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Background Polyploidy has often been considered to confer plants a better adaptation to environmental stresses. Tetraploid citrus rootstocks are expected to have stronger stress tolerance than diploid. Plenty of doubled diploid citrus plants were exploited from diploid species for citrus rootstock improvement. However, limited metabolic and molecular information related to tetraploidization is currently available at a systemic biological level. This study aimed to evaluate the occurrence and extent of metabolic and transcriptional changes induced by tetraploidization in Ziyang xiangcheng ( Citrus junos Sieb. ex Tanaka), which is a special citrus germplasm native to China and widely used as an iron deficiency tolerant citrus rootstock. Results Doubled diploid Ziyang xiangcheng has typical morphological and anatomical features such as shorter plant height, larger and thicker leaves, bigger stomata and lower stomatal density, compared to its diploid parent. GC-MS (Gas chromatography coupled to mass spectrometry) analysis revealed that tetraploidization has an activation effect on the accumulation of primary metabolites in leaves; many stress-related metabolites such as sucrose, proline and γ-aminobutyric acid (GABA) was remarkably up-regulated in doubled diploid. However, LC-QTOF-MS (Liquid chromatography quadrupole time-of-flight mass spectrometry) analysis demonstrated that tetraploidization has an inhibition effect on the accumulation of secondary metabolites in leaves; all the 33 flavones were down-regulated while all the 6 flavanones were up-regulated in 4x. By RNA-seq analysis, only 212 genes (0.8% of detected genes) are found significantly differentially expressed between 2x and 4x leaves. Notably, those genes were highly related to stress-response functions, including responses to salt stress, water and abscisic acid. Interestingly, the transcriptional divergence could not explain the metabolic changes, probably due to post-transcriptional regulation. Conclusion Taken together, tetraploidization induced considerable changes in leaf primary and secondary metabolite accumulation in Ziyang xiangcheng. However, the effect of tetraploidization on transcriptome is limited. Compared to diploid, higher expression level of stress related genes and higher content of stress related metabolites in doubled diploid could be beneficial for its stress tolerance.

Numerous studies indicated the physical benefits of regular exercise, but the neurophysiological mechanisms of regular exercise in elders were less investigated. We aimed to compare changes in brain activity during exercise in elderly people and in young adults with and without regular exercise habits. A total of 36 healthy young adults (M/F:18/18) and 35 healthy elderly adults (M/F:20/15) participated in this study. According to exercise habits, each age group were classified into regular and occasional exerciser groups. ECG, EEG, and EMG signals were recorded using V-AMP with a 1-kHz sampling rate. The participants were instructed to perform three 5-min bicycle rides with different exercise loads. The EEG spectral power of elders who exercised regularly revealed the strongest positive correlation with their exercise intensity by using Pearson correlation analysis. The results demonstrate that exercise-induced significant cortical activation in the elderly participants who exercised regularly, and most of the p-values are less than 0.001. No significant correlation was observed between spectral power and exercise intensity in the elders who exercised occasionally. The young participants who exercised regularly had greater cardiac and neurobiological efficiency. Our results may provide a new exercise therapy reference for adult groups with different exercise habits, especially for the elders.

Compared to other energy sources, nuclear reactors offer several advantages as a spacecraft power source, including compact size, high power density, and long operating life. These qualities make nuclear power an ideal energy source for future deep space exploration. A whole system model of the space nuclear reactor consisting of the reactor neutron kinetics, reactivity control, reactor heat transfer, heat exchanger, and thermoelectric converter was developed. In addition, an electrical power control system was designed based on the developed dynamic model. The GRS method was used to quantitatively calculate the uncertainty of coupling parameters of the neutronics, thermal-hydraulics, and control system for the space reactor. The Spearman correlation coefficient was applied in the sensitivity analysis of system input parameters to output parameters. The calculation results showed that the uncertainty of the output parameters caused by coupling parameters had the most considerable variation, with a relative standard deviation < 2.01%. Effective delayed neutron fraction was most sensitive to electrical power. To obtain optimal control performance, the non-dominated sorting genetic algorithm method was employed to optimize the controller parameters based on the uncertainty quantification calculation. Two typical transient simulations were conducted to test the adaptive ability of the optimized controller in the uncertainty dynamic system, including 100% full power (FP) to 90% FP step load reduction transient and 5% FP/min linear variable load transient. The results showed that, considering the influence of system uncertainty, the optimized controller could improve the response speed and load following accuracy of electrical power control, in which the effectiveness and superiority have been verified.

KEY MESSAGE : 2 n megagametophyte formation plays an important role in polyploidization in polyembryonic citrus and is valuable for plant improvement. Tetraploid plants are frequently observed in the seedlings of diploid polyembryonic citrus genotypes. However, the mechanisms underlying the formation of tetraploids are still indistinct when apomictic citrus genotypes are used as female parent to cross with tetraploids. Herein, 54 tetraploid progenies, which were unexpectedly obtained previously from four 2x × 4x crosses using polyembryonic ‘Nadorcott’ tangor as seed parent, were analyzed by 22 simple sequence repeat (SSR) markers, aiming to reveal their genetic origin and the mechanism underlying 2n megagametophyte formation. The results showed that 13 tetraploids from all these four crosses were doubled diploids as indicated by their identical SSR allelic profile with their female parent; while the remaining 41 tetraploids apparently exhibited paternally derived alleles, which confirmed their zygotic origin. Furthermore, the genotyping of all hybrids indicated that all of them arose from 2n megagametophytes. Based on the genotypes of 2n megagametophytes, the analysis of maternal heterozygosity restitution (HR) for each marker showed that it varied from 0.00 to 87.80 % with a mean value of 40.89 %. In addition, it was observed that 13 markers displayed a lower rate than 50 %. On the basis of the above results, it can be speculated that the second division restitution (SDR) is the mechanism underlying the 2n megagametophyte formation in ‘Nadorcott’ tangor. The elucidation of the mechanism of 2n megagametophyte formation will be of great help to optimize further sexual hybridization for polyploids in citrus.

Citrus allotetraploid somatic hybrids obtained via protoplast fusion have been employed as pollen/seed parents in interploidy crosses to produce triploid plants aiming to develop seedless citrus. However, their meiotic behavior, which directs the parental heterozygosity transmission, has been rarely explored. In this study, the meiotic inheritance pattern was evaluated in a citrus allotetraploid somatic hybrid between ‘Nova’ tangelo and ‘HB’ (Hirado Buntan) pummelo through cytogenetic observation of meiosis and segregation analysis using 18 simple sequence repeat (SSR) markers. Meiotic analysis of pollen mother cells (PMCs) showed a high rate of quadrivalents (31.6 %) in this allotetraploid although bivalents were predominant (57.6 %). For segregation analysis, the meiotic chromosome-pairing behavior was analyzed by genotyping a triploid population derived from a cross between diploid ‘Nadorcott’ tangor and this allotetraploid using the microsatellite DNA allele counting-peak ratios (MAC-PR) method, from which the genotypes of diploid male gametes were inferred. In agreement with the expectation of cytogenetic analysis, a mixture of diploid, tetraploid, and intermediated inheritance patterns was deduced due to the co-existence of preferential, non-preferential, and intermediate pairing models among all analyzed loci. Parental heterozygosity transmission was further analyzed among 14 loci where each chromosome in the allotetraploid could be clearly tracked. It showed that the mean value of 23.8 % intra-parental and 76.2 % inter-parental heterozygosity was transmitted. The preferential pairing pattern at the loci displaying an intermediate inheritance pattern was also discussed.

Visualization of specific genomic loci in live cells is a prerequisite for the investigation of dynamic changes in chro- matin architecture during diverse biological processes, such as cellular aging. However, current precision genomic imaging methods are hampered by the lack of fluorescent probes with high specificity and signal-to-noise contrast. We find that conventional transcription activator-like effectors （TALEs） tend to form protein aggregates, thereby compromising their performance in imaging applications. Through screening, we found that fusing thioredoxin with TALEs prevented aggregate formation, unlocking the full power of TALE-based genomic imaging. Using thioredoxin-fused TALEs （TTALEs）, we achieved high-quality imaging at various genomic loci and observed aging-associated （epi） genomic alterations at telomeres and centromeres in human and mouse premature aging models. Importantly, we identified attrition of ribosomal DNA repeats as a molecular marker for human aging. Our study establishes a simple and robust imaging method for precisely monitoring chromatin dynamics in vitro and in vivo.

This study focuses on the role of amino acids in xylem sap of tomato grown in hydroponics in a medium supplemented with a series of concentration of La and Y. Eighteen amino acids in xylem saps were identified and measured by reversed-phase high-performance liquid chromatography. The main amino acids in xylem sap samples of the tomato are histidine, tryptophan, aspartic acid, and glutamic acid. The concentration of glutamic acid in xylem sap significantly increased in the La and Y treatment compared to the control. By analyzing the correlation between concentrations of amino acids and concentrations of La and Y in the xylem saps, we considered that the glutamic acid in xylem saps seemed to participate in the long-distance La and Y translocation processes, and histidine did not relate to xylem La and Y transport of tomato. The role of other amino acids which was excreted by tomato has not been demonstrated in the long-distance transport of La and Y in the xylem.

Compared to other energy sources, nuclear reactors offer several advantages as a spacecraft power source, including compact size, high power density, and long operating life. These qualities make nuclear power an ideal energy source for future deep space exploration. A whole system model of the space nuclear reactor consisting of the reactor neutron kinetics, reactivity control, reactor heat transfer, heat exchanger, and thermoelectric converter was developed. In addition, an electrical power control system was designed based on the developed dynamic model. The GRS method was used to quantitatively calculate the uncertainty of coupling parameters of the neutronics, thermal-hydraulics, and control system for the space reactor. The Spearman correlation coefficient was applied in the sensitivity analysis of system input parameters to output parameters. The calculation results showed that the uncertainty of the output parameters caused by coupling parameters had the most considerable variation, with a relative standard deviation < 2.01%. Effective delayed neutron fraction was most sensitive to electrical power. To obtain optimal control performance, the non-dominated sorting genetic algorithm method was employed to optimize the controller parameters based on the uncertainty quantification calculation. Two typical transient simulations were conducted to test the adaptive ability of the optimized controller in the uncertainty dynamic system, including 100% full power (FP) to 90% FP step load reduction transient and 5% FP/min linear variable load transient. The results showed that, considering the influence of system uncertainty, the optimized controller could improve the response speed and load following accuracy of electrical power control, in which the effectiveness and superiority have been verified.

Aim： To investigate the relationship between Ureaplasma urealyticum （UU） infection and semen quality. Methods： From 2001 to 2003, 346 eligible patients aged 20-45 years were invited from two hospitals in Shanghai, China, to participate in an investigation which included questionnaires about general and reproductive health, an external genital tract examination, UU culture and semen analysis. Multiple linear regression models were used to examine whether UU had a significant effect on semen quality after adjustment for confounding factors. Results： Findings suggested that UU infection was associated with higher semen viscosity and lower semen pH value. Sperm concentration was lower in UU positive subjects than that in UU negative subjects （54.04 × 10^6/mL vs.70.58 × 10^6/mL）. However, UU did not significantly affect other semen quality indexes. Conclusion： UU infection of the male genital tract could negatively influence semen quality.

Seafood products has a long history and the teachings ‘Raw crabs and shrimp live’ spread among people. This study carrys out an investigation into parasitic infections of raw seafood of Qinhuangdao through sampling, smearing, UV examination and statistical methods. The experimental datas we get tell that there is various kinds of parasite lar-vae in body of shrimp frequently and metacercariae in crabs. The seafood likeoster and clam aren't without parasites also. Experiments show that the lung fl-uke metacercaria could live about 48 hours in Salt solution with concentration-f 10%, 43 hours in 15% liquor and 28 hours in 14 degrees of yellow wine. Itis obvious that these parasites could not killed through salt leaching and temul-entia. Due to domestic waters pollution is serious, so don't eat raw food.