Dietary bile acid supplementation in weaned piglets with intrauterine growth retardation improves colonic microbiota,metabolic activity,and epithelial function

Background Intrauterine growth retardation(IUGR)is one of the major constraints in animal production.Our previ-ous study showed that piglets with IUGR are associated with abnormal bile acid(BA)metabolism.This study explored whether dietary BA supplementation could improve growth performance and colonic development,function,micro-biota,and metabolites in the normal birth weight(NBW)and IUGR piglets.A total of 48 weaned piglets(24 IUGR and 24 NBW)were allocated to four groups(12 piglets per group):(i)NBW group,(ii)NBW+BA group,(iii)IUGR group,and(iv)IUGR+BA group.Samples were collected after 28 days of feeding.Results The results showed that dietary BA supplementation increased the length and weight of the colon and colon weight to body weight ratio,while decreased the plasma diamine oxidase(DAO)concentration in the NBW pig-lets(P<0.05).Dietary BA supplementation to IUGR piglets decreased(P<0.05)the plasma concentrations of D-lactate and endotoxin and colonic DAO and endotoxin,suggesting a beneficial effect on epithelial integrity.Moreover,dietary BA supplementation to NBW and IUGR piglets increased Firmicutes abundance and decreased Bacteroidetes abundance(P<0.05),whereas Lactobacillus was the dominant genus in the colon.Metabolome analysis revealed 65 and 51 differential metabolites in the colon of piglets fed a diet with/without BA,respectively,which was associated with the colonic function of IUGR piglets.Furthermore,dietary BA supplementation to IUGR piglets upregulated the expressions of CAT,GPX,SOD,Nrf1,IL-2,and IFN-γin colonic mucosa(P<0.05).Conclusions Collectively,dietary BA supplementation could improve the colonic function of IUGR piglets,which was associated with increasing proportions of potentially beneficial bacteria and metabolites.Furthermore,BA shows a promising application prospect in improving the intestinal ecosystem and health of animals.

Intrauterine growth retardation affects liver bile acid metabolism in growing pigs:effects associated with the changes of colonic bile acid derivatives

Background:Intrauterine growth retardation(IUGR)is associated with severely impaired nutrient metabolism and intestinal development of pigs.Our previous study found that IUGR altered intestinal microbiota and metabolites in the colon.However,the consequences of IUGR on bile acid metabolism in pigs remained unclear.The present study aimed to investigate the bile acid metabolism in the liver and the profile of bile acid derivatives in the colon of grow-ing pigs with IUGR using bile acid targeted metabolomics.Furthermore,we determined correlations between colonic microbiota composition and metabolites of IUGR and normal birth weight(NBW)pigs at different growth stages that were 7,21,and 28-day-old,and the average body weight(BW)of 25,50,and 100 kg of the NBW pigs.Results:The results showed that the plasma total bile acid concentration was higher(P<0.05)at the 25 kg BW stage and tended to increase(P=0.08)at 28-day-old in IUGR pigs.The hepatic gene expressions related to bile acid synthe-sis(CYP7A1,CYP27A1,and NTCP)were up-regulated(P<0.05),and the genes related to glucose and lipid metabolism(ATGL,HSL,and PC)were down-regulated(P<0.05)at the 25 kg BW stage in IUGR pigs when compared with the NBW group.Targeted metabolomics analysis showed that 29 bile acids and related compounds were detected in the colon of pigs.The colonic concentrations of dehydrolithocholic acid and apocholic acid were increased(P<0.05),while isodeoxycholic acid and 6,7-diketolithocholic acid were decreased(P<0.05)in IUGR pigs,when compared with the NBW pigs at the 25 kg BW stage.Moreover,Spearman’s correlation analysis revealed that colonic Unclassified_[Mogi-bacteriaceae],Lachnospira,and Slackia abundances were negatively correlated(P<0.05)with dehydrolithocholic acid,as well as the Unclassified_Clostridiaceae abundance with 6,7-diketolithocholic acid at the 25 kg BW stage.Conclusions:These findings suggest that IUGR could affect bile acid and glucolipid metabolism in growing pigs,especially at the 25 kg BW stage,these effects being paralleled by a modification of bile acid derivatives concentra-tions in the colonic content.The plausible links between these modified parameters are discussed.

母猪肠道微生态与繁殖生理研究进展

动物胃肠道微生物具有很强的代谢活性,对宿主的营养物质利用和生理代谢功能具有重要调控作用,可影响动物的生产性能和机体健康。为了适应胎儿的生长发育,妊娠期间母体的肠道菌群组成和代谢活性发生显著变化。笔者结合自己近年来的研究成果,对国内外母猪肠道微生态与繁殖生理方面取得的研究进展进行综述,以期为研发提高母猪繁殖性能的调控技术提供思路。

Effects of dietary protein/energy ratio on growth performance,carcass trait,meat quality,and plasma metabolites in pigs of different genotypes

Background： The protein/energy ratio is important for the production performance and utilization of available feed resources by animals. Increased protein consumption by mammals leads to elevated feed costs and increased nitrogen release into the environment. This study aimed to evaluate the effects of dietary protein/energy ratio on the growth performance, carcass traits, meat quality, and plasma metabolites of pigs of different genotypes. Methods： Bama mini-pigs and Landrace pigs were randomly assigned to two dietary treatment groups （Chinese conventional diet with low protein/energy ratio or National Research Council diet with high protein/energy ratio; n = 24 per treatment） in a 2 x 2 factorial arrangement. Blood and muscle samples were collected at the end of the nursery, growing, and finishing phases. Results： We observed significant interactions （P 〈 0.05） between breed and diet for total fat percentage, intramuscular fat （IMF） content, protein content in biceps femoris （BF） muscle, and plasma urea nitrogen （UN） concentration in the nursery phase; for average daily gain （ADG）, average daily feed intake （ADFI）, dry matter, IMF content in psoas major （PM） muscle, and plasma total protein and albumin concentrations in the growing phase; and for drip loss and plasma UN concentration in the finishing phase. Breed influenced （P 〈 0.05） growth performance, carcass traits, and meat quality, but not plasma metabolites. Throughout the trial, Landrace pigs showed significantly higher （P 〈 0.0_5） ADG, ADFI, dressing percentage, lean mass rate, and loin-eye area than did Bama mini-pigs, but significantly lower （P 〈 0.0.5） feed/gain ratio, fat percentage, backfat thickness, and IMF content. Dietary protein/energy ratio influenced the pH value, chemical composition of BF and PM muscles, and plasma activities of glutamic-pyruvic transaminase and gamma-glutamyl transpeptidase, and plasma concentration of UN. Conclusions： Compared with Landrace pigs, Bama mini-pigs showed slower growth and lower carcass performance, but had better meat quality. Moreover, unlike Landrace pigs, the dietary protein/energy ratio did not affect the growth performance of Bama mini-pigs. These results suggest that, in swine production, low dietary protein/energy ratio may be useful for reducing feed costs and minimizing the adverse effects of ammonia release into the environment.

Dietary proline supplementation alters colonic luminal microbiota and bacterial metabolite composition between days 45 and 70 of pregnancy in Huanjiang mini-pigs

Background: Pregnancy is associated with important changes in gut microbiota composition. Dietary factors may affect the diversity, composition, and metabolic activity of the intestinal microbiota. Among amino acids, proline is known to play important roles in protein metabolism and structure, cell differentiation, conceptus growth and development, and gut microbiota re-equilibration in case of dysbiosis.Results: Dietary supplementation with 1% proline decreased(P < 0.05) the amounts of Klebsiella pneumoniae,Peptostreptococcus productus, Pseudomonas, and Veillonella spp. in distal colonic contents than that in the control group. The colonic contents of Butyrivibrio fibrisolvens, Bifidobacterium sp., Clostridium coccoides, Clostridium coccoides-Eubacterium rectale, Clostridium leptum subgroup, Escherichia coli, Faecalibacterium prausnitzii,Fusobacterium prausnitzii, and Prevotella increased(P < 0.05) on d 70 of pregnancy as compared with those on d 45 of pregnancy. The colonic concentrations of acetate, total straight-chain fatty acid, and total short-chain fatty acids(SCFA) in the proline-supplemented group were lower(P < 0.05), and butyrate level(P = 0.06) decreased as compared with the control group. Almost all of the SCFA displayed higher(P < 0.05) concentrations in proximal colonic contents on d 70 of pregnancy than those on d 45 of pregnancy. The concentrations of 1,7-heptyl diamine(P = 0.09) and phenylethylamine(P < 0.05) in proximal colonic contents were higher, while those of spermidine(P = 0.05) and total bioamine(P = 0.06) tended to be lower in the proline-supplemented group than those in the control group. The concentrations of spermidine, spermine, and total bioamine in colonic contents were higher(P < 0.05) on d 70 of pregnancy than those measured on d 45 of pregnancy. In contrast, the concentration of phenylethylamine was lower(P < 0.05) on d 70 than on d 45 of pregnancy.(Continued on next page)(Continued from previous page)Conclusion: These findings indicate that L-proline supplementation modifies both the colonic microbiota composition and the luminal concentrations of several bacterial metabolites. Furthermore, our data show that both the microbiota composition and the concentrations of bacterial metabolites are evolving in the course of pregnancy. These results are discussed in terms of possible implication in terms of luminal environment and consequences for gut physiology and health.

Intrauterine growth restriction alters growth performance, plasma hormones,and small intestinal microbial communities in growing-finishing pigs

Background: The interaction of the gut microbiota with key metabolic and physiological processes may be associated with poor growth outcomes in animals born with intrauterine growth restriction(IUGR).Results: Growth performance, plasma hormone concentrations, and intestinal microbiota composition were analyzed in IUGR pigs and in normal birth weight(NBW) pigs when the NBW pigs reached 25, 50, and 100 kg of body weight(BW). Compared to NBW pigs, IUGR pigs had lower initial, weaned, and final BW, and lower average daily gain and average daily feed intake in all the considered time points. In the 25 kg BW group, IUGR pigs had higher concentrations of plasma ghrelin and pancreatic polypeptide(PP), but lower insulin concentration than NBW pigs, while the situation was reversed in the 50 kg BW group. As compared to NBW pigs, IUGR pigs had higher microbial alpha diversity in the jejunum and ileum;in the 50 and 100 kg BW groups, IUGR pigs had higher Firmicutes abundance but lower Proteobacteria abundance in the jejunum, and lower Lactobacillus abundance in the jejunum and ileum;in the 25 kg BW group, IUGR pigs showed higher unclassified Ruminococcaceae abundance in the ileum;and in 25 and 50 kg BW groups, IUGR pigs showed lower Ochrobactrum abundance in the jejunum.Spearman's correlation revealed that Lactobacillus was negatively correlated with growth performance, while unclassified Ruminococcaceae was positively correlated. Predictive metagenomic analysis detected significantly different expression of genes in the intestinal microbiota between IUGR and NBW pigs, suggesting different metabolic capabilities between the two groups.Conclusions: Growing-finishing IUGR pigs showed lower growth performance, higher microbial alpha diversity, and differences in plasma hormone concentrations compared to NBW pigs. Alterations in the abundance of Firmicutes,Proteobacteria, Ruminococcaceae, Lactobacillus, and Ochrobactrum in the small intestine may be associated with IUGR, and may therefore serve as a future target for gut microbiota intervention in growing-finishing IUGR pigs.

Effects of dietary protein restriction on muscle fiber characteristics and m TORC1 pathway in the skeletal muscle of growing-finishing pigs

Background： To investigate the effects of dietary crude protein（CP） restriction on muscle fiber characteristics and key regulators related to protein deposition in skeletal muscle, a total of 18 growing-finishing pigs（62.30 ± 0.88 kg）were allotted to 3 groups and fed with the recommended adequate protein（AP, 16 % CP） diet, moderately restricted protein（MP, 13 % CP） diet and low protein（LP, 10 % CP） diet, respectively. The skeletal muscle of different locations in pigs, including longissimus dorsi muscle（LDM）, psoas major muscle（PMM） and biceps femoris muscle（BFM） were collected and analyzed.Results： Results showed that growing-finishing pigs fed the MP or AP diet improved（P 〈 0.01） the average daily gain and feed： gain ratio compared with those fed the LP diet, and the MP diet tended to increase（P = 0.09） the weight of LDM. Moreover, the ATP content and energy charge value were varied among muscle samples from different locations of pigs fed the reduced protein diets. We also observed that pigs fed the MP diet up-regulated（P 〈 0.05） muscular m RNA expression of all the selected key genes, except that myosin heavy chain（My HC） IIb,My HC IIx, while m RNA expression of ubiquitin ligases genes was not affected by dietary CP level. Additionally, the activation of mammalian target of rapamycin complex 1（m TORC1） pathway was stimulated（P 〈 0.05） in skeletal muscle of the pigs fed the MP or AP diet compared with those fed the LP diet.Conclusion： The results suggest that the pigs fed the MP diet could catch up to the growth performance and the LDM weight of the pigs fed the AP diet, and the underlying mechanism may be partly due to the alteration in energy status, modulation of muscle fiber characteristics and m TORC1 activation as well as its downstream effectors in skeletal muscle of different locations in growing-finishing pigs.

Developmental changes in intercellular junctions and Kv channels in the intestine of piglets during the suckling and post-weaning periods

Background： The intestinal epithelium is an important barrier that depends on a complex mixture of proteins and these proteins comprise different intercellular junctions. The purpose of this study was to investigate the postnatal and developmental changes in morphology, intercellular junctions and voltage-gated potassium（Kv） channels in the intestine of piglets during the suckling and post-weaning periods.Results： Samples of the small intestine were obtained from 1-, 7-, 14-, and 21-d-old suckling piglets and piglets on d 1, 3, 5, and 7 after weaning at 14 d of age. The results showed that the percentage of proliferating cell nuclear antigen（PCNA）-positive cells and alkaline phosphatase（AKP） activity, as well as the abundances of E-cadherin,occludin, and Kv1.5 m RNA and claudin-1, claudin-3, and occludin protein in the jejunum were increased from d 1to d 21 during the suckling period（P 〈 0.05）. Weaning induced decreases in the percentage of PCNA-positive cells,AKP activity and the abundances of E-cadherin, occludin and zonula occludens（ZO）-1 m RNA or protein in the jejunum on d 1, 3 and 5 post-weaning（P 〈 0.05）. There were lower abundances of E-cadherin, occludin and ZO-1m RNA as well as claudin-1, claudin-3 and ZO-1 protein in the jejunum of weanling piglets than in 21-d-old suckling piglets（P 〈 0.05）. The abundances of E-cadherin, occludin, ZO-1 and integrin m RNA were positively related to the percentage of PCNA-positive cells.Conclusion： Weaning at 14 d of age induced damage to the intestinal morphology and barrier. While there was an adaptive restoration on d 7 post-weaning, the measured values did not return to the pre-weaning levels, which reflected the impairment of intercellular junctions and Kv channels.

Development of small intestinal barrier function and underlying mechanism in Chinese indigenous and Duroc piglets during suckling and weaning periods

This study explored the developmental changes in small intestinal barrier function and the potential regulatory roles of intestinal microbiota and metabolites in different breeds of piglets during suckling and weaning periods.Taoyuan black(TB),Xiangcun black(XB),and Duroc(DR)piglets(10 litters per breed;half male and half female)were selected for sampling to evaluate the intestinal barrier-related indexes and intestinal microbiota and metabolites at 1,10,21(weaned),and 24(3 d after weaning)d old.The results showed that weaning led to severe shedding of small intestinal microvilli and sparse microvilli arrangement.D-lactate level in the ileum of TB and XB piglets during suckling and weaning periods was lower(P<0.01)than that of DR piglets,as well as the ileal diamine oxidase level at 1 d old.The expression level of mucin 1 was higher(P<0.05)in the ileum of TB and XB piglets than that of DR piglets,and it was the highest in the ileum of TB piglets at 21 d old.The expression levels of mucin 2 and mucin 13 were higher(P<0.10)in TB and XB piglets than those of DR piglets at 21 d old,whereas mucin2 and mucin 13 in the ileum of TB and XB piglets were higher(P<0.05)than those of DR piglets at 24 d old.TB and XB piglets had a lower relative abundance of Escherichia_Shigella at 21 and 24 d old,but they had higher Streptococcus at 1 and 24 d old than DR piglets(P<0.01).Differential metabolites between the three breeds of piglets were mainly related to oxidative phosphorylation,steroid biosynthesis,and bile acid synthesis.Collectively,these findings suggest that different pig breeds present differences in the development of the small intestinal barrier function.Compared with DR piglets,TB and XB piglets had higher intestinal permeability during the suckling period and a stronger intestinal mechanical barrier after weaning.Moreover,intestinal microbiota and metabolites are the key factors for developing small intestinal barrier functions in different breeds of piglets.

enOsCas12f1-mediated exon skipping for Duchenne muscular dystrophy therapy in humanized mouse model

Duchenne muscular dystrophy(DMD)is a severe neuromuscular disorder caused by mutations in the dystrophin gene,which encodes the essential protein dystrophin.This genetic condition,affecting approximately 1 in 5000 male births worldwide(Birnkrant et al.,2018),is characterized by progressive muscle weakness and wasting,leading to premature death in the second or third decade of life(Farini et al.,2016).The absence of dystrophin protein causes instability in the sarcolemma,which predisposes individuals to myonecrosis and activation of inflammatory signaling cascades.Unfortunately,there is currently no effective cure for DMD,and glucocorticoid steroids are commonly used in clinical settings to delay symptom development(Merlini et al.,2003).

An engineered xCas12i with high activity,high specificity,and broad PAM range

Dear Editor,The clustered regularly interspaced short palindromic repeats-Cas(CRISPR-Cas)systems,including type II Cas9 and type V Cas12 systems,which serve in the adaptive immunity of prokaryotes against viruses,have been developed into genome-editing tools(Anzalone et al.,2020;Doudna,2020).Compared with type II systems,the type V systems including V-A to V-K showed more functional diversity(Yan et al.,2019).Amongst them,Cas12i has a relatively smaller size(1,033-1,093 aa),compared to SpCas9 and Cas12a,and has a 5'-TTN protospacer adjacent motif(PAM)preference(Yan et al.,2019).

Phosphogypsum stabilization of bauxite residue:Conversion of its alkaline characteristics

Reduction of the high alkalinity of bauxite residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, phosphogypsum, a waste product from the phosphate fertilizer industry, was used to drive the alkaline transformation of the bauxite residue. Under optimal water washing conditions(liquid/solid ratio of 2 mL/g, 30°C, 24 hr), the impact of quantity added, reaction time and reaction mechanism during phosphogypsum application were investigated. Phosphogypsum addition effectively lowered p H levels and reduced the soluble alkalinity by 92.2%. It was found that the concentration of soluble Na and Ca ions in the supernatant increased gradually, whilst the exchangeable Na+and Ca^(2+)in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca^(2+)became the dominant element in the solid phase(phosphogypsum addition of 2%, liquid/solid ratio of 2 mL/g, 30°C, 12 hr). X-ray diffraction data indicated that cancrinite and hydrogarnet were the primary alkaline minerals. SEM images suggested that phosphogypsum could promote the formation of stable macroaggregates, whilst the content of Ca^(2+)increased from 5.6% to 18.2% and Na reduced from 6.8% to 2.4%. Treatment with phosphogypsum could significantly promote the transformation of alkalinity cations by neutralization, precipitation and replacement reactions.This research provided a feasible method to promote soil formation of bauxite residue by phosphogypsum amendment.

Autophagy and tight junction proteins in the intestine and intestinal diseases

The intestinal epithelium(IE) forms an indispensible barrier and interface between the intestinal interstitium and the luminal environment. The IE regulates water, ion and nutrient transport while providing a barrier against toxins, pathogens(bacteria, fungi and virus) and antigens. The apical intercellular tight junctions(TJ) are responsible for the paracellular barrier function and regulate transepithelial flux of ions and solutes between adjacent cells. Increased intestinal permeability caused by defects in the IE TJ barrier is considered an important pathogenic factor for the development of intestinal inflammation, diarrhea and malnutrition in humans and animals. In fact, defects in the IE TJ barrier allow increased antigenic penetration, resulting in an amplified inflammatory response in inflammatory bowel disease(IBD), necrotizing enterocolitis and ischemia-reperfusion injury. Conversely, the beneficial enhancement of the intestinal TJ barrier has been shown to resolve intestinal inflammation and apoptosis in both animal models of IBD and human IBD. Autophagy(self-eating mechanism) is an intracellular lysosome-dependent degradation and recycling pathway essential for cell survival and homeostasis.Dysregulated autophagy has been shown to be directly associated with many pathological processes,including IBD. Importantly, the crosstalk between IE TJ and autophagy has been revealed recently. We showed that autophagy enhanced IE TJ barrier function by increasing transepithelial resistance and reducing the paracellular permeability of small solutes and ions, which is, in part, by targeting claudin-2,a cation-selective, pore-forming, transmembrane TJ protein, for lysosome(autophagy)-mediated degradation. Interestingly, previous studies have shown that the inflamed intestinal mucosa in patients with active IBD has increased claudin-2 expression. In addition, inflammatory cytokines(for example,tumor necrosis factor-α, interleukin-6, interleukin-13, and interleukin-17) whose levels are increased in IBD patients cause an increase in claudin-2 expression and a claudin-2-dependent increase in TJ permeability. Thus, the role of claudin-2 in intestinal pathological processes has been attributed, in part, to the increase of intestinal TJ permeability. Claudin-2 represents a new therapeutic target in treating IBD,diarrhea and malnutrition in animals and humans.

Serine-to-glycine ratios in low-protein diets regulate intramuscular fat by affecting lipid metabolism and myofiber type transition in the skeletal muscle of growing-finishing pigs

Serine and glycine are 2 of the first-affected nonessential amino acids in low crude protein(CP)diets for pigs.Therefore,we explored the effects of different dietary serine-to-glycine ratios on growth perfor-mance and lipid metabolism in growing-finishing pigs.A total of 160 crossbred healthy barrows,with a similar body weight of around 59.50 kg,were randomly allotted into 1 of 5 treatments(8 pens per treatment and 4 pigs per pen).The serine-to-glycine ratios of the 5 dietary treatments were as follows:diet A(NORMAL group),1.18∶1(16%CP);diet B(LOW group),1.2∶1(12%CP);diet C(S2G1 group),2∶1(12%CP);diet D(S1G2 group),1∶2(12%CP);and diet E(S1G1 group),1∶1(12%CP).We found that the pigs fed a low CP diet(12%CP),when maintaining serine-to-glycine ratio at 1∶2 and a total amount of 1.44%,had the same average daily gain as the pigs fed a normal CP diet(16%CP)(P>0.05),but they had increased intramuscular fat(P<0.05).Furthermore,they exhibited higher expression of genes involved in lipid oxidation(P<0.05),which was regulated by modulating methylation levels in the promoters of acyl-CoA oxidase 1(ACOX1)and acyl-CoA dehydrogenase medium chain(ACADM).When compared with the pigs fed a normal CP diet,these pigs had more oxidative myofibers(P<0.05),which were regulated by AMPK-PGC-1αand Calcineurin-MEF2/NFAT pathways in a coordinated manner.Our findings suggested that a dietary serine-to-glycine ratio of 1:2 is beneficial for improving meat quality in pigs fed a low CP diet.

Dietary supplementation with betaine or glycine improves the carcass trait,meat quality and lipid metabolism of finishing mini-pigs

The objective of the study is to evaluate and compare the effects of betaine or glycine on carcass trait,meat quality and lipid metabolism of finishing Huan Jiang mini-pigs.Betaine called trimethylglycine is a methyl derivative of glycine,but few researches were conducted to compare the impact of dietary betaine and glycine on pigs.One hundred and forty-four Huan Jiang mini-pigs(body weight=10.55±0.15 kg;70 d)were randomly divided to 3 treatment groups(basal diet,glycine or betaine).Results indicated that dietary betaine increased the average daily gain(ADG)and final weight(P<0.05).Dietary glycine or betaine markedly reduced average backfat thickness(P<0.05)and heightened lean percentage(P<0.01)compared to the control group.Moreover,in comparison with the control group,betaine significantly improved the redness(a*)and tenderness(shear force)of the longissimus dorsi(LD)muscle(P<0.05),whereas glycine only raised the value of a*of the LD muscle(P<0.05).These results showed that diet supplemented with 0.25%betaine and equimolar amounts of glycine could regulate cascass trait and meat quality of finishing Huan Jiang mini-pigs,and the effect of betaine was superior to that of glycine.

SIZ1-Mediated SUMOylation of ROS1 Enhances Its Stability and Positively Regulates Active DNA Demethylation in Arabidopsis

The 5-methylcytosine DNA glycosylase/lyase REPRESSOR OF SILENCING 1(ROS1)-mediated active DNA demethylation is critical for shaping the genomic DNA methylation landscape in Arabidopsis.Whether and how the stability of ROS1 may be regulated by post-translational modifications is unknown.Using a methylation-sensitive PCR(CHOP-PCR)-based forward genetic screen forArabidopsis DNA hyper-methyl-ation mutants,we identified the SUMO E3 ligase SIZ1 as a critical regulator of active DNA demethylation.Dysfunction of SIZ1 leads to hyper-methylation at approximately 1000 genomic regions.SIZ1 physically in-teracts with ROS1 and mediates the SUMOylation of ROS1.The SUMOylation of ROS1 is reduced in siz1 mutant plants.Compared with that in wild-type plants,the protein level of ROS1 is significantly decreased,whereas there is an increased level of ROS1 transcripts in siz1 mutant plants.Our results suggest that SIZ1-mediated SUMOylation of ROS1 promotes its stability and positively regulates active DNA demethylation.

Regulatory role of L-proline in fetal pig growth and intestinal epithelial cell proliferation

L-proline(Pro)is a precursor of ornithine,which is converted into polyamines via ornithine decarboxylase(ODC).Polyamines plays a key role in the proliferation of intestinal epithelial cells.The study investigated the effect of Pro on polyamine metabolism and cell proliferation on porcine enterocytes in vivo and in vitro.Twenty-four Huanjiang mini-pigs were randomly assigned into 1 of 3 groups and fed a basal diet that contained 0.77%alanine(Ala,iso-nitrogenous control),1%Pro or 1%Pro+0.0167%α-difluoromethylornithine(DFMO)from d 15 to 70 of gestation.The fetal body weight and number of fetuses per litter were determined,and the small and large intestines were obtained on d 70±1.78 of gestation.The in vitro study was performed in intestinal porcine epithelial(IPEC-J2)cells cultured in Dulbecco’s modified Eagle medium-high glucose(DMEM-H)containing 0μmol/L Pro,400μmol/L Pro,or400μmol/L Pro+10 mmol/L DFMO for 4 d.The results showed that maternal dietary supplementation with 1%Pro increased fetal weight;the protein and DNA concentrations of the fetal small intestine;and mRNA levels for potassium voltage-gated channel,shaker-related subfamily,member 1(Kv1.1)in the fetal small and large intestines(P<0.05).Supplementing Pro to either gilts or IPEC-J2 cells increased ODC protein abundances and polyamine concentrations in the fetal intestines and IPEC-J2 cells(P<0.05).In comparison with the Pro group,the combined administration of Pro and DFMO reduced the expression of ODC protein and spermine concentration in the fetal intestine,as well as the concentrations of putrescine,spermidine and spermine in IPEC-J2 cells(P<0.05).Meanwhile,the percentage of cells in the S-phase and the mRNA levels of proto-oncogenes c-fos and c-myc were increased in response to Pro supplementation,whereas depletion of cellular polyamines with DFMO increased tumor protein p53(p53)mRNA levels(P<0.05).Taken together,dietary supplementation with Pro improved fetal pig growth and intestinal epithelial cell proliferation via enhancing polyamine synthesis.

Precise genome editing without exogenous donor DNA via retron editing system in human cells

Dear Editor,CRISPR-Cas9 mediated seamless genome editing can be achieved by incorporating donor DNA into the CRISPR-Cas9 target loci via homology-directed repair(HDR),albeit with relative low efficiency due to the inefficient delivery of exogenous DNA(Cox et al.,2015;Gao,2021).Retrons are bacterial phage-defense related operons composed of a specialized reverse transcriptase(RT)and a relevant non-coding RNA(ncRNA)which can be partially reverse tran-scribed by RT initiating at a conserved guanosine(G)residue to produce a multicopy single-stranded DNA(msDNA)(Yee et al.,1984;Millman et al.,2020).After being reverse transcribed,the msDNA is usually covalently teth-ered to the ncRNA through the 2',5'-phosphodiesterbond between the priming G in ncRNA and 5'end of msDNA(Dhundale et al.,1987).The reverse transcription process,of which the specialized RT recognizes the unique secondary structure of retron ncRNA,is highly specific(Hsu et al.,1989).Additionally,desired msDNA can be generated in vivo by replacing the dispensable region of retron ncRNA with desired sequences(Mirochnitchenko et al.,1994;Simon et al.,2019).Therefore,retrons are promising biological sources for in vivo generation of DNA donors for HDR-me-diated precise genome editing.

Myokine interleukin-15 expression profile is different in suckling and weaning piglets

Interleukin-15(IL-15) is a cytokine highly expressed in skeletal muscle. The objective of the present study was to investigate the development of muscle IL-15 expression in suckling piglets and in early weaning piglets(day 14) at each level, that is, mRNA, protein, and secretion. Eight litters(eight piglets per litter) of newborn healthy piglets(Large × White × Landrace) with a similar initial weight(1618.0 ± 140.1 g) were chosen and divided into two groups, Group one used suckling piglets that were killed, respectively, at days 1,7,14,21, and group two used early(day 14) weaning piglets that were killed respectively, at days 15, 17, 19, 21. In group one, IL-15 gene expression levels increased significantly(P < 0.05) along with increased body weight over time. IL-15 protein expression levels in piglets at day 21 of age were higher(P < 0.05) than those in piglets at other ages, and there was no difference(P > 0.05)among piglets at other ages. These findings indicated that increased IL-15 mRNA expression did not result in a corresponding increase of its protein expression. In group two, which used early weaning piglets from days 15-19, IL-15 mRNA and protein expression levels increased constantly(P < 0.05) and were higher(P < 0.05) than those in suckling piglets. Moreover, there was no gain of body weight(P > 0.05) compared with suckling piglets at day 14 of age. However, IL-15 protein expression levels in early weaning piglets at day 21 of age dropped significantly(P < 0.05) to the levels as suckling piglets at day 21 of age, while body weight increased(P < 0.05) markedly to the levels as suckling piglets at day 21 of age. In both groups, the serum IL-15 levels of piglets decreased significantly(P < 0.01) over time. Taken together, our results indicate that IL-15 expression differs in suckling piglets and in weaning piglets. It is speculated that IL-15 may play an important role in counteracting the effects of early weaning stress.

Protein security and food security in China

Food security,the need to meet nutritional requirements,and four main problems for food protein security in China are analyzed.From the perspective of residents’nutritional requirements and balanced dietary patterns,the conclusion is that food security in China is in essence dependent on protein production and security of supply and that fat and carbohydrates supply in China can reach self-sufficiency.Considering the situation of food protein production and consumption in China,policy suggestions are made,which could ensure a balanced supply and demand for food protein and food security in China.