Abstract
Sugarcane (Saccharum spp. hybrids) is a potential lignocellulosic feedstock for biofuel production due to its exceptional biomass accumulation ability, high convertible carbohydrate content and a favorable energy input/output ratio. Genetic modification of biofuel traits to improve biomass conversion requires an understanding of the regulation of carbohydrate and lignin biosynthesis. RNA-Seq was used to investigate the transcripts differentially expressed between the immature and mature tissues of the sugarcane genotypes varying in fiber content. Most of the differentially expressed transcripts were found to be down-regulated during stem maturation, highlighting their roles in active secondary cell-wall development in the younger tissues of both high and low fiber genotypes. Several cellulose synthase genes (including CesA2, CesA4, CesA7 and COBRA-like protein), lignin biosynthesis-related genes (ρ-coumarate 3-hydroxylase, ferulate 5-hydroxylase, cinnamyl alcohol dehydrogenase and gentiobiase) and transcription regulators for the secondary cell-wall synthesis (including LIM, MYB, PLATZ, IAA24, C2H2 and C2C2 DOF zinc finger gene families) were exclusively differentially expressed between immature and mature tissues of high fiber genotypes. These findings reveal target genes for subsequent research on the regulation of cellulose and lignin metabolism.
Highlights
The use of biofuels to satisfy energy demand relies upon the development and efficient supply of suitable biomass as feedstock[1,2,3]
The genetic material chosen for the study included twenty sugarcane genotypes, categorized into two different groups of 10 high and 10 low fiber genotypes, which consisted of equal numbers of commercial genotypes and introgression lines derived from crosses between wild Saccharum spontaneum relatives and Erianthus species
The number of differentially expressed (DE) transcripts involved in cellulose synthase was identified for CesA2, CesA4; and 6 for CesA7. Taken this together with the results presented in the previous section, in terms on carbohydrate and sugar metabolism, this suggested that in the high fiber genotypes, the DE transcripts coding for CesA synthase (UDP-forming), COBRA-like proteins and endoglucanase 10 were down-regulated, whereas the transcripts coding for SPS (EC 2.4.1.14) and SuSy were down-regulated with fold change (FC) of 2.81 in the bottom internodes of high fiber
Summary
The use of biofuels to satisfy energy demand relies upon the development and efficient supply of suitable biomass as feedstock[1,2,3]. Knowledge of gene expression (hereafter used to mean expression of a transcript of the gene), regulation of polysaccharide and lignin metabolism in the developing sugarcane stems (especially of those contrasting genotypes for biomass traits) is limited with only a few genes identified through transcriptome profiling. In this present study, we used RNA-Seq analysis to compare the transcript profiles of the immature (forth internode from top) and mature (third internode from bottom) tissues of twenty sugarcane genotypes of high and low fiber, to highlight the gene expression differences between the tissue types from the two respective genotype groups. The current study focuses on differentially expressed (DE) genes/transcripts that are involved in cellulose and lignin biosynthesis, to identify potential genes/transcriptions factor for sugarcane biomass modification, thereby reducing the cost of pre-treatment for biofuel production
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