The accumulation of trehalose (α-D-glucopyranosyl-[1,1]-α-D-glucopyranoside), a sugar with osmoprotectant properties, is very common in microorganisms, invertebrates and in resurrection plants. However, in the majority of higher plants, it is found in trace amounts. Trehalose is synthesized from the UDP-glucose and glucose-6-phosphate in a twostep process with two enzymes, trehalose-6-phosphate synthase or TPS (EC 2.4.1.15 and EC 2.4.1.36) and trehalose-6-phosphate phosphatase or TPP (EC 3.1.3.12). The trehalose-6-phosphate synthase and its product of the trehalose-6-phosphate (T6P) are probable signaling molecules in the carbohydrate metabolism, contributing to enhancing the plants tolerance to water stress. Water scarcity is one of the most important factors that influence productivity in sugarcane (Saccharum spp.) and it activates a cascade of metabolic events and necessary morphologic changes for the survival of the plant under stress. Here we show the in silico expression study of TPS in different libraries from the SUCEST project. Our results showed that the TPS genes are present in all tissues and that they are divided into two subfamilies (class I and II). It is shown that STPS1 belongs to the class I, therefore, it does not have an active phosphatase (TPP) domain, whereas, the STPS2 has an active TPP domain (class II) determined by the presence of phosphatase boxes. Expression analyses based on the semi-quantitative method of the reverse transcription polymerase chain reaction (RT-PCR) show that the STPS1 gene is up-regulated in the tolerant cultivar under stress and down-regulated in susceptible plants. The STPS2 gene does not show considerable variations in the expression levels under the same treatments. The discovery of active genes such as STPS1 and STPS2 in plants under water stress, contributes for the concerning about the cascade of responses in plants under water deficit and points out to target genes for plant breeding.

The potential of sugarcane as a food and bioenergy crop is currently driving the expansion of sugarcane production areas throughout the world. This crop may be constantly subjected to unusual environments such as acid soils with aluminum in toxic form (Al 3+), leading to problems in cultivation when the soil is not properly prepared. The aim of this research was to select most tolerant sugarcane genotypes to aluminum toxicity by determining root growth and proline content in the leaves. The experiment employed a factorial that was entirely randomized, with four sugarcane genotypes (CTC-2, CTC-14, RB855453, and RB966928) combined with aluminum concentrations (45, 88, 221, 444, 600, 897, 1000 µmol L-1), with three replications. Our results suggest that CTC-2 showed higher tolerance to aluminum, with more biomass accumulation in roots when compared to the other genotypes (descending order of tolerance: CTC-2 > CTC-14 > RB855453 > RB966928). Proline level was clearly different for tested genotypes. CTC-2 showed an increase of 58% in the proline level, while genotype RB855453 showed a 24% increase, but only when the aluminum concentration was 897µmolL-1 .

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