Minimal nutritional requirements for immobilized yeast

The effect of reduced nutritional levels (particularly nitrogen source) for immobilized K. fragilis type yeast were studied using a trickle flow, "differential" plug flow type reactor with cells immobilized by adsorption onto an absorbant packing matrix. Minimizing nutrient levels in a feed stream to an immobilized cell reactor (ICR) might have the benefits of reducing cell growth and clogging problems in the ICR, reducing feed preparation costs, as well as reducing effluent disposal costs. In this study step changes in test feed medium nutrient compositions were introduced to the ICR, followed by a return to a basal medium. Gas evolution rates were monitored and logged on a continuous basis, and effluent cell density was used as an indicator of cell growth rate of the immobilized cell mass. Startup of the reactor using a YEP medium showed a rapid buildup of cells in the reactor during the initial 110 h operation. The population density then stabilized at 1.6 x 10(11) cells/g sponge. A defined medium containing a complex mix of essential nutrients with an inorganic nitrogen source (ammonium sulfate) was able to maintain 90% of the productivity in the ICR as compared to the YEP medium, but proved unable to promote growth of the immobilized cell mass during startup. Experiments on reduced ammonium sulfate in the defined medium, and reduced yeast extract and peptone in YEP medium indicated that stable productivity could be maintained for extended periods (80 h) in the complete absence of any nutrients besides a few salts (potassium phosphate and magnesium sulfate). It was found that productivity rates dropped by 35-65% from maximal values as nitrogenous nutrients were eliminated from the test mediums, while growth rates (as determined by shed cell density from the reactor) dropped by 75-95%. Thus, nutritional deficiencies largely decoupled growth and productivity of the immobilized yeast which suggests productivity is both growth- and non-growth-associated for the immobilized cells. A yeast extract concentration of 0.375 g/L with or without 1 g/L ammonium sulfate was determined to be the minimum level which gave a sustained increase in productivity rates as compared to the nutritionally deficient salt medium. This represents a 94% reduction in complex nitrogenous nutrient levels compared to standard YEP batch medium (3 g/L YE and 3.5 g/L peptone).     

Metabolism of Cytokinin : DEPHOSPHORYLATION OF CYTOKININ RIBONUCLEOTIDE BY 5'-NUCLEOTIDASES FROM WHEAT GERM CYTOSOL

Two forms (F-I and F-II) of 5′-nucleotidases (5′-ribonucleotide phosphohydrolase, EC 3.1.3.5) which catalyze the dephosphorylation of N⁶-(Δ²-isopentenyl)adenosine 5′-monophosphate and AMP to form the corresponding nucleosides were partially purified from the cytosol of wheat (Triticum aestivum) germ. Both the F-I (molecular weight, 57,000) and F-II (molecular weight, 110,000) 5′-nucleotidases dephosphorylate the ribonucleotides at an optimum pH of 7. The K_m values for the cytokinin nucleotide are 3.5 micromolar (F-I enzyme) and 12.8 micromolar (F-II enzyme) in 100 millimolar Tris-maleate buffer (pH 7) at 37 C. The F-I enzyme is less rapidly inactivated by heating than is the F-II enzyme. Both nucleotidases hydrolyze purine ribonucleoside 5′-phosphates, AMP being the preferred substrate. N⁶-(Δ²-isopentenyl)Adenosine 5′-monophosphate is hydrolyzed at a rate 72 and 86% that of AMP by the F-I and F-II nucleotides, respectively. Phenylphosphate and 3′-AMP are not substrates for the enzymes. It is proposed that dephosphorylation of cytokinin nucleotide by cytosol 5′-nucleotidases may play an important role in regulating levels of “active cytokinin” in plant cells.     

Adrenocorticotropin administration during early gestation on conceptus development in swine

The purpose of this study was to examine the effect of exogenous adrenocorticotropin (ACTH), administered to gilts during early stages of gestation, upon fetal survival and various maternal and conceptus parameters. Forty-eight gilts of approximately 6-7 months of age were bred by means of artificial insemination after detection of the second estrus and randomly allotted to one of 12 treatment-period groups. Treatment consisted of a daily intramuscular injection of 0, 40 or 80 U.S.P. units of a long acting ACTH preparation for a period of five days. The injection periods were 1-5, 6-10, 11-15 or 16-20 days of gestation with day one corresponding to 48 hours post-estrus detection. All gilts were slaughtered at approximately 37 days of gestation. Forty-two of the 48 inseminated gilts conceived. Conception rate was not different (P>.10) among the 12 treatment-period combinations. Percent fetal survival was greater (P<.09) in gilts receiving 80 U.S.P. units of ACTH (82 +/- 4.3%; X +/- SEM ) than in gilts receiving 40 U.S.P. units of ACTH (68.8 +/- 4.5%). The percent fetal survival in the control group (71.7 +/- 3.9%) was not different (P>.10) from either of the two ACTH treatment groups. A significant (P<.05) treatment by period interaction for percent fetal survival was observed. The lowest percent fetal survival (48.0 +/- 9.0%) was observed in gilts receiving 40 U.S.P. units of ACTH on day 11-15 of gestation. No significant (P>.10) differences were detected among the 12 treatment-period combinations for any of the maternal or conceptus parameters measured.     

Selective Modulation of RNA Polymerase I Activity during Growth Transitions in the Soybean Seedling

RNA polymerase I and II activities were measured in tissues of the soybean (Glycina max, var. Wayne) hypocotyl where dramatic changes in the relative level of RNA synthesis are associated with normal and auxin-induced growth transitions. When assayed in isolated nuclei, the activity of RNA polymerase I changed much more than the activity of RNA polymerase II during these growth transitions. The activity of RNA polymerase I expressed in the nuclei generally showed a positive correlation with the relative level of RNA synthesis (i.e. accumulation) of that tissue. Following solubilization of the RNA polymerases from these isolated nuclei and fractionation of them on DEAE-cellulose, the activity of RNA polymerase I relative to that of RNA polymerase II showed smaller changes during these growth transitions than when assayed in the nuclei. Thus, these data indicate that the activity of RNA polymerase I is significantly modulated in the nucleus, up or down depending upon the growth state, during growth transitions in the soybean in addition to lesser changes which occur in the apparent level of the enzyme.     

Effect of leaf water deficit on stomatal and nonstomatal regulation of net carbon dioxide assimilation

The effect of leaf water deficit on net CO₂ assimilation was studied under two conditions: in one, the stomata were allowed to contribute to the regulation of CO₂ assimilation; in the other, air was forced through the leaf at a constant rate to overcome the effects of change in stomatal resistance accompanying changes in leaf water deficit. When the stomata were allowed to regulate the gaseous diffusive resistance of the leaf, CO₂ assimilation decreased with increasing leaf water deficit. However, when air was forced through the leaf, the rate of assimilation was not inhibited by increasing leaf water deficit. The results indicate that the inhibition of net CO₂ assimilation with increasing leaf water deficit is a consequence of an increase in the diffusive resistance to gas exchange and not of a change in apparent mesophyll resistance.     

Defining endogenous barcoding sites for CRISPR/Cas9-based cell lineage tracing in zebrafish

There is a growing interest in developing experimental methods for tracking the developmental cell lineages of a complex organism.The recently developed CRISPR/Cas9-based barcoding method is,although highly promising,difficult to scale up because it relies on exogenous barcoding sequences that are engineered into the genome.In this study,we characterized 78 high-quality endogenous sites in the zebrafish genome that can be used as CRISPR/Cas9-based barcoding sites.The 78 sites are all highly expressed in most of the cell types according to single-cell RNA sequencing(scRNA-seq)data.Hence,the barcoding information of the 78 endogenous sites is recovered by the available scRNA-seq platforms,enabling simultaneous characterization of cell type and cell lineage information.     

The RHD variants in Chinese population

The Rhesus (Rh) blood group system is the most important blood group system in hemolytic disease of the fetus and newborn (HDFN). In clinical transfusions, the D antigen in the Rh blood group system comes third, behind antigens A and B which from ABO blood group system. Over the past decade, molecular technologies have been used to investigate the RHD allele in different ethnic groups. This review first introduces the basic structure of RhD protein and coding genes, then focuses on D-negative, weak D, partial D, DEL, RhD_null variants reported in the Chinese population. To date, more than 460 RHD variants have been reported around the world, but less than 70 RHD variants have been reported in the Chinese population. Further research is needed to identify more RHD polymorphism and establish criteria for blood detection and transfusion guidelines for RHD variants. Only in this way can we better guarantee the safety of blood transfusion and prevent the occurrence of HDFN. With the accumulation of research and clinical data, we should be clearer which RHD variants are to be regarded as RhD negative and which need to be regarded as RhD positive.     

Potassium and phosphorus transport and signaling in plants

Nitrogen(N), potassium(K), and phosphorus(P) are essential macronutrients for plant growth and development, and their availability affects crop yield. Compared with N, the relatively low availability of K and P in soils limits crop production and thus threatens food security and agricultural sustainability. Improvement of plant nutrient utilization efficiency provides a potential route to overcome the effects of K and P deficiencies. Investigation of the molecular mechanisms underlying how plants sense, absorb, transport, and use K and P is an important prerequisite to improve crop nutrient utilization efficiency. In this review, we summarize current understanding of K and P transport and signaling in plants, mainly taking Arabidopsis thaliana and rice(Oryza sativa) as examples. We also discuss the mechanisms coordinating transport of N and K, as well as P and N.     

Protein kinases in plant responses to drought,salt, and cold stress

Protein kinases are major players in various signal transduction pathways. Understanding the molecular mechanisms behind plant responses to biotic and abiotic stresses has become critical for developing and breeding climate-resilient crops. In this review,we summarize recent progress on understanding plant drought, salt, and cold stress responses, with a focus on signal perception and transduction by different protein kinases, especially sucrose nonfermenting1(SNF1)-related protein kinases(Sn RKs),mitogen-activated protein kinase(MAPK) cascades,calcium-dependent protein kinases(CDPKs/CPKs),and receptor-like kinases(RLKs). We also discuss future challenges in these research fields.     

A practical guide to amplicon and metagenomic analysis of microbiome data

Advances in high-throughput sequencing(HTS)have fostered rapid developments in the field of microbiome research,and massive microbiome datasets are now being generated.However,the diversity of software tools and the complexity of analysis pipelines make it difficult to access this field.Here,we systematically summarize the advantages and limitations of micro-biome methods.Then,we recommend specific pipelines for amplicon and metagenomic analyses,and describe commonly-used software and databases,to help researchers select the appropriate tools.Furthermore,we introduce statistical and visualization methods suit-able for microbiome analysis,including alpha-and beta-diversity,taxonomic composition,difference compar-isons,correlation,networks,machine learning,evolu-tion,source tracing,and common visualization styles to help researchers make informed choices.Finally,a step-by-step reproducible analysis guide is introduced.We hope this review will allow researchers to carry out data analysis more effectively and to quickly select the appropriate tools in order to efficiently mine the bio-logical significance behind the data.