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Non-structural carbohydrate profiles and ratios between soluble sugars and starch serve as indicators of productivity for a bioenergy grass.

ABSTRACT: There is a pressing need to find a sustainable alternative to fossil fuels that will not compromise food security or require extensive use of agrochemicals. Miscanthus is a perennial energy grass predominantly used for combustion but with the current advancement of ligno-cellulosic fermentation technologies there is an interest in using Miscanthus for bioethanol production. Currently, the only commercially grown genotype of Miscanthus is M.× giganteus; a high yielding, interspecific hybrid of M. sacchariflorus and M. sinensis. As M.× giganteus is a sterile triploid, it cannot be used as a parent so Miscanthus breeding effort is focused on producing new interspecific varieties that out-perform M.× giganteus. The carbohydrate profiles of four genotypes of Miscanthus, including M. sacchariflorus (Sac-5), M.× giganteus (Gig-311), M. sinensis (Sin-11) and M. sinensis (Goliath), were characterized at replicated field sites in Aberystwyth, West Wales and Harpenden, south-east England. Our hypothesis was that a distinctive carbohydrate profile underlies enhanced biomass accumulation. Biomass accumulation is greatest when day-lengths and solar intensity are highest; so, observations were made in the middle of UK summer (July) for 2 years. Gig-311 had a greater abundance of fructose in its stems at both sites, and both Gig-311 and Sac-5 had low abundance of starch. At both sites, the highest yielding genotype was Gig-311 and Sac-5 was also high yielding at Harpenden, but performed comparatively poorly at Aberystwyth. At both sites Gig-311 had a distinctly high concentration of fructose, low starch and a high ratio of soluble sugars: starch, and at Harpenden, Sac-5 was similar. We conclude that the abundance of starch and fructose and a greater partitioning of soluble sugars, relative to starch, are candidate biomarkers of productivity in Miscanthus.

SUBMITTER: Purdy SJ

PROVIDER: S-EPMC5024741 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Non-structural carbohydrate profiles and ratios between soluble sugars and starch serve as indicators of productivity for a bioenergy grass.

Purdy Sarah Jane SJ Maddison Anne Louise AL Cunniff Jennifer J Donnison Iain I Clifton-Brown John J

AoB PLANTS 20150331

There is a pressing need to find a sustainable alternative to fossil fuels that will not compromise food security or require extensive use of agrochemicals. Miscanthus is a perennial energy grass predominantly used for combustion but with the current advancement of ligno-cellulosic fermentation technologies there is an interest in using Miscanthus for bioethanol production. Currently, the only commercially grown genotype of Miscanthus is M.× giganteus; a high yielding, interspecific hybrid of M. ...[more]

PMID: 25829378

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Project description:BackgroundMiscanthus, a C4 member of Poaceae, is a promising perennial crop for bioenergy, renewable bioproducts, and carbon sequestration. Species of interest include nothospecies M. x giganteus and its parental species M. sacchariflorus and M. sinensis. Use of biotechnology-based procedures to genetically improve Miscanthus, to date, have only included plant transformation procedures for introduction of exogenous genes into the host genome at random, non-targeted sites.ResultsWe developed gene editing procedures for Miscanthus using CRISPR/Cas9 that enabled the mutation of a specific (targeted) endogenous gene to knock out its function. Classified as paleo-allopolyploids (duplicated ancient Sorghum-like DNA plus chromosome fusion event), design of guide RNAs (gRNAs) for Miscanthus needed to target both homeologs and their alleles to account for functional redundancy. Prior research in Zea mays demonstrated that editing the lemon white1 (lw1) gene, involved in chlorophyll and carotenoid biosynthesis, via CRISPR/Cas9 yielded pale green/yellow, striped or white leaf phenotypes making lw1 a promising target for visual confirmation of editing in other species. Using sequence information from both Miscanthus and sorghum, orthologs of maize lw1 were identified; a multi-step screening approach was used to select three gRNAs that could target homeologs of lw1. Embryogenic calli of M. sacchariflorus, M. sinensis and M. x giganteus were transformed via particle bombardment (biolistics) or Agrobacterium tumefaciens introducing the Cas9 gene and three gRNAs to edit lw1. Leaves on edited Miscanthus plants displayed the same phenotypes noted in maize. Sanger sequencing confirmed editing; deletions in lw1 ranged from 1 to 26 bp in length, and one deletion (433 bp) encompassed two target sites. Confocal microscopy verified lack of autofluorescence (chlorophyll) in edited leaves/sectors.ConclusionsWe developed procedures for gene editing via CRISPR/Cas9 in Miscanthus and, to the best of our knowledge, are the first to do so. This included five genotypes representing three Miscanthus species. Designed gRNAs targeted all copies of lw1 (homeologous copies and their alleles); results also confirmed lw1 made a good editing target in species other than Z. mays. The ability to target specific loci to enable endogenous gene editing presents a new avenue for genetic improvement of this important biomass crop.

Project description:BackgroundMiscanthus is a commercial lignocellulosic biomass crop owing to its high biomass productivity, resilience and photosynthetic capacity at low temperature. These qualities make Miscanthus a particularly good candidate for temperate marginal land, where yields can be limited by insufficient or excessive water supply. Differences in response to water stress have been observed among Miscanthus species, which correlated to origin. In this study, we compared the physiological and molecular responses among Miscanthus species under excessive (flooded) and insufficient (drought) water supply in glasshouse conditions.ResultsA significant biomass loss was observed under drought conditions in all genotypes. M. x giganteus showed a lower reduction in biomass yield under drought conditions compared to the control than the other species. Under flooded conditions, biomass yield was as good as or better than control conditions in all species. 4389 of the 67,789 genes (6.4%) in the reference genome were differentially expressed during drought among four Miscanthus genotypes from different species. We observed the same biological processes were regulated across Miscanthus species during drought stress despite the DEGs being not similar. Upregulated differentially expressed genes were significantly involved in sucrose and starch metabolism, redox, and water and glycerol homeostasis and channel activity. Multiple copies of the starch metabolic enzymes BAM and waxy GBSS-I were strongly up-regulated in drought stress in all Miscanthus genotypes, and 12 aquaporins (PIP1, PIP2 and NIP2) were also up-regulated in drought stress across genotypes.ConclusionsDifferent phenotypic responses were observed during drought stress among Miscanthus genotypes from different species, supporting differences in genetic adaption. The low number of DEGs and higher biomass yield in flooded conditions supported Miscanthus use in flooded land. The molecular processes regulated during drought were shared among Miscanthus species and consistent with functional categories known to be critical during drought stress in model organisms. However, differences in the regulated genes, likely associated with ploidy and heterosis, highlighted the value of exploring its diversity for breeding.

Project description:Thellungiella halophila, a close relative of Arabidopsis, is a model halophyte used to study plant salt tolerance. The proteomic/physiological/transcriptomic analyses of Thellungiella plant leaves subjected to different salinity levels, reported herein, indicate an extraordinary ability of Thellungiella to adapt to large concentrations of exogenous saline by compartmentalizing Na(+) into cell vacuoles and accumulating proline and soluble sugars as organic osmolytes. Salinity stress stimulated the accumulation of starch in chloroplasts, which resulted in a greatly increased content of starch and total sugars in leaves. Comparative proteomics of Thellungiella leaves identified 209 salt-responsive proteins. Among these, the sequences of 108 proteins were strongly homologous to Arabidopsis protein sequences, and 30 had previously been identified as Thellungiella proteins. Functional classification of these proteins into 16 categories indicated that the majority are involved in carbohydrate metabolism, followed by those involved in energy production and conversion, and then those involved in the transport of inorganic ions. Pathway analysis revealed that most of the proteins are involved in starch and sucrose metabolism, carbon fixation, photosynthesis, and glycolysis. Of these processes, the most affected were starch and sucrose metabolism, which might be pivotal for salt tolerance. The gene expression patterns of the 209 salt-responsive proteins revealed through hierarchical clustering of microarray data and the expression patterns of 29 Thellungiella genes evaluated via quantitative RT-PCR were similar to those deduced via proteomic analysis, which underscored the possibility that starch and sucrose metabolism might play pivotal roles in determining the salt tolerance ability of Thellungiella. Our observations enabled us to propose a schematic representation of the systematic salt-tolerance phenotype in Thellungiella and suggested that the increased accumulation of starch, soluble sugars, and proline, as well as subcellular compartmentalization of sodium, might collectively denote important mechanisms for halophyte salt tolerance.

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Non-structural carbohydrate profiles and ratios between soluble sugars and starch serve as indicators of productivity for a bioenergy grass.

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Non-structural carbohydrate profiles and ratios between soluble sugars and starch serve as indicators of productivity for a bioenergy grass.

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