Bioinformatic analyses to uncover genes involved in trehalose metabolism in the polyploid sugarcane.

Trehalose-6-phosphate (T6P) is an intermediate of trehalose biosynthesis that plays an essential role in plant metabolism and development. Here, we comprehensively analyzed sequences from enzymes of trehalose metabolism in sugarcane, one of the main crops used for bioenergy production. We identified protein domains, phylogeny, and in silico expression levels for all classes of enzymes. However, post-translational modifications and residues involved in catalysis and substrate binding were analyzed only in trehalose-6-phosphate synthase (TPS) sequences. We retrieved 71 putative full-length TPS, 93 trehalose-6-phosphate phosphatase (TPP), and 3 trehalase (TRE) of sugarcane, showing all their conserved domains, respectively. Putative TPS (Classes I and II) and TPP sugarcane sequences were categorized into well-known groups reported in the literature. We measured the expression levels of the sequences from one sugarcane leaf transcriptomic dataset. Furthermore, TPS Class I has specific N-glycosylation sites inserted in conserved motifs and carries catalytic and binding residues in its TPS domain. Some of these residues are mutated in TPS Class II members, which implies loss of enzyme activity. Our approach retrieved many homo(eo)logous sequences for genes involved in trehalose metabolism, paving the way to discover the role of T6P signaling in sugarcane.

Polyamine- and Amino Acid-Related Metabolism: The Roles of Arginine and Ornithine are Associated with the Embryogenic Potential.

The mechanisms that control polyamine (PA) metabolism in plant cell lines with different embryogenic potential are not well understood. This study involved the use of two Araucaria angustifolia cell lines, one of which was defined as being blocked, in that the cells were incapable of developing somatic embryos, and the other as being responsive, as the cells could generate somatic embryos. Cellular PA metabolism was modulated by using 5 mM arginine (Arg) or ornithine (Orn) at two time points during cell growth. Two days after subculturing with Arg, an increase in citrulline (Cit) content was observed, followed by a higher expression of genes related to PA catabolism in the responsive cell line; whereas, in the blocked cell line, we only observed an accumulation of PAs. After 14 d, metabolism was directed towards putrescine accumulation in both cell lines. Exogenous Arg and Orn not only caused a change in cellular contents of PAs, but also altered the abundance of a broader spectrum of amino acids. Specifically, Cit was the predominant amino acid. We also noted changes in the expression of genes related to PA biosynthesis and catabolism. These results indicate that Arg and Orn act as regulators of both biosynthetic and catabolic PA metabolites; however, we suggest that they have distinct roles associated with embryogenic potential of the cells.

Quantitative proteomic analysis of Araucaria angustifolia (Bertol.) Kuntze cell lines with contrasting embryogenic potential.

GeLC­MS/MS based label free proteomic profiling was used in the large scale identification and quantification of proteins from Brazilian pine (Araucaria angustifolia) embryogenic cell (EC) lines that showed different propensities to form somatic embryos. Using a predicted protein sequence database that was derived from A. angustifolia RNA-Seq data, 2398 non-redundant proteins were identified. The log2 of the spectral count values of 858 proteins of these proteins showed a normal distribution, and were used for statistical analysis. Statistical tests indicated that 106 proteins were significantly differentially abundant between the two EC lines, and that 35 were more abundant in the responsive genotype (EC line SE1) and 71 were more abundant in the blocked genotype (EC line SE6). An increase in the abundance of proteins related to cell defense, anti-oxidative stress responses, and storage reserve deposition was observed in SE1. Moreover, in SE6 we observed an increased abundance of two proteins associated with seed development during the embryogenic cell proliferation stage, which we suggest is associated with genotypes showing a low responsiveness to embryo formation. Differences in protein abundance between the EC lines are discussed in terms of carbohydrate metabolism, cell division, defense response, gene expression, and response to reactive oxygen species.