In order to investigate the tolerance mechanism and physiological response of plants under phenanthrene stress,foliar application experiment to soybean（Glycine max. L）was conducted,and the effects of different concentrations of phenanthrene to the growth of soybean seedlings,including phenotypic difference,biomass,oxidative damage and antioxidant enzyme activities,were explored. The results showed that the biomass of leaves increased under low concentration of phenanthrene stress（≤50 μmol/L）. Also the content of chlorophyll and carotenoid increased. The content malondialdehyde（MDA）,the activity of proline,superoxide dismutase（SOD）,and peroxidase（POD）were significantly higher than those in control group. Under the concentration of phenanthrene（75-100 μmol/L）,the content of MDA increased along with the increasing of phenanthrene concentration,while the biomass of the soybean seedlings,content of chlorophyll,the content of permeable stress substance,the activity of SOD were inhibited,and the carotenoid content and POD activity in the leaves were high. The above results reveal that plants eliminate the effects of applying phenanthrene in leaves on the biomass of the plants,content of chlorophyll,and oxidative stress by increasing POD and SOD activities as well as the contents of carotenoid and permeable stress substance. In addition,POD and carotenoid maintain high levels under high concentration of phenanthrene,suggesting that they play a more stable role in the corresponding phenanthrene stress.
Brassinosteroids（BRs）,a class of steroid hormones,play important roles in regulation of plant growth and development,as well as the response to stress. To date,the crosstalk between BR and mitochondria and signaling mechanism of BR in regulating mitochondria under stress remain largely unknown. In this study,the role of mitochondrial alternative respiratory pathway in BR inducing heat stress tolerance in Nicotiana benthamiana was investigated. External application of BR increased the resistance of N. benthamiana to heat stress,accompanied by the induction of alternative respiration and up-regulation of NbAOX1 expression. Chemical inhibition of alternative respiration or inhibition of NbAOX1 through virus-induced gene silencing assay compromised BR-induced heat resistance in N. benthamiana. In conclusion,our results indicate that the alternate respiratory pathway induced by BR can avoid the superfluous reactive oxygen species accumulation and protect the photosystems in plants under heat stress condition.
Plant resistance enhancement via activating plant immune system is one of the important approaches in green management system of plant diseases and pests. Mitogen activated protein kinase（MAPK）cascade is a vital signal transduction pathway in plant innate immune system. In order to investigate the molecular mechanism of Verticillium dahliae elicitor PevD1 inducing broad-spectrum disease resistance,transcriptome sequencing（RNA-seq）data from Nicotiana benthamiana response to PevD1 was obtained and a large number of differential gene expression（DGEs）were significantly enriched in the MAPK pathway. In this paper,DGEs enriched in the MAPK pathway were functionally classified and further analyzed. The involved functions by these DGEs were broad,including protein kinases（LRR- RLK）associated with plant recognition,ERF and WRKY transcription factor family for the regulation of gene expression,chitinase gene involved in disease resistance,calmodulin participated in calcium signaling,breathing outbreak oxidase（Rboh）regulating reactive oxygen species（ROS）and catalase（CAT）clearing ROS,etc. Expression patterns of 10 genes from the DGEs enriched in MAPK pathway were verified by qPCR and it was consistent with the RNA-Seq result. The antibody hybridization technique of specific phosphorylation sites was used to confirm that PevD1activated MAPK in N. benthamiana,i.e.,salicylic acid-induced protein kinase SIPK and wound-induced WIPK were activated by PevD1.
To screen the strain with good antagonistic effect against the phytophthora root rot of soybean,actinomycete XS1-5 with significant antagonism was isolated from soybean rhizosphere soil by agar block method and mycelia growth assay while taking the Phytophthora sojae of phytophthora root rot pathogen. Strain XS1-5 was identified as Streptomyces albosporeus based on morphological,physiochemical characters as well as molecular methods. The pot experiment was carried out with soybean seeds coated with different spore concentrations of the XS1-5. The results showed the application of the XS1-5 significantly promoted soybean growth,and increased chlorophyll content,root vitality and the protective enzymes in the leaf and root of soybean. When spore concentration was 1.0×10 8 CFU/g,the plant height,root length,fresh weight and dry weight increased by 19.92%、28.26%、87.40% and 34.51%;meanwhile,chlorophyll content（7.53 mg/L）by 50.6% and root vitality（685.41 μg/g·h）by 2.4 folds increased,compared with the control,respectively,as well as the CAT,SOD and POD activity of leaf increased significantly by 158.86%,459.71% and 135.45%. The above results indicate that the antagonistic strain XS1-5 screened in this study has a certain disease-control and growth-promoting effect on soybean.
To reveal the main salicylic acid（SA）biosynthetic pathway in Rhizoctonia solani-infected Zoysia japonica,the key genes was recognized with aligned homologous sequences,the responsive pathway was identified according to transcriptional profile during pathogenesis,SA concentration was measured,and phenylalanine ammonia lyase（PAL）activity was verified. As typical alleles of PAL,genes ZjPAL1-ZjPAL5 were up-regulated continuously in the diseased root shown by their corresponding Unigenes,meaning an active response to infection at transcription level. About genes encoding isochorismate synthase,only ZjICS1 transcripts were observed,whose abundance was always less than one-tenth of that of ZjPAL1-ZjPAL5 and tended downwards with infection increasing. The PAL activity in the root reduced after mycelial invasion into the endodermis of the root. The more the activity was weakening,the faster the decrease of synthesized SA concentration was. However,the SA concentration in the non-infected leaves remained high by enhanced PAL activity. Phenylalanine pathway regulated by PAL gene plays a major role in SA synthesis when Z. japonica is infected by R. solani. Responsive intensity increases with the infection deepening,and the reduction of PAL activity will result in SA concentration decreasing.
In order to investigate the differences of microRNAs（miRNAs）in growth and development of skeletal muscle between Wuzhishan and Landrace pigs and to explore the effects of differential miRNAs on post-transcriptional regulation of skeletal muscle development,we used the longissimus dorsi muscle of 8-month-old Wuzhishan pig and of Landrace pig to screen their differential miRNAs related to the development of skeletal muscle via Solexa sequencing combined with bioinformatics analysis. A total of 311 known porcine miRNAs were identified from 2 libraries,300 and 293 known miRNAs were identified in Wuzhishan and Landrace pigs respectively,and new identified miRNAs were 96 and 79 respectively. Fifteen of 17 screened differential miRNAs significantly down-regulated in the Landrace pig,while 2 miRNAs significantly up-regulated. A total of 574 target genes were predicted by the 17 differential miRNAs that enriched to 30 significantly different biological pathways（P<0.05）,of which 5 miRNAs enriched to the insulin signaling pathway（ssc-miR-362,ssc-miR-455-3p,ssc-miR-497,ssc-miR-499-5p,and ssc-miR-874）. This study reveals the differences in the growth and development of skeletal muscle between 8-month-old Wuzhishan pig and Landrace pig at the level of miRNA and provides basic data for further research on the molecular mechanism of skeletal muscle growth.
The aim of this study is to investigate the effects of gut microbiota on bile acid profile and bile acid metabolism in liver,jejunal contents and feces of pig models. Eleven piglets from aseptic caesarean section were randomly divided into germ-free（GF）group（5 piglets）and fecal microbiota transplantation（FMT）group（6 piglets）. GF group remained germ-free from beginning to end,and the FMT group was implanted with healthy porcine fecal bacteria at the age of 7 d. Liver,jejunal contents and fresh feces were collected for bile acid quantification at 42 d,as well as liver and jejunal tissues were collected for the quantification of genes related to bile acid metabolism. The results showed that：compared with the GF group,the total bile acid level in the piglet feces of the FMT group was significantly higher than that of the GF group（P<0.01）. The proportion of secondary bile acids in the jejunal contents and feces of the piglets in the FMT group to total bile acids was significantly higher than that in the GF group（P<0.05）,and the same trend was found in the liver（P<0.05）. Compared with the GF group,cholesterol 7-alpha hydroxy-lase gene（CYP7A1）,bile acid amino acid converting enzyme gene（BAT）,and farinol X receptor gene（FXR）,as well as genes related to bile acid synthesis and transport in the FMT group were down-regulated,while the expression of the intestinal transporter MRP2 gene was up-regulated. Thus,the transfer and colonization of gut microbiota can not only increase the bile acid excretion of piglets,increase the proportion of secondary bile acid,change the bile acid profile of piglets,but also affect the hepatointestinal circulation of bile acid.
Based on the high-density suspension culture of BHK-21 cells,this study is to optimize the serum-free medium in order to improve proliferation of the BHK-21 cells and amplification of foot-and-mouth virus（FMDV）. Firstly,the key nutrients in the serum-free medium were determined based on the metabolic characteristics and dynamics analysis of the BHK-21 cells. Then,the composition of the medium was optimized. Finally,the growth and FMDV-producing ability of the BHK-21 cells between before and after the optimization were compared and verified in bio-reactor. The maximum viable cell density reached 1.78×107 cells/mL during batch culturing of the BHK-21 cells in optimized serum-free medium（Opt-SFM）,and the situation of accumulating metabolic by-products was improved. Compared with non-optimized medium containing 1%（V/V）serum, TCID50 of the produced FMDV in the Opt-SFM showed a similar level at 7.25 lgTCID50/0.1 mL,while the yield of 146s particals increased by 50.7% to 15.6 g/mL. In conclusion,based on the requirements of cell growth and metabolic characteristics,optimizing nutrients and reducing metabolic by-products accumulation may effectively eliminate “cell density effect” and achieve ultra-high cell density and high yield of foot-and-mouth virus.
