Glutamate dehydrogenase mediated amino acid metabolism after ammonium uptake enhances rice growth under aeration condition.

KEY MESSAGE: Aeration stimulates the rice growth and nitrogen (N) metabolism; in which, the glutamate accumulation limited by the glutamate dehydrogenase pathway after ammonia uptake may control root N metabolism during aeration. Increasing rhizosphere oxygen content greatly improves rice growth and biomass. To study the intrinsic mechanism involved in nitrogen (N) metabolism, a hydroponic experiment was conducted by supplying two different oxygen levels to two different rice genotypes. Compared to the hypoxia-resistant cultivar (Nip; japonica rice 'Nipponbare'), the hypoxia-sensitive cultivar (U502; upland rice 'Upland 502') presented with severe oxidative damage under the lack of aeration. However, aeration significantly reduced root oxidative damage by enhancing root antioxidant capacity and leaf photosynthesis especially in U502, and significantly increased nitrate (NO3-) and ammonia (NH4+) uptake and upregulated the expression of the genes controlling these processes. Additional NO3- was mainly incorporated into amino acids in the leaves whereas NH4+ assimilation occurred mostly in the roots. The 15N gas chromatography-mass spectrometry analysis demonstrated that aeration had no influence on the compositions of the individual amino acids derived from 15NO3- in the roots, but increased labeled glutamic acid (Glu), asparagine, γ-aminobutyric acid, and alanine in 15NH4+-treated roots. Aeration inhibited root glutamate synthetase activity but this did not inhibit 15N-Glu production from 15NH4+. In contrast, aeration upregulated isocitrate dehydrogenase and glutamate dehydrogenase. These mechanisms and soluble carbohydrates may constitute an alternative pathway for Glu production in which amino acid metabolism is enhanced after NH4+ uptake during aeration. Therefore, the rice growth-enhancing effect of aeration is closely correlated with root redox equilibrium, N uptake, and amino acid metabolism. Glutamic acid accumulation is limited by the glutamate dehydrogenase pathway after NH4+ uptake and may control root N metabolism during aeration.

Variability of leaf photosynthetic characteristics in rice and its relationship with resistance to water stress under different nitrogen nutrition regimes.

The negative effects of water stress on rice can be alleviated by NH4 + nutrition. However, the effects of mixed nitrogen (N) nutrition (NO3 - + NH4 + ) on resistance to water stress are still not well known. To investigate the response of rice growth to water stress and its relationship with photosynthetic characteristics, a hydroponic experiment supplying different N forms was conducted. Compared with NO3 - nutrition, mixed-N and NH4 + nutrition greatly alleviated the reduction of leaf area, chlorophyll content, and photosynthesis under water stress, whilst subsequently maintaining higher biomass. In contrast, water stress inhibited the root-shoot ratios in NH4 + - and mixed-N-supplied plants, indicating reduced root growth and higher photosynthate availability to shoots. The following key observations were made: (1) a similar stomatal limitation and low proportion of activated Rubisco were observed among the three different N nutrition regimes; (2) increased mesophyll conductance in NH4 + - and mixed-N-supplied plants simultaneously stimulated leaf photosynthesis and improved the water use efficiency and (3), the maximum carboxylation rate and actual photochemical efficiency of photosystem II in NH4 + - and mixed-N-supplied plants were significantly higher than that in NO3 - -supplied plants, thus resulting in higher photochemical efficiency under water stress. In conclusion, mixed-N and NH4 + nutrition may be used to develop strategies for improved water stress resistance and stimulated biomass production under conditions of osmotic stress and possibly drought.

Habitat evaluation of wild Amur tiger (Panthera tigris altaica) and conservation priority setting in north-eastern China.

The Amur Tiger (Panthera tigris altaica) is one of the world's most endangered species. Recently, habitat fragmentation, food scarcity and human hunting have drastically reduced the population size and distribution areas of Amur tigers in the wild, leaving them on the verge of extinction. Presently, they are only found in the north-eastern part of China. In this study, we developed a reference framework using methods and technologies of analytic hierarchy process (AHP), remote sensing (RS), geographic information system (GIS), GAP analysis and Natural Break (Jenks) classification to evaluate the habitat and to set the conservation priorities for Amur tigers in eastern areas of Heilongjiang and Jilin Provinces of northeast China. We proposed a Habitat Suitability Index (HSI) incorporating 7 factors covering natural conditions and human disturbance. Based on the HSI values, the suitability was classified into five levels from the most to not suitable. Finally, according to results of GAP analysis, we identified six conservation priorities and designed a conservation landscape incorporating four new nature reserves, enlarging two existing ones, and creating four linkages for Amur tigers in northeast China. The case study showed that the core habitats (the most suitable and highly suitable habitats) identified for Amur tigers covered 35,547 km(2), accounting for approximately 26.71% of the total study area (1,33,093 km(2)). However, existing nature reserves protected only (7124 km(2) or) 20.04% of the identified core habitats. Thus, enlargement of current reserves is necessary and urgent for the tiger's conservation and restoration. Moreover, the establishment of wildlife corridors linking core habitats will provide an efficient reserve network for tiger conservation to maintain the evolutionary potential of Amur tigers facing environmental changes.

Clinical research of ankle fusion with vascularised semi-split fibular flap via lateral approach / 中华显微外科杂志

Objective:To investigate the clinical efficacy of the vascularised semi-split fibular flap with lateral approach in ankle fusion.Methods:A total of 54 patients who underwent ankle fusion through the lateral menstrual approach by the Department of Trauma and Micro Orthopaedics, Zhongnan Hospital of Wuhan University from June 2015 to December 2020 was retrospectively analysed. Of the 54 patients, 27 patients who underwent ankle fusion with a semi-split fibular flap carrying blood supply were assigned to the fibular flap group, while other 27 patients who had ankle fusion with lateral plate were assigned to the plate group. The ankle fusions for both groups were performed by the same surgical team. The clinical efficacy of the 2 groups was evaluated by the success rate of bone fusion, the American Orthopedic Foot and Ankle Surgery(AOFAS) Ankle-Hindfoot Score System, and the Visual analog score(VAS). All the patients entered the postoperative follow-up at outpatient clinic.Results:The follow-up lasted for 12-24 months, with an average of 15 months. At 6 months after surgery, 24 patients in the fibular flap group achieved osseous union with 88.9% in the success rate of bone fusion. While 17 patients in the plate group achieved osseous union, with the success rate of bone fusion at 63.0%. There was a statistically significant difference between the groups( P<0.05). At 1 year after surgery, all 27 patients in the fibular flap group achieved bony union, with a 100% of the success rate of bone fusion, while 23 patients in the plate group achieved bony union at a 85.2% success rate of bone fusion, with 4 patients failed to heal. The difference was statistically significant( P<0.05). The AOFAS scores of the fibular flap group were 41.3±12.0, 65.6±5.6, and 79.1±7.0 before operation, at 6 months after operation and 1 year after operation, respectively, while the scores for the plate group at the same time were 40.8±11.3, 64.5±4.1 and 69.3±7.2. There was no significant difference in the scores between the groups before surgery and at 6 months after the operation ( P>0.05). The scores at 1 year after surgery in the fibular flap group was significantly higher than the plate group, and there was a statistically significant difference( P<0.05). The preoperative VAS score in the fibular flap group was 7.6±1.3, while it was 7.5±1.1 in the plate group. There was no significant difference between the groups in VAS score( P>0.05). However, the VAS score at 1 year after surgery was found at 1.8±0.9 in the plate group, and 1.9±0.8 in the fibular flap group and the difference between groups was statistically significant( P<0.05). Conclusion:The surgical procedure of semi-split fibular flap through the lateral approach has lower complications and higher success rate in ankle fusion in comparison with those of the fusion with lateral plate. Thus, further clinical investigations can be considered.