the content and composition of their components. However, the genomic and genetic basis underlying these differences is ...not fully resolved. In this research, we analyzed multiple genomic properties of 150 cell wall gene families across 169 angiosperm genomes. The properties analyzed include gene presence/absence, copy number, synteny, occurrence of tandem gene clusters, and phylogenetic gene diversity. Results revealed a profound genomic differentiation of cell wall genes between Poaceae and eudicots, often associated with the cell wall diversity between these plant groups. For example, overall patterns of gene copy number variation and synteny were clearly divergent between Poaceae and eudicot species. Moreover, differential Poaceae–eudicot copy number and genomic contexts were observed for all the genes within the BEL1-like HOMEODOMAIN 6 regulatory pathway, which respectively induces and represses secondary cell wall synthesis in Poaceae and eudicots. Similarly, divergent synteny, copy number, and phylogenetic gene diversification were observed for the major biosynthetic genes of xyloglucans, mannans, and xylans, potentially contributing to the differences in content and types of hemicellulosic polysaccharides differences in Poaceae and eudicot cell walls. Additionally, the Poaceae-specific tandem clusters and/or higher copy number of PHENYLALANINE AMMONIA-LYASE, CAFFEIC ACID O-METHYLTRANSFERASE, or PEROXIDASE genes may underly the higher content and larger variety of phenylpropanoid compounds observed in Poaceae cell walls. All these patterns are discussed in detail in this study, along with their evolutionary and biological relevance for cell wall (genomic) diversification between Poaceae and eudicots.
Genomic analyses on 150 cell wall gene families revealed highly divergent patterns between Poaceae and eudicots that are associated with the distinct cell wall properties of these two plant clades.
With the advent of biorefinery technologies enabling plant biomass to be processed into biofuel, many researchers set out to study and improve candidate biomass crops. Many of these candidates are C4 ...grasses, characterized by a high productivity and resource use efficiency. In this review the potential of five C4 grasses as lignocellulosic feedstock for biofuel production is discussed. These include three important field crops-maize, sugarcane and sorghum-and two undomesticated perennial energy grasses-miscanthus and switchgrass. Although all these grasses are high yielding, they produce different products. While miscanthus and switchgrass are exploited exclusively for lignocellulosic biomass, maize, sorghum, and sugarcane are dual-purpose crops. It is unlikely that all the prerequisites for the sustainable and economic production of biomass for a global cellulosic biofuel industry will be fulfilled by a single crop. High and stable yields of lignocellulose are required in diverse environments worldwide, to sustain a year-round production of biofuel. A high resource use efficiency is indispensable to allow cultivation with minimal inputs of nutrients and water and the exploitation of marginal soils for biomass production. Finally, the lignocellulose composition of the feedstock should be optimized to allow its efficient conversion into biofuel and other by-products. Breeding for these objectives should encompass diverse crops, to meet the demands of local biorefineries and provide adaptability to different environments. Collectively, these C4 grasses are likely to play a central role in the supply of lignocellulose for the cellulosic ethanol industry. Moreover, as these species are evolutionary closely related, advances in each of these crops will expedite improvements in the other crops. This review aims to provide an overview of their potential, prospects and research needs as lignocellulose feedstocks for the commercial production of biofuel.
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