Abstract
BackgroundSugarcane is an emerging dual-purpose biofuel crop for energy and sugar production, owing to its rapid growth rate, high sucrose storage in the stems, and high lignocellulosic yield. It has the highest biomass production reaching 1.9 billion tonnes in 2014 worldwide.ResultsTo improve sugarcane biomass accumulation, we developed an interspecific cross between Saccharum officinarum ‘LA Purple’ and Saccharum robustum ‘MOL5829’. Selected F1 individuals were self-pollinated to generate a transgressive F2 population with a wide range of biomass yield. Leaf and stem internodes of fourteen high biomass and eight low biomass F2 extreme segregants were used for RNA-seq to decipher the molecular mechanism of rapid plant growth and dry weight accumulation. Gene Ontology terms involved in cell wall metabolism and carbohydrate catabolism were enriched among 3274 differentially expressed genes between high and low biomass groups. Up-regulation of cellulose metabolism, pectin degradation and lignin biosynthesis genes were observed in the high biomass group, in conjunction with higher transcript levels of callose metabolic genes and the cell wall loosening enzyme expansin. Furthermore, UDP-glucose biosynthesis and sucrose conversion genes were differentially expressed between the two groups. A positive correlation between stem glucose, but not sucrose, levels and dry weight was detected.ConclusionsWe thus postulated that the high biomass sugarcane plants rapidly convert sucrose to UDP-glucose, which is the building block of cell wall polymers and callose, in order to maintain the rapid plant growth. The gene interaction of cell wall metabolism, hexose allocation and cell division contributes to biomass yield.
Highlights
Sugarcane is an emerging dual-purpose biofuel crop for energy and sugar production, owing to its rapid growth rate, high sucrose storage in the stems, and high lignocellulosic yield
Expressed genes between high and low biomass sugarcane plants are enriched in cell wall metabolism To understand the molecular mechanism of fast-growing sugarcane with high dry weight accumulation, we developed an interspecific F2 population from the cross between Saccharum officinarum ‘LA Purple’ and Saccharum robustum ‘MOL5829’
Since a well-assembled Saccharum reference genome is not available, the RNAseq reads were aligned to the Sorghum bicolor annotated gene sequences; Gene Ontology (GO) and metabolic pathway analyses were based on sorghum gene models
Summary
Sugarcane is an emerging dual-purpose biofuel crop for energy and sugar production, owing to its rapid growth rate, high sucrose storage in the stems, and high lignocellulosic yield. It has the highest biomass production reaching 1.9 billion tonnes in 2014 worldwide. Cellulosic biofuel, which is bioenergy derived from the plant cell wall, is one of the main potential sources of renewable energy. Only 538 million liters were generated from cellulosic materials in 2015 (US EPA, 2015). By 2022, 61 billion liters of fuel for the US transportation industry should be generated from lignocellulosic feedstock [3]. A rapid improvement in biofuel crop breeding and facilities for energy extraction is necessary to meet the expected supply in 2022
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