Wide distribution of D-xylose dehydrogenase in yeasts reveals a new element in the D-xylose metabolism for bioethanol production.

D-xylose utilization by yeasts is an essential feature for improving second-generation ethanol production. However, industrial yeast strains are incapable of consuming D-xylose. Previous analyzes of D-xylose-consuming or fermenting yeast species reveal that the genomic features associated with this phenotype are complex and still not fully understood. Here we present a previously neglected yeast enzyme related to D-xylose metabolism, D-xylose dehydrogenase (XylDH), which is found in at least 105 yeast genomes. By analyzing the XylDH gene family, we brought evidence of gene evolution marked by purifying selection on codons and positive selection evidence in D-xylose-consuming and fermenting species, suggesting the importance of XylDH for D-xylose-related phenotypes in yeasts. Furthermore, although we found no putative metabolic pathway for XylDH in yeast genomes, namely the absence of three bacterial known pathways for this enzyme, we also provide its expression profile on D-xylose media following D-xylose reductase for two yeasts with publicly available transcriptomes. Based on these results, we suggest that XylDH plays an important role in D-xylose usage by yeasts, likely being involved in a cofactor regeneration system by reducing cofactor imbalance in the D-xylose reductase pathway.

Internode elongation in energy cane shows remarkable clues on lignocellulosic biomass biosynthesis in Saccharum hybrids.

Energy cane is a dedicated crop to high biomass production and selected during Saccharum breeding programs to fit specific industrial needs for 2G bioethanol production. Internode elongation is one of the most important characteristics in Saccharum hybrids due to its relationship with crop yield. In this study, we selected the third internode elongation of the energy cane. To characterize this process, we divided the internode into five sections and performed a detailed transcriptome analysis (RNA-Seq) and cell wall characterization. The histological analyses revealed a remarkable gradient that spans from cell division and protoxylem lignification to the internode maturation and complete vascular bundle lignification. RNA-Seq analysis revealed more than 11,000 differentially expressed genes between the sections internal. Gene ontology analyzes showed enriched categories in each section, as well as the most expressed genes in each section, presented different biological processes. We found that the internode elongation and division zones have a large number of unique genes. Evaluated the specific profile of genes related to primary and secondary cell wall formation, cellulose synthesis, hemicellulose, lignin, and growth-related genes. For each section these genes presented different profiles along the internode in elongation in energy cane. The results of this study provide an overview of the regulation of gene expression of an internode elongation in energy cane. Gene expression analysis revealed promising candidates for transcriptional regulation of energy cane lignification and evidence key genes for the regulation of internode development, which can serve as a basis for understanding the molecular regulatory mechanisms that support the growth and development of plants in the Saccahrum complex.

Metabolite profiles of energy cane and sugarcane reveal different strategies during the axillary bud outgrowth.

Commercial cultivation of sugarcane is usually carried out by planting culm segments (sett) carrying buds in their internodes. However, this is an inefficient practice due to high sprouting irregularity. In this work, we inspect the first stages of the physiological preparation of the culm for sprouting, trying to identify compounds that actively participate in this process. We compared, during the first 48 h, the metabolic profile of sugarcane against energy cane, a cultivar known to have higher sprouting speed and consistency. In fact, during this short period it was possible to observe that energy cane already had a higher physiological activity than sugarcane, with significant changes in the catabolism of amino acids, increased levels of reducing sugars, lipids and metabolic activity in the phenylpropanoid pathway. On the other hand, sugarcane samples had just begun their activity during this same period, with an increase in the level of glutamate as the most significant change, which may be linked to the strategy of these cultivars to develop their roots before leaves, opposite of what is seen for energy cane. These results contribute to the development of strategies for increasing the efficiency of sprouting in sugarcane.