No abstract

Urochloa (syn. Brachiaria spp.) is the most cultivated forage species in the tropics and is being introduced to agroecosystems as it can provide multiple services, such as nutrient cycling. In this regard, phosphorus (P) cycling has received particular attention for its little availability in soils and the fact that Urochloa has mechanisms to cope with its low availability. However, there are interspecific differences regarding adaptation to low fertility and P requirements among Urochloa species. This study aimed to evaluate the responses of three Urochloa species—Urochloa brizantha, Urochloa decumbens and Urochloa ruziziensis—to low P availability, as well as their mechanisms to grow on these conditions. We conducted a hydroponic experiment with three levels of P availability—10% (6.2 mg P dm−3), 25% (15.5 mg P dm−3) and 100% (62 mg P dm−3)—and evaluated plant biomass production, P tissue concentration, root acid phosphatase activity, root exudation and P transporter expression on roots. We identified several metabolites in root exudates including amino acids, non‐protein amino acids, polyamides, organic acids and phenolic acids. Although all metabolites were found in all the species, metabolite exudation varied among species and P level. Overall, U. brizantha and U. ruziziensis plants exudated more metabolites when growing under P limitation (10 and 25% P), which can be a response to low P availability and stress. We identified three P transporters in roots from the PHT1 family—UPHT1;1a, UPHT1;1b and UPHT1;1c. We did not find an explicit expression pattern for UPHT1;1a, but the expression of UPHT1;1b and UPHT1;1c increased at low P availability. U. ruziziensis accumulated more biomass than the other species at all levels of P availability, possibly because of the greater expression of these P transporters. Urochloa species differ regarding nutrient availability requirements, including P, which may explain the P transporters expression and metabolite exudation results. Thus, to cope with low P in the soil, the species developed different metabolic strategies to improve the uptake of this nutrient.

Plants often modify their metabolism in order to regain homeostasis and maintain survival in the face of stressful conditions. Here, two species of eucalyptus, E. globulus and E. grandis (adapted and non-adapted to low temperature, respectively), were exposed to either 10°C or 25°C over 24 h, and changes in gene expression and metabolite levels were analyzed. The aim of this experiment was to investigate the dynamic of short period changes in the energy metabolism of source (leaves) and sink (stem) tissues in these contrasting species regarding low temperature. We expected to observe a distinct pattern on carbon metabolism and source-to-sink relationship between both species which would be related to their different vegetative responses when facing low temperatures. In that way, E. globulus plants showed a differential expression in leaves and stems of SnRK1 genes system (responsible for energy availability control in plants), that was strongly associated to the changes in carbon metabolism and the main difference between the response when both species face cold. Taken together, the results suggest that low temperatures (10°C) are able to increase the sink strength of stem tissues and the carbon assimilation in leaves of E.

Cell suspension culture has been used as a model to study metabolic changes to several stresses. To have detailed information of nitrogen (N) limitation on sugarcane metabolism, a controlled study of the primary metabolites and representative compounds of secondary metabolism was developed using suspension cells growing under three different N regimes: normal condition (40 mmol•L -1 NO -3 ), slightly deficient (12 mmol•L -1 NO - 3) and completely deficient (0 mmol•L -1 NO -3 ). Sugarcane cells were harvested after 3 and 7 days of treatment. A range of changes in the levels of amino acids, organic acids, sugars and phenolic compounds were observed upon the growth conditions applied. Nitrogen limitation remarkably affected the amino acids and carbohydrates biosynthesis, which, associated with the changes observed on phenolic compounds contents, indicates the upregulation of carbon sink compensation mechanisms in these sugarcane cells exposed to N starvation. As expected, the results showed that N limitation might cause an extensive metabolic reprogramming of both carbon and N metabolism in sugarcane cells, and these changes are related to the intensity of the starvation. Nitrogen is essential for plant growth and development, and its limitation sharply reduces crop yield. Thus, these results open new perspectives for in planta studies concerning carbon and N metabolisms balance in this crop.

Aims Leifsonia xyli subsp. xyli (Lxx) is the most common sugarcane bacterial pathogen that affects plant development and primary metabolism. For example, cysteine and methionine are sulfur-containing essential amino acids used for bacterial growth and the title of Lxx in sugarcane plants might affect sulfur metabolism. The goal of this study were to evaluate how the increase in bacterial titers affects nutritional status and sulfur metabolism in sugarcane. Methods: The study was carried out with a susceptible sugarcane (Saccharum officinarum) genotype CB49260, with low and high Lxx titers, evaluating the mineral status and levels of primary metabolites. Results: Plants with high Lxx titers increased leaf sulfur content (S) compared to plants with low Lxx titers where plants with high Lxx titers displayed increased levels of sulfate, sucrose, maltose, raffinose, shikimic acid, malate, putrescine, glycerol, and, erythritol but decreased levels of methionine and glutathione in leaves. In the culm, plants with high Lxx titers displayed increased contents of maltose but decreased levels of threonine, ornithine, phenylalanine and myo-inositol when compared with plants with low Lxx titers. Conclusions: This study thus demonstrated that high bacterial titers increase sulfur demand in sugarcane. However, the increase in S content in the leaf did not result in higher sulfur assimilation, which was verified by increases sulfate level and decreases in methionine and glutathione levels. Therefore, our study showed that plant metabolism fails to meet the increased sulfur organic compound demand due to lower methionine and glutathione biosynthesis and methionine catabolism to putrescine biosynthesis in the leaves.

Aim: We previously published results of the BATTLE trial, showing that patients recently infected with SARS-CoV-2 can benefit from receiving Bacillus Calmette-Guérin (BCG) with minimal adverse effects. The study incorporated two strains of this vaccine. In this study, patient outcomes were compared based on the strain of BCG because different strains have been shown to have different immunogenicity. Methods: BATTLE was a double-blind controlled trial of COVID-19 convalescent patients; symptom progression, injection-site lesion characteristics and adverse effects were compared between recipients of placebo, Russian BCG strain or Brazilian BCG strains. Results: There was no statistically significant difference between the two BCG strains in terms of symptom progression, lesion-size or type. Conclusion: The two strains have similar clinical outcomes in COVID-19 convalescent patients.