The 5'-UTR intron of the midgut-specific BmAPN4 gene affects the level and location of expression in transgenic silkworms

Genome-wide screening reveals repression by nuclear exosome as a prerequisite for intron-mediated enhancement in Saccharomyces cerevisiae

Introns can enhance gene expression, a phenomenon called intron-mediated enhancement (IME). Previously proposed IME mechanisms do not sufficiently explain the variability in enhancement levels, suggesting that IME mechanism has not been fully understood. A comprehensive screening of genes involved in IME can provide valuable insights. Recently, using a luciferase coding sequence (yCLuc), we showed that IME functions by relieving repression rather than simply enhancing expression. The expression of yCLuc is repressed by the specific nucleotide sequence UCUU, and adding an intron relieves this repression in the yeast Saccharomyces cerevisiae. Herein, genome-wide screenings were conducted using S. cerevisiae knockout strain libraries to identify genes involved in IME. For screening, yCLuc was expressed with and without an intron in knockout strains. Consequently, CDC73, a regulator of RNA polymerase II (RNAPII), was identified as essential for enhancement. Additionally, 23 genes specifically involved in the repression were identified. These 23 genes are related to nuclear exosomes, RNA modification, RNAPII regulation, the nuclear pore complex, ribosomes, and chromatin modification. Among these, genes associated with nuclear exosomes, which degrade various RNAs in the nucleus, showed the largest impact on expression. The RNA sequence UCUU has been reported as a target for RNA degradation by nuclear exosomes. These findings suggested that UCUU-containing coding sequences are primarily repressed via RNA degradation by the nuclear exosome through UCUU recognition, with this repression being relieved by the presence of an intron.

Introns increase gene expression in Caenorhabditis elegans by a mechanism that must be at least partly different than in plants

The wide diversity of organisms in which introns stimulate gene expression suggests that this is an ancient phenomenon. However, the mechanisms through which introns boost expression remain poorly understood, and the degree the which the action of introns is evolutionarily conserved is unknown. Here we compared the effect on expression of introns at different positions and tested ten different introns at the same location in a reporter gene in single-copy transgenic nematodes. The introns boosted expression most when near the start of the gene, as previously observed in several organisms. All ten introns tested at the same position increased mRNA accumulation 10- to 17-fold, in contrast to plants where introns vary widely in their effect on expression and relatively few increase mRNA levels 10-fold or more. These results suggest that some aspects of the mechanisms through which introns boost expression are fundamentally different in nematodes and plants.

Transcriptional regulation of Cry2Ab toxin receptor ABCA2 gene in insects involves GATAe and splicing of a 5' UTR intron

Bacillus thuringiensis (Bt) produces Cry toxins that are used to control insect pests worldwide. However, evolution of insect resistance threatens the sustainable application of these toxins. In some cases, Cry toxin resistance has been linked to mutations affecting toxin receptors expression. Previous work identified HaGATAe transcriptional factor (TF) to be involved in the expression of multiple Cry1 receptor genes. Also, it was reported that 5´untranslated region (UTR) could be involved in regulation of gene expression in eukaryotic cells. The ABCA2 protein functions as Cry2A toxin receptor in multiple lepidopteran species. Here, we investigated regulation of HaABCA2 expression in Helicoverpa armigera and in different insect cell lines. Transient expression of HaABCA2 gene resulted in susceptibility to Cry2Ab in Sf9 cells. Transient expression of HaGATAe transcriptional factor in Sf9 cells enhanced the expression of multiple larval midgut proteins including SfABCA2, increasing the susceptibility to activated Cry2Ab. The silencing of HaGATAe expression in H. armigera larvae by RNAi, resulted in lower expression of HaABCA2 which correlated with reduced susceptibility to Cry2Ab. The GATAe-binding site in the promoter of HaABCA2 gene was identified by systematic truncations, site directed mutagenesis and DNA Pull-down analysis. In addition, 5' RACE analysis revealed that HaABCA2 transcripts in larval midgut cells had at least three different 5' UTRs. Here we also show that the retention of an intron in one of these 5' UTRs significantly inhibited the HaABCA2 expression. A short sequence after the start codon of translation of HaABCA2 was identified to be required for the intron removal. These findings provide new insight for mechanism of Cry2Ab resistance in H. armigera.

The BrAFP1 promoter drives gene-specific expression in leaves and stems of winter rapeseed (Brassica rapa L.) under cold induction

BrAFP1(antifreeze protein in winter turnip rape) effectively limits recrystallization and growth of ice crystals. The BrAFP1 expression level determines whether the freezing-induced damage to winter turnip rape plants is avoided. This study analyzed the activity of the BrAFP1 promoters of several varieties at various cold tolerance levels. We cloned the BrAFP1 promoters from five winter rapeseed cultivars. The multiple sequence alignment revealed the presence of one inDel and eight single-nucleotide mutations (SNMs) in the promoters. One of these SNMs (base mutation from C to T) at the -836 site away from the transcription start site (TSS) enhanced the transcriptional activity of the promoter at low temperature. The promoter activity was specific in cotyledons and hypocotyls during the seedling stage and was referential in stems, leaves, and flowers but not the calyx. This consequently drove the downstream gene to be specifically expressed in leaves and stems, but not in roots at low temperature. The truncated fragment GUS staining assays revealed that the core region of the BrAFP1 promoter was included in the 98 bp fragment from the -933 to -836 site away from the TSS, which was necessary for transcriptional activity. The LTR element of the promoter significantly enhanced expression at low temperatures and suppressed expression at moderate temperatures. Moreover, the BrAFP1 5'-UTR intron bound the scarecrow-like transcription factor and enhanced expression at low temperature.

Specific Expression of Antimicrobial Peptides from the Black Soldier Fly in the Midgut of Silkworms (Bombyx mori) Regulates Silkworm Immunity

Antimicrobial peptides are molecules with strong antimicrobial activity and are of substantial interest for the immunization of insects. As a type of dipteran insect that can turn organic waste into animal feed, the black soldier fly (BSF) can "turn waste into treasure". In this study, we investigated the antimicrobial activity of the antimicrobial peptide genes, HiCG13551 and Hidiptericin-1, of BSF in silkworms, by overexpressing the genes specifically in the midgut. Changes in the mRNA levels of the transgenic silkworms after infection with Staphylococcus aureus were evaluated using transcriptome sequencing. The results showed that Hidiptericin-1 had stronger antimicrobial activity than HiCG13551. KEGG enrichment analysis showed that the differentially expressed genes in the transgenic overexpressed Hidiptericin-1 silkworm lines from the D9L strain were mainly enriched in the starch and sucrose metabolism, pantothenate and CoA biosynthesis, drug metabolism (other enzymes), biotin metabolism, platinum drug resistance, galactose metabolism, and pancreatic secretion pathways. In addition, immune-related genes were up-regulated in this transgenic silkworm strain. Our study may provide new insights for future immune studies on insects.

Biochemical characterization and overexpression of an α-amylase (BmAmy) in silkworm, Bombyx mori

Silkworm (Bombyx mori) is the only fully domesticated insect. As an economically important insect, nutrition utilization is important for its productivity. Hence, the present study investigated the expression pattern of BmAmy, an α-amylase, in B. mori. BmAmy protein purification and biochemical characterization were performed, and effects of BmAmy overexpression were assessed. Real-time quantitative reverse transcription polymerase chain reaction indicated that BmAmy transcription was positively correlated with the silkworm's food intate. Moreover, enzymatic activity assay results showed that BmAmy had significant α-amylase activity of about 1 mg/min/mg protein. Furthermore, treatment with mulberry amylase inhibitors MnAI1 and MnAI2 resulted to 89.92% and 93.67% inhibition in BmAmy activity, respectively, and the interaction between BmAmy and MnAI was also confirmed by protein docking analysis. A silkworm line that specifically overexpressed BmAmy in the midgut was generated through piggyBac-based transgenic technology, and compared to those of non-transgenic silkworms, the whole cocoon and cocoon shell weights of these transgenic silkworms increased by 10.13% and 18.32%, respectively, in the female group, and by 5.83% and 6.00%, respectively, in the male group. These results suggested that BmAmy may be a suitable target for breeding better silkworm varieties in the future.

Identification of Helicoverpa armigera promoters for biotechnological applications

Helicoverpa armigera and Helicoverpa zea are highly polyphagous major agricultural pests with a global distribution. Their control is based on insecticides, however, new, effective, and environmentally friendly control tools are required to be developed and validated. In an effort to facilitate the development of advanced biotechnological tools in these species that will take advantage of new powerful molecular biology techniques like CRISPR/Cas9, we used available transcriptomic data and literature resources, in order to identify RNA polymerase II and III promoters active in RP-HzGUT-AW1(MG), a midgut derived cell line from Helicoverpa zea. Following functional analysis in insect cell lines, four RNA polymerase II promoters from the genes HaLabial, HaTsp-2A, HaPtx-I and HaCaudal were found to exhibit high transcriptional activity in vitro. The HaTsp-2A promoter did not exhibit any activity in the non-midgut derived cell lines Sf-9 and Hi-5 despite high sequence conservation among Lepidoptera, suggesting that it may function in a gut specific manner. Furthermore, considering the utility of RNA polymerase III U6 promoters in methodologies such as RNAi and CRISPR/Cas9, we identified and evaluated four different U6 promoters of H. armigera. In vitro experiments based on luciferase and GFP reporter assays, as well as in vivo experiments targeting an essential gene of Helicoverpa, indicate that these U6 promoters are functional and can be used to experimentally silence or knockout target genes through the expression of shRNAs and sgRNAs respectively. Taking our findings together, we provide a set of promoters useful for the genetic manipulation of Helicoverpa species, that can be used in various applications in the context of agricultural biotechnology.

A case-control study on correlation between the single nucleotide polymorphism of CLEC4E and the susceptibility to tuberculosis among Han people in Western China

BACKGROUND

Tuberculosis (TB) is one of the leading causes of morbidity and mortality in Western China. Preclinical studies have suggested the protective effect of the C-type lectin receptor of family 4 member E (CLEC4E) from TB. Herein, we investigated the association between CLEC4E gene variants and TB susceptibility in a western Chinese Han population.

METHODS

We genotyped four single nucleotide polymorphisms (SNPs) rs10841856, rs10770847, rs10770855 and rs4480590 in the CLEC4E gene using the improved multiplex ligation detection reaction (iMLDR) assay in 900 TB cases and 1534 healthy controls.

RESULTS

After stratifying the whole data by sex, it was found that males exhibited mutant allele G of rs10841856 was more strongly associated with increased TB risk after Bonferroni correction (OR = 1.334, 95% CI: 1.142-1.560; P < 0.001 after adjusting for age; p = 0.001 after Bonferroni correction). The genetic model analysis found that rs10841856 was associated with the increased risk of TB among males under the dominant model (OR = 1.557, 95% CI = 1.228-1.984, P < 0.001 after adjusting for age, P < 0.001 after Bonferroni correction). Bioinformatics analysis suggested that rs10841856 might fall in putative functional regions and might be the expression quantitative trait loci (eQTL) for CLEC4E and long noncoding RNA RP11-561P12.5.

CONCLUSIONS

Our study revealed that rs10841856 in the CLEC4E gene might be related to increased TB risk, especially the dominant genetic model among male Han individuals from Western China.

Advances in the Arms Race Between Silkworm and Baculovirus

Insects are the largest group of animals. Nearly all organisms, including insects, have viral pathogens. An important domesticated economic insect is the silkworm moth Bombyx mori. B. mori nucleopolyhedrovirus (BmNPV) is a typical baculovirus and a primary silkworm pathogen. It causes major economic losses in sericulture. Baculoviruses are used in biological pest control and as a bioreactor. Silkworm and baculovirus comprise a well-established model of insect–virus interactions. Several recent studies have focused on this model and provided novel insights into viral infections and host defense. Here, we focus on baculovirus invasion, silkworm immune response, baculovirus evasion of host immunity, and enhancement of antiviral efficacy. We also discuss major issues remaining and future directions of research on silkworm antiviral immunity. Elucidation of the interaction between silkworm and baculovirus furnishes a theoretical basis for targeted pest control, enhanced pathogen resistance in economically important insects, and bioreactor improvement.

Analysis of CACTA transposase genes unveils the mechanism of intron loss and distinct small RNA silencing pathways underlying divergent evolution of Brassica genomes

In comparison with retrotransposons, DNA transposons make up a smaller proportion of most plant genomes. However, these elements are often proximal to genes to affect gene expression depending on the activity of the transposons, which is largely reflected by the activity of the transposase genes. Here, we show that three AT-rich introns were retained in the TNP2-like transposase genes of the Bot1 (Brassica oleracea transposon 1) CACTA transposable elements in Brassica oleracea, but were lost in the majority of the Bot1 elements in Brassica rapa. A recent burst of transposition of Bot1 was observed in B. oleracea, but not in B. rapa. This burst of transposition is likely related to the activity of the TNP2-like transposase genes as the expression values of the transposase genes were higher in B. oleracea than in B. rapa. In addition, distinct populations of small RNAs (21, 22 and 24 nt) were detected from the Bot1 elements in B. oleracea, but the vast majority of the small RNAs from the Bot1 elements in B. rapa are 24 nt in length. We hypothesize that the different activity of the TNP2-like transposase genes is likely associated with the three introns, and intron loss is likely reverse transcriptase mediated. Furthermore, we propose that the Bot1 family is currently undergoing silencing in B. oleracea, but has already been silenced in B. rapa. Taken together, our data provide new insights into the differentiation of transposons and their role in the asymmetric evolution of these two closely related Brassica species.

Heat shock protein 19.9 (Hsp19.9) from Bombyx mori is involved in host protection against viral infection

Adverse environmental conditions cause serious economic losses in sericulture; Bombyx mori nucleopolyhedrovirus (BmNPV) is the primary biotic stress and high temperature is the major abiotic stress in this industry. B. mori heat shock protein 19.9 (Bmhsp19.9) overexpression was previously demonstrated to protect transgenic silkworm H19.9 against extreme temperature. This study analyzed the role of Bmhsp19.9 in H19.9A and H19.9B silkworm lines and BmE cells infected with BmNPV at regular and high temperatures. qPCR results showed that Bmhsp19.9 expression was upregulated in BmE cells and silkworm after BmNPV challenge. Bmhsp19.9 overexpression significantly inhibited BmNPV proliferation in BmE cells. The viral DNA content was significantly decreased in transgenic H19.9 silkworm compared to the control. These results suggested that Bmhsp19.9 was involved in antiviral immunity against BmNPV. Furthermore, Bmhsp19.9 overexpression protected BmE cells against BmNPV under high temperature shock. This indicates that Bmhsp19.9 is a promising candidate for improving silkworm resistance to biotic and abiotic stresses, thereby reducing sericulture losses.

Characterization and potential application of an α-amylase (BmAmy1) selected during silkworm domestication

Efficient resource utilization plays a central role in the high productivity of domesticated plants and animals. Whether artificial selection acts on digestive enzymes in the domesticated silkworm (Bombyx mori), which is larger than its wild ancestor, Bombyx mandarina (B. mandarina), remains unknown. In this study, we present the characteristics of a novel alpha-amylase, BmAmy1, in B. mori. The activity of recombinant BmAmy1 was maximal at 35 °C and pH 9.0, and could be suppressed by amylase inhibitors from mulberry, the exclusive food source of silkworms. Three different transposable element fragments, which were independently inserted in the 5'-upstream regulatory region, might be responsible for the enhanced expression of BmAmy1 in different domesticated silkworm strains as revealed by dual-luciferase reporter assay. The BmAmy1 overexpression increased the weight of female and male B. mori by 11.9% and 6.8%, respectively, compared with non-transgenic controls. Our results emphasize that, by exploring the genetic mechanisms of human-selected traits, the domestication process could be further accelerated through genetic engineering and targeted breeding.

Fluorescent protein expression in the ectomycorrhizal fungus Laccaria bicolor: a plasmid toolkit for easy use of fluorescent markers in basidiomycetes

For long time, studies on ectomycorrhiza (ECM) have been limited by inefficient expression of fluorescent proteins (FPs) in the fungal partner. To convert this situation, we have evaluated the basic requirements of FP expression in the model ECM homobasidiomycete Laccaria bicolor and established eGFP and mCherry as functional FP markers. Comparison of intron-containing and intronless FP-expression cassettes confirmed that intron-processing is indispensable for efficient FP expression in Laccaria. Nuclear FP localization was obtained via in-frame fusion of FPs between the intron-containing genomic gene sequences of Laccaria histone H2B, while cytosolic FP expression was produced by incorporating the intron-containing 5' fragment of the glyceraldehyde-3-phosphate dehydrogenase encoding gene. In addition, we have characterized the consensus Kozak sequence of strongly expressed genes in Laccaria and demonstrated its boosting effect on transgene mRNA accumulation. Based on these results, an Agrobacterium-mediated transformation compatible plasmid set was designed for easy use of FPs in Laccaria. The four cloning plasmids presented here allow fast and highly flexible construction of C-terminal in-frame fusions between the sequences of interest and the two FPs, expressed either from the endogenous gene promoter, allowing thus evaluation of the native regulation modes of the gene under study, or alternatively, from the constitutive Agaricus bisporus gpdII promoter for enhanced cellular protein localization assays. The molecular tools described here for cell-biological studies in Laccaria can also be exploited in studies of other biotrophic or saprotrophic basidiomycete species susceptible to genetic transformation.

Transcriptome analysis of the immune response of silkworm at the early stage of Bombyx mori bidensovirus infection

Bombyx mori bidensovirus (BmBDV) infects silkworm midgut and causes chronic flacherie disease; however, the interaction between BmBDV and silkworm is unclear. Twenty-four hours after BmBDV infection, the midgut was extracted for RNA-seq to analyze the factors associated with BmBDV-invasion and the early antiviral immune response in silkworms. The total reads from each sample were more than 16100000 and the number of expressed genes exceeded 8200. There were 334 upregulated and 272 downregulated differentially expressed genes (DEGs). Gene ontology analysis of DEGs showed that structural constituents of cuticle, antioxidant, and immune system processes were upregulated. Further analysis revealed BmBDV-mediated induction of BmorCPR23 and BmorCPR44, suggesting possible involvement in viral invasion. Antioxidant genes that protect host cells from virus-induced oxidative stress, were significantly upregulated after BmBDV infection. Several genes related to peroxisomes, apoptosis, and autophagy-which may be involved in antiviral immunity-were induced by BmBDV. These results provide insights into the mechanism of BmBDV infection and host defense.

Potential of transferring transgenic DNA from silkworm to chicken

Safety assessment must be conducted before the commercial release of transgenic silkworms. This study was conducted to assess the potential of transferring transgenic DNA from silkworms to other organisms. One hundred hatched male chickens were evenly assigned into 4 groups (T1-4). Groups T1-3 were fed transgenic silkworms P3+5UI with enhanced green fluorescent protein DNA (EGFP) inserted, A4SOR with superoxide reductase DNA (SOR) inserted, and normal silkworm, respectively. Each chicken was fed one silkworm larva every day for 3 weeks. T4 was the normal feeding control. Twenty chickens were randomly selected from each treatment for sacrifice at 22 days of age. The serum was collected individually for biochemical examination, revealing no difference in the analyzed serum parameters between T4 and T1-3. DNA from the duodenum, jejunum, ileum, liver, kidney, and jejunal digesta was extracted for PCR analysis of EGFP, SOR, silkworm housekeeping gene TIF-4A, and chicken ovalbumin gene. No transgenic DNA or TIF-4A was detected in the digesta and tissues of chickens. The same results were observed in chicken upon increasing the amount and frequency of feeding transgenic silkworms, suggesting that the transgenic DNA from silkworms was degraded in the digestive tract and not transferred into the tissues of chicken. This study revealed that transferr recombinant DNA from transgenic silkworm to another organism is unlikely.

Association between CLEC4E gene polymorphism of mincle and pulmonary tuberculosis infection in a northern Chinese population

BACKGROUND

Pulmonary tuberculosis caused by an intracellular pathogen, Mycobacterium tuberculosis continues to exist as a hazardous disease to human life globally. Genetic polymorphisms regulate resistance and susceptibility to tuberculosis. The C-type lectin receptor of family 4 member E (CLEC4E) confers protection against tuberculosis in laboratory animals but its function in influencing exposure or resistance to pulmonary tuberculosis (PTB) in humans remains obscure.

AIM

We conducted this research to analyze the effects or concomitance of CLEC4E gene variations with susceptibility to pulmonary tuberculosis in a northern Chinese population.

METHOD

In this study, 202 participants with pulmonary tuberculosis and 214 controls without PTB were enrolled. Two single nucleotide polymorphisms (SNPs) for CLEC4E on chromosome 12 were selected with a minor allele frequency of >0.05. All the SNPs were genotyped using high resolution melting analysis-PCR.

RESULTS

We estimated and compared two SNPs, rs10841845 and rs10841847. From our study findings, CLEC4E rs10841845 conferred protection against the development of pulmonary TB with a P value of <0.05 and odds ratio of <1 for all models of genetic inheritance. CLEC4E rs10841847 genotypes in co-dominant, Recessive, Dominant models and alleles had a significant statistical difference between patients and controls associated with resistance against the development of PTB (P<0.05 and OR<1).

CONCLUSION

Our findings suggest that variations at rs10841845 and rs10841847 of CLEC4E genes are associated with increased individual protection against PTB.

Enhanced antiviral immunity against Bombyx mori cytoplasmic polyhedrosis virus via overexpression of peptidoglycan recognition protein S2 in transgenic silkworms

In insect innate immunity, peptidoglycan recognition proteins act as pattern recognition receptors, helping hosts combat invasive microorganisms. Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is the main silkworm pathogen that invades the midgut columnar cell layer. We previously reported that B. mori peptidoglycan recognition protein S2 (BmPGRP-S2) was upregulated in silkworm larvae after BmCPV infection. Here, we constructed a transgenic vector overexpressing BmPGRP-S2 under the control of a midgut-specific promoter. Transgenic silkworm lines (PGRPS2-1 and PGRPS2-2) were generated via embryonic microinjection. BmPGRP-S2 was successfully overexpressed in transgenic silkworms and BmE cells. After oral inoculation with BmCPV, the mortality of PGRPS2-1 and PGRPS2-2 decreased by approximately 36% and 32%, respectively, compared with that of the non-transgenic line, and BmCPV mRNA contents were significantly lower. In the PGRPS2-1 line, imd, relish, and the antimicrobial peptide (AMP) genes attacin2, gloverin2, and moricin showed increased expression after viral infection; however, the Toll pathway was not activated. These results indicate that BmPGRP-S2 overexpression can activate the Imd pathway and induce AMP upregulation, enhancing silkworm antiviral resistance.

BmSUC1 is essential for glycometabolism modulation in the silkworm, Bombyx mori

Sucrose is the most commonly transported sugar in plants and is easily assimilated by insects to fulfill the requirement of physiological metabolism. BmSuc1 is a novel animal β-fructofuranosidase (β-FFase, EC 3.2.1.26)-encoding gene that was firstly cloned and identified in silkworm, Bombyx mori. BmSUC1 was presumed to play an important role in the silkworm-mulberry enzymatic adaptation system by effectively hydrolyzing sucrose absorbed from mulberry leaves. However, this has not been proved with direct evidence thus far. In this study, we investigated sucrose hydrolysis activity in the larval midgut of B. mori by inhibition tests and found that sucrase activity mainly stemmed from β-FFase, not α-glucosidase. Next, we performed shRNA-mediated transgenic RNAi to analyze the growth characteristics of silkworm larvae and variations in glycometabolism in vivo in transgenic silkworms. The results showed that in the RNAi-BmSuc1 transgenic line, larval development was delayed, and their body size was markedly reduced. Finally, the activity of several disaccharidases alone in the midgut and the sugar distribution, total sugar and glycogen in the midgut, hemolymph and fat body were then determined and compared. Our results demonstrated that silencing BmSuc1 significantly reduced glucose and apparently activated maltase and trehalase in the midgut. Together with a clear decrease in both glycogen and trehalose in the fat body, we conclude that BmSUC1 acts as an essential sucrase by directly modulating the degree of sucrose hydrolysis in the silkworm larval midgut, and insufficient sugar storage in the fat body may be responsible for larval malnutrition and abnormal petite phenotypes.

Enhancement of antiviral capacity of transgenic silkworms against cytoplasmic polyhedrosis virus via knockdown of multiple viral genes

Bombyx mori cytoplasmic polyhedrosis virus (BmCPV), a major pathogen of silkworms, causes serious economic losses in sericulture. The BmCPV genome contains 10 discrete dsRNA segments; among these, S1, S2, S3, S4, S6, and S7 encode virus structural proteins, whereas S5, S8, S9, and S10 encode nonstructural proteins. In an attempt to create an anti-BmCPV silkworm strain, we constructed transgenic RNAi vector pb-CNS for knockdown of S5, S8, S9, and S10, and pb-SNS targeting S1, S2, S4, S5, and S8. Transgenic silkworm line CNS and SNS were generated via microinjection of the practical diapause silkworm strain Furong. Following infection via the oral administration of a high dose of BmCPV, the mortality rates of the nontransgenic control, CNS, and SNS were 91%, 37%, and 41%, respectively. qPCR showed that the viral mRNA content in CNS and SNS was significantly lower than that in the nontransgenic line. The economic traits of CNS and SNS were not affected. These results suggest that the knockdown of multiple BmCPV genes significantly enhances the antiviral capacity of the silkworm.

Intron-Mediated Enhancement: A Tool for Heterologous Gene Expression in Plants?

Many plant promoters were characterized and used for transgene expression in plants. Even though these promoters drive high levels of transgene expression in plants, the expression patterns are rarely constitutive but restricted to some tissues and developmental stages. In terms of crop improvement not only the enhancement of expression per se but, in particular, tissue-specific and spatial expression of genes plays an important role. Introns were used to boost expression in transgenic plants in the field of crop improvement for a long time. However, the mechanism behind this so called intron-mediated enhancement (IME) is still largely unknown. This review highlights the complexity of IME on the levels of its regulation and modes of action and gives an overview on IME methodology, examples in fundamental research and models of proposed mechanisms. In addition, the application of IME in heterologous gene expression is discussed.

Impact of ACE2 gene polymorphism on antihypertensive efficacy of ACE inhibitors

Angiotensin-converting enzyme 2 (ACE2), a newly discovered member of renin-angiotensin-aldosterone system, counterbalances the actions of angiotensin-converting enzyme. The objective of our study was to assess the association between rs2106809 polymorphism in ACE2 gene and the blood pressure response to ACE inhibitors in untreated hypertensive patients. After a 2-week, double-blind placebo run-in period, either benazepril or imidapril was administered for 6 weeks to 497 patients with mild to moderate essential hypertension. The achieved changes in BP were analyzed for their association with genotypes at ACE2 gene loci. In female hypertensive patients, the genotype frequency of ACE2 rs2106809 was 36.7%, 45.2% and 18.1% for CC, CT and TT genotypes, respectively. After 6 weeks of treatment, the reductions in diastolic blood pressure were significantly greater in female patients carrying the CC or CT genotype compared with those carrying the TT genotype (9.62±6.83 or 10.2±7.2 versus 6.81±6.31 mm Hg, respectively; P=0.045, analysis of variance (ANOVA)). Moreover, the reductions in mean arterial pressure were significantly greater in female patients carrying the CC or CT genotype compared with those carrying the TT genotype (12.1±7.5 or 12.0±7.9 versus 8.38±6.83 mm Hg, respectively; P=0.035, ANOVA). In male hypertensive patients, the genotype frequency of ACE2 rs2106809 was 58.1% and 41.9% for C and T genotypes, respectively. However, no association could be observed in males. We conclude that ACE2 rs2106809 is an important predictive factor of the response to antihypertensive treatment with ACE inhibitors in Chinese female hypertensive patients.

The 5'UTR Intron of Arabidopsis GGT1 Aminotransferase Enhances Promoter Activity by Recruiting RNA Polymerase II

Photorespiration is essential for the detoxification of glycolate and recycling of carbon to the Calvin Benson Bassham cycle. Enzymes participating in the pathway have been identified, and investigations now focus on the regulation of photorespiration by transporters and metabolites. However, regulation of photorespiration on the gene level has not been intensively studied. Here, we show that maximum transcript abundance of Glu:glyoxylate aminotransferase 1 (GGT1) is regulated by intron-mediated enhancement (IME) of the 5' leader intron rather than by regulatory elements in the 5' upstream region. The intron is rich in CT-stretches and contains the motif TGTGATTTG that is highly similar to the IME-related motif TTNGATYTG. The GGT1 intron also confers leaf-specific expression of foreign promoters. Quantitative PCR analysis and GUS activity measurements revealed that IME of the GGT1 5'UTR intron is controlled on the transcriptional level. IME by the GGT1 5'UTR intron was at least 2-fold. Chromatin immunoprecipitation experiments showed that the abundance of RNA polymerase II binding to the intron-less construct is reduced.