Search Results (5)

While intensive aquaculture has developed rapidly, the consequent buildup of nitrogenous compounds, poses a critical threat to aquatic organisms. Microbial degradation offers an environmentally sustainable solution. We investigated the metabolic regulatory capacity of Priestia megaterium BZ-95 under four nitrogen regimes—ammonium (NH₄⁺-N), nitrite (NO₂⁻-N), nitrate (NO₃⁻-N), and a mixture of them (Mix)—using comparative transcriptomics. We revealed that BZ-95 in NH₄⁺-N activated a direct assimilation program prioritizing branched-chain amino acid biosynthesis. Conversely, under nitrate, BZ-95 enhanced membrane transport and 2-oxocarboxylic acid metabolism to facilitate the rapid incorporation of nitrate-derived ammonium into biomass. Nitrite stress triggered a coordinated response involving the assimilatory nir module (nirC-nirB-nirD) and enhanced energy metabolism to meet the heightened demand for reducing power during its rapid reduction. Under mixed nitrogen sources, BZ-95 established a highly synergistic carbon-nitrogen network, simultaneously processing multiple nitrogen inputs without a hierarchical preference, highlighting its remarkable metabolic plasticity. Intersection analysis defined a refined core of 692 nitrite-specific DEGs and revealed broad transcriptional activation under nitrite stress. Analysis of the NO₂⁻-specific core identified enhanced transmembrane transport capacity, coupled with auxiliary metabolic tuning, as central adaptive strategies for nitrite processing. Collectively, these findings provide crucial insights into the molecular basis of nitrogen coordination in P. megaterium BZ-95. Full article

Poor growth is often observed in artificial young forests due to insufficient inorganic nitrogen in karst soils. However, little is known about the assimilatory demand of the whole plant for nitrate and the partitioning of nitrate assimilation in roots and leaves in woody plants grown in karst habitats. In this study, Broussonetia papyrifera (L.) Vent (B. papyrifera) seedlings were grown under nearly hydroponic conditions. The isotope mass balance approach was employed to quantify the δ¹⁵N values of the N assimilates in plant organs and in whole plants for B. papyrifera seedlings grown at different nitrate concentrations. The δ¹⁵N values of the N assimilates in the whole B. papyrifera seedlings showed a rising trend with increasing nitrate concentration. Increasing the supply of nitrate decreased the leaf–root difference in the δ¹⁵N values of the N assimilates for B. papyrifera seedlings. Quantifying the δ¹⁵N values of N assimilates in the whole B. papyrifera seedlings grown under different nitrate concentrations contributes to estimating the assimilatory demand of the B. papyrifera seedlings for nitrate. The leaf–root difference in the δ¹⁵N values of the N assimilates can be used to estimate the partitioning of nitrate assimilation in the roots and leaves. Full article

The prospect of replacing traditional chemical fertilization with organic and microorganism-based fertilization meets the current demand for more sustainable cropping systems and healthy food. In this respect, research was carried out to evaluate the effects of the factorial combination between four basil cultivars (‘Aromat de Buzau’, ‘Macedon’, ‘Cuisoare’ and ‘Serafim’) and three types of fertilization, namely chemical fertilization (with a solid chemical fertilizer), organic fertilization (with chicken manure formulate) and microorganisms’ fertilization (with microorganisms formulate), on basil yield, biochemical and physiological parameters and essential oil composition. The results showed that the biometric parameters (plant height, number of stems and leaves and leaf area) were significantly influenced by the cultivar; ‘Macedon’ obtained the highest values of plant height (64.7 cm) and number of stems (20.33) and leaves (618.3) and ‘Serafim’ the largest leaf area (4901.7 cm² per plant), while the type of fertilization did not affect these parameters. Regarding the biomass, the influence of the cultivar was not significant on fresh biomass but was significant on dry biomass, with ‘Macedon’ showing the highest value (56.4 g·plant⁻¹ dry biomass). The mentioned parameters were significantly influenced by the type of fertilization, with the highest values recorded with chemical fertilization. Both the cultivar and the fertilization type significantly influenced the physiological parameters (the total content of assimilatory pigments and photosynthesis). Five phenolic compounds were quantified from leaf extracts by HPLC-MS (caffeic acid, hyperoside, isoquercitrin, rutin and quercitrin). Hyperoside was identified only in ‘Macedon’, while the rest of the compounds were found in all the cultivars and varied depending on the cultivar and fertilization type. Regarding the composition of the essential oil, variation was found depending on the cultivar and fertilization type. In ‘Aromat de Buzau’, the main compounds were methyl chavicol and β-linalool; in ‘Macedon’, geranial and neral; and in ‘Cuisoare’ and ‘Serafim’, β-linalool. Moreover, the PCA showed that the ‘Serafim’ cultivar has exclusive properties compared to the other cultivars. Our results highlight that identifying the most effective interaction between genotype and fertilization type allows to optimize yield and quality targets for sweet basil. Full article

In agricultural soils, nitrate (NO₃⁻) is the major nitrogen (N) nutrient for plants, but few studies have analyzed molecular and biochemical responses involved in its acquisition by grapevine roots. In viticulture, considering grafting, NO₃⁻ acquisition is strictly dependent on rootstock. To improve the knowledge about N nutrition in grapevine, this study analyzed biochemical and proteomic changes induced by, NO₃⁻ availability, in a hydroponic system, in the roots of M4, a recently selected grapevine rootstock. The evaluation of biochemical parameters, such as NO₃⁻, sugar and amino acid contents in roots, and the abundance of nitrate reductase, allowed us to define the time course of the metabolic adaptations to NO₃⁻ supply. On the basis of these results, the proteomic analysis was conducted by comparing the root profiles in N-starved plants and after 30 h of NO₃⁻ resupply. The analysis quantified 461 proteins, 26% of which differed in abundance between conditions. Overall, this approach highlighted, together with an increased N assimilatory metabolism, a concomitant rise in the oxidative pentose phosphate pathway and glycolysis, needed to fulfill the redox power and carbon skeleton demands, respectively. Moreover, a wide modulation of protein and amino acid metabolisms and changes of proteins involved in root development were observed. Finally, some results open new questions about the importance of redox-related post-translational modifications and of NO₃⁻ availability in modulating the dialog between root and rhizosphere. Full article

The response of plant N relations to the combination of elevated CO₂ (eCO₂) and warming are poorly understood. To study this, tomato (Solanum lycopersicum) plants were grown at 400 or 700 ppm CO₂ and 33/28 or 38/33 °C (day/night), and their soil was labeled with ¹⁵NO₃⁻ or ¹⁵NH₄⁺. Plant dry mass, root N-uptake rate, root-to-shoot net N translocation, whole-plant N assimilation, and root resource availability (%C, %N, total nonstructural carbohydrates) were measured. Relative to eCO₂ or warming alone, eCO₂ + warming decreased growth, NO₃⁻ and NH₄⁺-uptake rates, root-to-shoot net N translocation, and whole-plant N assimilation. Decreased N assimilation with eCO₂ + warming was driven mostly by inhibition of NO₃⁻ assimilation, and was not associated with root resource limitations or damage to N-assimilatory proteins. Previously, we showed in tomato that eCO₂ + warming decreases the concentration of N-uptake and -assimilatory proteins in roots, and dramatically increases leaf angle, which decreases whole-plant light capture and, hence, photosynthesis and growth. Thus, decreases in N uptake and assimilation with eCO₂ + warming in tomato are likely due to reduced plant N demand. Full article