Cotton miR319b-Targeted TCP4-Like Enhances Plant Defense Against Verticillium dahliae by Activating GhICS1 Transcription Expression

Teosinte branched1/Cincinnata/proliferating cell factor (TCP) transcription factors play important roles in plant growth and defense. However, the molecular mechanisms of TCPs participating in plant defense remain unclear. Here, we characterized a cotton TCP4-like fine-tuned by miR319b, which could interact with NON-EXPRESSER OF PATHOGEN-RELATED GENES 1 (NPR1) to directly activate isochorismate synthase 1 (ICS1) expression, facilitating plant resistance against Verticillium dahliae. mRNA degradome data and GUS-fused assay showed that GhTCP4-like mRNA was directedly cleaved by ghr-miR319b. Knockdown of ghr-miR319b increased plant resistance to V. dahliae, whereas silencing GhTCP4-like increased plant susceptibility by the virus-induced gene silencing (VIGS) method, suggesting that GhTCP4-like is a positive regulator of plant defense. According to the electrophoretic mobility shift assay and GUS reporter analysis, GhTCP4-like could transcriptionally activate GhICS1 expression, resulting in increased salicylic acid (SA) accumulation. Yeast two-hybrid and luciferase complementation image analyses demonstrated that GhTCP4-like interacts with GhNPR1, which can promote GhTCP4-like transcriptional activation in GhICS1 expression according to the GUS reporter assay. Together, these results revealed that GhTCP4-like interacts with GhNPR1 to promote GhICS1 expression through fine-tuning of ghr-miR319b, leading to SA accumulation, which is percepted by NPR1 to increase plant defense against V. dahliae. Therefore, GhTCP4-like participates in a positive feedback regulation loop of SA biosynthesis via NPR1, increasing plant defenses against fungal infection.

The Cotton miR477-CBP60A Module Participates in Plant Defense Against Verticillium dahlia

Previous reports have shown that, when Verticillium dahliae localizes at the root surface, many microRNAs (miRNAs) were identified at the early induction stage. Here, we constructed two groups from two timepoints of small RNA (sRNA) in cotton root responses to V. dahliae at the later induction stage, pathogen localizing in the interior of root tissue. We identified 71 known and 378 novel miRNAs from six libraries of the pathogen-induced and the control sRNAs. Combined with degradome and sRNA sequencing, 178 corresponding miRNA target genes were identified, in which 40 target genes from differentially expressed miRNAs were primarily associated with oxidation-reduction and stress responses. More importantly, we characterized the cotton miR477-CBP60A module in the later response of the plant to V. dahliae infection. A β-glucuronidase fusion reporter and cleavage site analysis showed that ghr-miR477 directly cleaved the messenger RNA of GhCBP60A in the posttranscriptional process. The ghr-miR477-silencing decreased plant resistance to this fungus, while the knockdown of GhCBP60A increased plant resistance, which regulated GhICS1 expression to determine salicylic acid level. Our data documented that numerous later-inducible miRNAs in the plant response to V. dahliae, suggesting that these miRNAs play important roles in plant resistance to vascular disease.

Enhanced degradation of perfluorooctanoic acid by a genome shuffling-modified Pseudomonas parafulva YAB-1

Perfluorooctanoic acid (PFOA) as an emerging persistent organic pollutant is hard to be degraded by conventional methods because of its stable physical and chemical properties. Microbial transformation is an attractive remediation approach to prevent and clean up PFOA contamination. To date, several strains of wild microbes have been reported to have limited capacity to degrade PFOA, selection of superior strains degrading PFOA become urgently necessary. Here, we report the application of genome shuffling to improve the PFOA-degrading bacterium Pseudomonas Parafulva YAB-1. The initial mutant populations of strain YAB1 were generated by nitrosoguanidine and ultraviolet irradiation mutagenesis respectively, resulting in mutants YM-9 and YM-19 with slightly improved PFOA-degrading ability. YM-9 and YM-19 were used as the starting strains for three rounds of recursive protoplast fusion. The positive mutants were screened on inorganic salt medium plates containing different concentrations of PFOA and selected based on their PFOA degradability in shake-flask fermentation test. The best performing recombinant F3-52 was isolated after three rounds of genome shuffling. In batch fermentation, the PFOA degradation rate of mutant F3-52 was up to 58.6%, which was 1.8-fold higher than that of the parent strain YAB1, and 1.6-fold higher than the initial mutants YM-9 and YM-19. Pass-generation test indicated that the heredity character of F3-52 was stable. The results demonstrated that genome shuffling was an efficient method for improving PFOA degradation of Pseudomonas Parafulva YAB1. The bred mutant F3-52 with 58.6% PFOA-degrading rate could be used for the environmental control of PFOA pollutant.

Cotton WATs Modulate SA Biosynthesis and Local Lignin Deposition Participating in Plant Resistance Against Verticillium dahliae

Verticillium wilt, caused by Verticillium dahliae, seriously limits cotton production. It is difficult to control this pathogen damage mainly due to the complexity of the molecular mechanism of plant resistance to V. dahliae. Here, we identified three homologous cotton Walls Are Thin (WAT) genes, which were designated as GhWAT1, GhWAT2, and GhWAT3. The GhWATs were predominantly expressed in the roots, internodes, and hypocotyls and induced by infection with V. dahliae and treatment with indole-3-acetic acid (IAA) and salicylic acid (SA). GhWAT1-, GhWAT2-, or GhWAT3-silenced plants showed a comparable phenotype and level of resistance with control plants, but simultaneously silenced three GhWATs (GhWAT123-silenced), inhibited plant growth and increased plant resistance to V. dahliae, indicating that these genes were functionally redundant. In the GhWAT123-silenced plants, the expression of SA related genes was significantly upregulated compared with the control, resulting in an increase of SA level. Moreover, the histochemical analysis showed that xylem development was inhibited in GhWAT123-silenced plants compared with the control. However, lignin deposition increased in the xylem of the GhWAT123-silenced plants compared to the control, and there were higher expression levels of lignin synthesis- and lignifications-related genes in the GhWAT123-silenced plants. Collectively, the results showed that GhWATs in triple-silenced plants acts as negative regulators of plant resistance against V. dahliae. The potential mechanism of the WATs functioning in the plant defence can modulate the SA biosynthesis and lignin deposition in the xylem.

Molecular Cloning and Functional Characterization of a Dihydroflavonol 4-Reductase from Vitis bellula

Vitis bellula is a new grape crop in southern China. Berries of this species are rich in antioxidative anthocyanins and proanthocyanidins. This study reports cloning and functional characterization of a cDNA encoding a V. bellula dihydroflavonol reductase (VbDFR) involved in the biosynthesis of anthocyanins and proanthocyanidins. A cDNA including 1014 bp was cloned from young leaves and its open reading frame (ORF) was deduced encoding 337 amino acids, highly similar to V. vinifera DFR (VvDFR). Green florescence protein fusion and confocal microscopy analysis determined the cytosolic localization of VbDFR in plant cells. A soluble recombinant VbDFR was induced and purified from E. coli for enzyme assay. In the presence of NADPH, the recombinant enzyme catalyzed dihydrokaempferol (DHK) and dihydroquercetin (DHQ) to their corresponding leucoanthocyanidins. The VbDFR cDNA was introduced into tobacco plants via Agrobacterium-mediated transformation. The overexpression of VbDFR increased anthocyanin production in flowers. Anthocyanin hydrolysis and chromatographic analysis revealed that transgenic flowers produced pelargonidin and delphinidin, which were not detected in control flowers. These data demonstrated that the overexpression of VbDFR produced new tobacco anthocyanidins. In summary, all data demonstrate that VbDFR is a useful gene to provide three types of substrates for metabolic engineering of anthocyanins and proanthocyanidins in grape crops and other crops.

Isolation, identification, and degradation performance of a PFOA-degrading strain

The perfluorooctanoic acid (PFOA)-degrading strain YAB1 was isolated from the soil near a perfluorinated compound production plant through acclimation and enrichment culture, using PFOA as the sole carbon source. This strain was preliminarily identified as Pseudomonas parafulva based on colony morphology, physiological and biochemical features, and 16S rRNA gene sequencing. Using shaking flask fermentation, the maximum tolerable concentration of YAB1 on PFOA was found to be 1000 mg/L. The optimal conditions for bacterial growth and PFOA degradation were 30°C, pH 7, 2% inoculum, and an initial PFOA concentration of 500 mg/L. After 96 h of culture, the PFOA degradation rate determined by GC-MS analysis was 32.4%. When 1 g/L glucose was added to the inorganic salt culture medium, the degradation rate increased to 48.1%. Glucose was the best exogenous carbon source for the degradation of PFOA. This study reports the degradation performance of PFOA-degrading bacteria.

Isolation, identification, and degradation performance of a PFOA-degrading strain

The perfluorooctanoic acid (PFOA)-degrading strain YAB1 was isolated from the soil near a perfluorinated compound production plant through acclimation and enrichment culture, using PFOA as the sole carbon source. This strain was preliminarily identified as Pseudomonas parafulva based on colony morphology, physiological and biochemical features, and 16S rRNA gene sequencing. Using shaking flask fermentation, the maximum tolerable concentration of YAB1 on PFOA was found to be 1000 mg/L. The optimal conditions for bacterial growth and PFOA degradation were 30°C, pH 7, 2% inoculum, and an initial PFOA concentration of 500 mg/L. After 96 h of culture, the PFOA degradation rate determined by GC-MS analysis was 32.4%. When 1 g/L glucose was added to the inorganic salt culture medium, the degradation rate increased to 48.1%. Glucose was the best exogenous carbon source for the degradation of PFOA. This study reports the degradation performance of PFOA-degrading bacteria.

Functional characterization of an anthocyanidin reductase gene from the fibers of upland cotton (Gossypium hirsutum)

Metabolic profiling, gene cloning, enzymatic analysis, ectopic expression, and gene silencing experiments demonstrate that the anthocyanidin reductase (ANR) pathway is involved in the biosynthesis of proanthocyanidins in upland cotton. Proanthocyanidins (PAs) are oligomeric or polymeric flavan-3-ols, however, the biosynthetic pathway of PAs in cotton remains to be elucidated. Here, we report on an anthocyanidin reductase (ANR) gene from cotton fibers and the ANR pathway of PAs. Phytochemical analysis demonstrated that leaves, stems, roots, and early developing fibers produced PAs and their monomers, including (-)-epicatechin, (-)-catechin, (-)-epigallocatechin, and (-)-gallocatechin. Crude PA extractions from different tissues were boiled in Butanol:HCl. Cyanidin, delphinidin, and pelargonidin were produced, indicating that cotton PAs include diverse extension unit structures. An ANR cDNA homolog (named GhANR1) was cloned from developing fibers. The open reading frame, composed of 1,011 bp nucleotides, was expressed in E. coli to obtain a recombinant protein. In the presence of NADPH, the recombinant enzyme catalyzed cyanidin, delphinidin, and pelargonidin to (-)-epicatechin and (-)-catechin, (-)-epigallocatechin and (-)-gallocatechin, and (-)-epiafzelechin and (-)-afzelechin, respectively. The ectopic expression of GhANR11 in an Arabidopsis ban mutant allowed for the reconstruction of the ANR pathway and PA biosynthesis in the seed coat. Virus-induced gene silencing (VIGS) of GhANR11 led to a significant increase in anthocyanins and a decrease in the PAs, (-)-epicatechin, and (-)-catechin in the stems and leaves of VIGS-infected plants. Taken together, these data demonstrate that the ANR pathway contributes to the biosynthesis of flavan-3-ols and PAs in cotton.

Preparation and immunogenicity-evaluation of typhoid O-specific polysaccharides bio-conjugate vaccines

Typhoid fever caused by Salmonella Typhi is still a major public health problem in developing countries. In this study, we constructed a genetically modified Salmonella Typhi strain expressing O-specific polysaccharides (OPS) antigen conjugated to a carrier, recombinant Pseudomonas aeruginosa exotoxin A(rEPA N29). The conjugates (OPS-rEPA N29) were further purified and evaluated for their immunogenicity. The results of ELISA showed that the conjugates evoked higher titers of IgG than OPS, suggesting that rEPAN29 increased immunogenicity of OPS significantly as a carrier. Moreover, three injections with 3-week interval evoked slightly higher titers of IgG than three injections with 2-week interval. However, injection of excess conjugates could not evoke higher titers of IgG against lipid polysaccharide (LPS). In summary, our study provides a new strategy for preparing polysaccharides-protein conjugate vaccines as well as similar bio-conjugate vaccines of other Gram-negative pathogens.

[Cloning, prokaryotic expression and characterization of lysine decarboxylase gene from Huperzia serrata]

Huperzine A is a promising drug to treat Alzheimer's disease (AD). To date, its biosynthetic pathway is still unknown. Lysine decarboxylase (LDC) has been proposed to catalyze the first-step of the biosynthesis of huperzine A. To identify and characterize LDCs from Huperzia serrata, we isolated two LDC fragments (LDC1 and LDC2) from leaves of H. serrata by RT-PCR and then cloned them into pMD 19-T vector. Sequence analysis showed that LDC1 and LDC2 genes shared 95.3% identity and encoded the protein of 212 and 202 amino acid residues respectively. Thus, we ligated LDC genes into pET-32a(+) to obtain recombinant expressing vectors pET-32a(+)/LDC1 and pET-32a(+)/LDC2 respectively. We further introduced two expression vectors into Escherichia coli BL21(DE3) and cultured positive colonies of E. coli in liquid LB medium. After inducing for 4 hours with 260 μg/mL IPTG at 30 degrees C, soluble recombinant Trx-LDC1 and Trx-LDC2 were obtained and isolated for purification using a Ni-NTA affinity chromatography. We incubated purified recombinant proteins with L-lysine in the enzyme reaction buffer at 37 degrees C and then derived the reaction products using dansyl chloride. It was found that both Trx-LDC1 and Trx-LDC2 had decarboxylase activity, could convert L-lysine into cadaverine by way of thin layer chromatography assay. Further, bioinformatics analysis indicated that deduced LDC1 and LDC2 had different physicochemical properties, but similar secondary and three-dimensional structures.

[Diversity of halophilic and halotolerant bacteria isolated from non-saline soil collected from Xiaoxi National Natural Reserve, Hunan Province]

OBJECTIVE

To investigate the diversity of cultivable halophilic and halotolerant bacteria isolated from ordinary non-saline soil samples collected from Xiaoxi National Natural Reserve (28 degrees 42' 15"-28 degrees 53' 15" N, 110 degrees 6' 50"-110 degrees 21' 35" E), Hunan Province, China.

METHODS

Bacterial strains were isolated from the samples by using the conventional culture-dependent method and investigated by using phylogenetic analysis based on 16S rRNA gene sequence comparisons.

RESULTS

We isolated 114 bacterial strains (8 moderately halophilic, 19 slightly halophilic, 87 halotolerant) from the samples on media (marine agar 2216, International Streptomyces Project medium 2 and 5, nutrient and humic acid agars) supplemented with 5% to 20% (w/v) NaCl. On the basis of morphological, physiological and biochemical characteristics, we selected 61 strains to perform a phylogenetic analysis based on 16S rRNA gene sequences. Results showed that 61 isolates represented 41 species, belonging to 18 genera (Actinomadura, Arthrobacter, Bacillus, Brachybacterium, Brevibacterium, Erwinia, Halobacillus, Jeotgalibacillus, Microbacterium, Microbulbifer, Nocardia, Pseudomonas, Rheinheimera, Rhodococcus, Sphingomonas, Staphylococcus, Streptomyces, Yaniella) of 16 families ( Alteromonadaceae, Bacillaceae, Brevibacteriaceae, Chromatiaceae, Dermabacteraceae, Enterobacteriaceae, Microbacteriaceae, Micrococcaceae, Nocardiaceae, Planococcaceae, Pseudomonadaceae, Sphingomonadaceae, Staphylococcaceae, Streptomycetaceae, Thermomonosporaceae, Yaniellaceae) in three phyla (Actinobacteria, Firmicutes, Proteobacteria). The most abundant and diverse isolates were within the phylum Firmicutes (38 strains; 62.3%) and the phylum Actinobacteria (18 strains; 29.5%). The phylogenetic distance matrix results suggested that there were obvious genetic divergences between most isolates and their closestly related type strains (16S rRNA gene sequence similarities ranged from 96.9% to 99.8%), and that, out of 61 isolates, at least 7 strains (JSM 070026, JSM 081004, JSM 081006, JSM 081008, JSM 083058, JSM 083085, JSM 084035) should represent 7 potential novel species within 6 characterized genera (Yaniella, Bacillus, Jeotgalibacillus, Sphingomonas, Rheinheimera, Microbulbifer).

CONCLUSION

The results presented here showed that there is abundant diversity of halophilic and halotolerant bacteria, as well as a number of novel species in non-saline soil collected from Xiaoxi National Natural Reserve, Hunan Province, China.

[Cross-protective effect of the Cp39 adhesive proteins against avian Pasteurella multicida in mice]

OBJECTIVE

We evaluated the cross-protective effect of a 39-kDa adhesive protein (Cp39), recombinant adhesive protein (rCp39), and capsular proteins from in vitro and in vivo grown avian P. multocida in mice.

METHODS

The Cp39 was purified by electroelution from capsular proteins of in vivo grown strain C48-3. The rCp39 was expressed in E. coli B21 as a soluble protein by IPTG inducing, and purified with pMAL protein fusion and purification system. Mice of each group were subcutaneously immunized twice with 100 microg of rCp39, Cp39 or capsular proteins from in vivo or in vitro grown strain C48-3 with in complete or incomplete Freund adjuvant at 2-week intervals. Five mice of each group were challenged with 100 LD50 of avian P. multocida strain C48-3 or rabbit P. multocida strain C51-3 two weeks after the second immunization, while the antibody response specific for rCp39 was determined by ELISA.

RESULTS

SDS-PAGE indicated that the Cp39 protein was expressed in vitro and in vivo grown P. multocida. Mice immunized with rCp39, native Cp39 or capsular proteins from in vivo and in vitro grown strain C48-3 were protected completely against the challenge with the homologous strain C48-3, while 60 - 80% protection was demonstrated in the mice against the challenge with the heterologous strain C51-3.

CONCLUSION

In conclusion, rCp39 is a cross immunoprotective antigen of P. multocida capsular serogroup A strains, and might be a useful vaccine candidate against fowl cholera.

[Immunity of native SpaA and recombinant SpaA-N against Erysipelothrix rhusiopathiae infection in mice]

OBJECTIVE

We evaluated the effects of surface protective antigen A (SpaA) and its N-teminal protective domain (rSpaA-N) against Erysipelothrix rhusiopathiae infection in mice.

METHODS

The SpaA was purified by electroelution from NaOH-extracted antigen of Erysipelothrix rhusiopathiae strain C43311. The rSpaA-N was expressed in E. coli BL21 as a soluble protein by IPTG inducing, and purified with GST affinity chromatography. Mice of each group were subcutaneously immunized three times with 50 microg or 100 microg of native SpaA, rSpaA-N or NaOH-extracted antigen with in complete or incomplete Freund adjuvant at 2-week intervals. Five mice of each group were challenged with 100 LD50 of Erysipelothrix rhusiopathiae virulent strain C43065 two weeks after the third immunization, and the specific antibody responses for SpaA was determined by indirect ELISA.

RESULTS

Mice immunized with 50 microg or 100 microg of native SpaA, rSpaA-N, or NaOH-extracted antigen were protected completely against the challenge with strain C43065. There was no significant difference (P < 0.05) between the antibody responses observed for native SpaA, rSpaA-N and NaOH-extracted antigen at any dosages. Western blot results indicated that the native SpaA and rSpaA-N were recognized specifically by an antiserum against the native SpaA of strain C43311.

CONCLUSION

These results demonstrated that the rSpaA-N is a protective antigen of Erysipelothrix rhusiopathiae serotype 2 strains, and might be a useful vaccine candidate against swine erysipelas.

[Diversity of culturable bacteria associated with the sea urchin Hemicentrotus pulcherrimus from Naozhou Island]

OBJECTIVE

To investigate the diversity of culturable bacteria isolated from the sea urchin Hemicentrotus pulcherrimus collected from a tidal flat of Naozhou Island (20 degrees 52'N - 20 degrees 56'N 110 degrees 33'E - 110 degrees 38'E), Leizhou Bay, South China Sea, China.

METHODS

Bacteria were isolated from the sample by using conventional culture-dependent method and then investigated by using phylogenetic analysis based on 16S rRNA gene sequence comparisons.

RESULTS

We isolated 106 bacterial strains from the sample on media (Difco marine 2216, International Streotomyces Project medium 2, nutrient, sea water and humic acid agars) supplemented with 0 - 2 mol/L NaCl. On the basis of morphological, physiological and biochemical characteristics, we selected 34 strains to perform a phylogenetic analysis based on 16S rRNA gene sequences. Our results showed that 34 isolates represented 21 species, belonging to 17 genera (Alteromonas, Bacillus, Brachybacterium, Brevibacterium, Halobacillus, Halomonas, Nocardiopsis, Oceanobacillus, Piscibacillus, Planococcus, Pontibacillus, Pseudoalteromonas, Pseudonocardia, Salinicoccus, Salinivibrio, Staphylococcus, Vibrio, Virgibacillus) of 10 families (Alteromonadaceae, Bacillaceae, Brevibacteriaceae, Dermabacteraceae, Halomonadaceae, Planococcaceae, Pseudoalteromonadaceae, Pseudonocardiaceae, Nocardiopsaceae, Staphylococcaceae, Vibrionaceae) in three phylogenetic groups (Actinobacteria, Firmicutes, Gamma-Proteobacteria). The most abundant and diverse isolates were within the phylum Firmicutes (58.8%) and the subphylum Gamma-Proteobacteria (26.5%). The phylogenetic distance matrix results suggested that there were obvious genetic divergences between most isolates and their closestly related type strains (16S rRNA gene sequence similarities ranged from 99.6 to 99.9%), and that, out of 34 isolates, at least 5 strains (JSM 076033, JSM 076056, JSM 076093, JSM 078063, JSM 078169) could represent 5 potential new species within 5 characterized genera (Jeotgalicoccus, Pontibacillus, Halomonas, Bacillus, Sporosarcina), in which the descriptions of 3 novel species [Jeotgalicoccus marinus (type strain, JSM 076033), Pontibacillus halophilus (JSM 076056), Halomonas zhanjiangensis (JSM 078169)] have been published in IJSEM (International Journal of Systematic and Evolutionary Microbiology).

CONCLUSION

The results presented above showed that there are abundant bacteria diversity in the sea urchin Hemicentrotus pulcherrimus collected from Naozhou Island.

[Studies on bioconversion conditions and stereoselectivity of Arthrobacter K1108 hydantoinase]

The bioconversion conditions of hydantoinase of Arthrobacter K1108 were studied. It was shown that the optimum temperature of the enzyme is 55 degrees C, and the optimum pH is 7.0. The enzyme can be activated by Co2+ and Fe2+, while inhibited by Ca2+. The optimal substrate of the hydantoinase is 5-benzylhydantoin, while 5-phenylhydantoin and 5-indolylmethylhydantoin cannot effectively digested, showing a high specificity on the substrates. An investigation on the hydantoinase stereoselectivity mechanism showed that the N-carbamoylamino acid hydrolase is stereoselective but the hydantoin hydrolase is not.

[High cell density culture of phosphotransacetylase mutants of Escherichia coli BL21(DE3)]

Cell culture, organic acid production and foreign protein (TNF) expression of E. coli BL21(DE3) and its pta mutant were investigated. Under shaking conditions, TNF expression in pta mutant increased by 23%. During the fed-batch culture without limitation of specific growth rates, the mutant reached a cell density as high as 32.5 g(DCW)/L and total TNF expression at 2.8 g/L, while the parental strain only obtained 19.5 g(DCW)/L and 0.84 g/L. The results indicate that utility of pta mutant as a host is advantageous in foreign protein expression and high cell density culture. Meanwhile, the analysis data of organic acids accumulated during fed-batch culture showed that as the decrease of acetate production(42% of the parental strain), the accumulation of other organic acids(mainly pyruvate, lactate and succinate) obviously increased. As a result, the amount of total organic acids increased by 123% over its parent. The lactate production may be the main obstacle in further growth of the cells.