Analyzing genetic diversity in luffa and developing a Fusarium wilt-susceptible linked SNP marker through a single plant genome-wide association (sp-GWAS) study.

BACKGROUND: Luffa (Luffa spp.) is an economically important crop of the Cucurbitaceae family, commonly known as sponge gourd or vegetable gourd. It is an annual cross-pollinated crop primarily found in the subtropical and tropical regions of Asia, Australia, Africa, and the Americas. Luffa serves not only as a vegetable but also exhibits medicinal properties, including anti-inflammatory, antidiabetic, and anticancer effects. Moreover, the fiber derived from luffa finds extensive applications in various fields such as biotechnology and construction. However, luffa Fusarium wilt poses a severe threat to its production, and existing control methods have proven ineffective in terms of cost-effectiveness and environmental considerations. Therefore, there is an urgent need to develop luffa varieties resistant to Fusarium wilt. Single-plant GWAS (sp-GWAS) has been demonstrated as a promising tool for the rapid and efficient identification of quantitative trait loci (QTLs) associated with target traits, as well as closely linked molecular markers. RESULTS: In this study, a collection of 97 individuals from 73 luffa accessions including two major luffa species underwent single-plant GWAS to investigate luffa Fusarium wilt resistance. Utilizing the double digest restriction site associated DNA (ddRAD) method, a total of 8,919 high-quality single nucleotide polymorphisms (SNPs) were identified. The analysis revealed the potential for Fusarium wilt resistance in accessions from both luffa species. There are 6 QTLs identified from 3 traits, including the area under the disease progress curve (AUDPC), a putative disease-resistant QTL, was identified on the second chromosome of luffa. Within the region of linkage disequilibrium, a candidate gene homologous to LOC111009722, which encodes peroxidase 40 and is associated with disease resistance in Cucumis melo, was identified. Furthermore, to validate the applicability of the marker associated with resistance from sp-GWAS, an additional set of 21 individual luffa plants were tested, exhibiting 93.75% accuracy in detecting susceptible of luffa species L. aegyptiaca Mill. CONCLUSION: In summary, these findings give a hint of genome position that may contribute to luffa wild resistance to Fusarium and can be utilized in the future luffa wilt resistant breeding programs aimed at developing wilt-resistant varieties by using the susceptible-linked SNP marker.

Histopathology and quantification of green fluorescent protein-tagged Fusarium oxysporum f. sp. luffae isolate in resistant and susceptible Luffa germplasm.

Fusarium oxysporum f. sp. luffae (Folu) is a severe plant pathogen that causes vascular wilt and root rot in Luffa plants worldwide. A green fluorescent protein (GFP)-tagged isolate of Folu (Fomh16-GFP) was utilized to investigate the infection progress and colonization of Fomh16-GFP in resistant (LA140) and susceptible (LA100) Luffa genotypes. Seven days post-inoculation (dpi), it was observed that Fomh16-GFP had successfully invaded and colonized the vascular bundle of all LA100 parts, including the roots, hypocotyl, and stem. Pathogen colonization continued to increase over time, leading to the complete wilting of plants by 14-17 dpi. In LA140, the Fomh16-GFP isolate colonized the roots and hypocotyl vascular system at 7 dpi. Nevertheless, this colonization was restricted in the hypocotyl and decreased significantly, and no fungal growth was detected in the vascular system at 21 dpi. Thus, the resistant genotype might trigger a robust defense mechanism. In addition, while the pathogen was present in LA140, the inoculated plants did not exhibit any symptoms until 28 dpi. Quantitative PCR was utilized to measure the Fomh16-GFP biomass in various parts of LA100 and LA140 at different time points. The findings indicated a positive correlation between the quantity of Fomh16-GFP DNA and disease development in LA100. Alternatively, a high amount of Fomh16-GFP DNA was identified in the roots of LA140. Nonetheless, no significant correlations were found between DNA amount and disease progression in LA140. Aqueous extracts from LA140 significantly reduced Fomh16-GFP spore germination, while no significant reduction was detected using LA100 extracts.IMPORTANCEFusarium wilt of Luffa, caused by Fusarium oxysporum f. sp. luffae (Folu), causes great losses in Luffa plants worldwide. This study used a green fluorescent protein (GFP)-tagged isolate of Folu (Fomh16-GFP) to investigate the infection progress and colonization dynamics of Fomh16-GFP in the resistant and susceptible Luffa genotypes, which could be important in understanding the resistance mechanism of Folu in Luffa plants. In addition, our work highlights the correlations between DNA amount and disease progression in resistant plants using real-time PCR. We observed a positive correlation between the quantity of Fomh16-GFP DNA and disease progression in LA100, while no significant correlation was found in LA140. These results could be valuable to further investigate the resistance mechanism of Luffa genotypes against Folu. Gaining a better understanding of the interaction between Folu and Luffa plants is crucial for effectively managing Fusarium wilt and enhancing resistance in Luffa rootstock and its varieties.

PeCIN8 expression correlates with flower size and resistance to yellow leaf disease in Phalaenopsis orchids.

BACKGROUND: The orchid industry has seen a recent surge in export values due to the floral morphology and versatile applications of orchids in various markets for medicinal, food additive, and cosmetic usages. However, plant-related diseases, including the yellow leaf disease caused by Fusarium solani, have caused significant losses in the production value of Phalaenopsis (up to 30%). RESULTS: In this study, 203 Phalaenopsis cultivars were collected from 10 local orchid nurseries, and their disease severity index and correlation with flower size were evaluated. Larger flowers had weaker resistance to yellow leaf disease, and smaller flowers had stronger resistance. For the genetic relationship of disease resistance to flower size, the genetic background of all cultivars was assessed using OrchidWiz Orchid Database Software and principal component analysis. In addition, we identified the orthologous genes of BraTCP4, namely PeIN6, PeCIN7, and PeCIN8, which are involved in resistance to pathogens, and analyzed their gene expression. The expression of PeCIN8 was significantly higher in the most resistant cultivars (A7403, A11294, and A2945) relative to the most susceptible cultivars (A10670, A6390, and A10746). CONCLUSIONS: We identified a correlation between flower size and resistance to yellow leaf disease in Phalaenopsis orchids. The expression of PeCIN8 may regulate the two traits in the disease-resistant cultivars. These findings can be applied to Phalaenopsis breeding programs to develop resistant cultivars against yellow leaf disease.

High-density genetic map and genome-wide association studies of aesthetic traits in Phalaenopsis orchids.

Phalaenopsis spp. represent the most popular orchids worldwide. Both P. equestris and P. aphrodite are the two important breeding parents with the whole genome sequence available. However, marker-trait association is rarely used for floral traits in Phalaenopsis breeding. Here, we analyzed markers associated with aesthetic traits of Phalaenopsis orchids by using genome-wide association study (GWAS) with the F1 population P. Intermedia of 117 progenies derived from the cross between P. aphrodite and P. equestris. A total of 113,517 single nucleotide polymorphisms (SNPs) were identified in P. Intermedia by using genotyping-by-sequencing with the combination of two different restriction enzyme pairs, Hinp1 I/Hae III and Apek I/Hae III. The size-related traits from flowers were negatively related to the color-related traits. The 1191 SNPs from Hinp1 I/ Hae III and 23 simple sequence repeats were used to establish a high-density genetic map of 19 homolog groups for P. equestris. In addition, 10 quantitative trait loci were highly associated with four color-related traits on chromosomes 2, 5 and 9. According to the sequence within the linkage disequilibrium regions, 35 candidate genes were identified and related to anthocyanin biosynthesis. In conclusion, we performed marker-assisted gene identification of aesthetic traits with GWAS in Phalaenopsis orchids.

Develop an efficient inoculation technique for Fusarium solani isolate "TJP-2178-10" pathogeny assessment in Phalaenopsis orchids.

BACKGROUND: Phalaenopsis is one of the important ornamental plants worldwide. It plays the most significant role in flower exportation in Taiwan. However, the yellow leaf disease caused by Fusarium spp. has reduced the orchid flower yield 10-50 % yearly. Varieties resistant to yellow leaf disease associated with Fusarium is urgently needed for orchid growers and breeders, and is the ultimate solution for the long-term goal. To achieve this, phenotyping is the first step and the most necessary information for further studies, such as resistance gene identification, quantitative trait loci identification, and genome-wide association study. RESULTS: The inoculation of Fusarium was performed in either abbreviated stem or detached leaf, and the pros and cons were compared. The former is the general method of phenotyping for estimating the tolerance to yellow leaf disease of Phalaenopsis, but it is time-consuming and spacy, and thus not suitable for the assessment of large numbers of samples. In contrast, the latter not only showed a similar trend of disease severity with time reduced to only one fourth of the former one but also less space needed. CONCLUSIONS: This solution allows a better phenotyping approach for the fast detection of yellow leaf disease associated with Fusarium in a large number of Phalaenopsis samples.

[Endogenous Pollution and Release Characteristics of Bottom Sediments of Hengshan Reservoir in Yixing City].

To clarify the endogenous pollution and release characteristics of the bottom sediment of Hengshan Reservoir in Yixing City, a typical section of the reservoir was sampled and analyzed. The research results show that the average concentrations of total nitrogen, total phosphorus, and organic matter in the surface sediments of Hengshan Reservoir are 2778 mg·kg-1, 899 mg·kg-1, and 3.1%, respectively. The endogenous pollution is serious, and the downstream sediments are highly polluted upstream of the reservoir. Phosphorus spectroscopic analysis results show that iron-bound phosphorus (Fe-P) and aluminum-bound phosphorus (Al-P) are the main bound phosphorus forms in the sediment, accounting for 28% and 39% of the total phosphorus, respectively. The average concentration of activated phosphorus in the sediment (combination of weakly adsorbed phosphorus, organic phosphorus, and iron phosphorus) is 255 mg·kg-1, accounting for 38% of the total phosphorus. The average release rates of nitrogen and phosphorus in sediments were 18.0 mg·(m2·d)-1 and 0.60 mg·(m2·d)-1. The correlation analysis results show that the organic matter content of the sediment is significantly correlated with the diffusion flux of phosphate, ammonia nitrogen, and ferrous iron (P<0.05), indicating that the mineralization of organic matter in the sediment may be the main release source of nitrogen and phosphorus in the sediment influencing factors.

Identification of high-copy number long terminal repeat retrotransposons and their expansion in Phalaenopsis orchids.

BACKGROUND: Transposable elements (TEs) are fragments of DNA that can insert into new chromosomal locations. They represent a great proportion of eukaryotic genomes. The identification and characterization of TEs facilitates understanding the transpositional activity of TEs with their effects on the orchid genome structure. RESULTS: We combined the draft whole-genome sequences of Phalaenopsis equestris with BAC end sequences, Roche 454, and Illumina/Solexa, and identified long terminal repeat (LTR) retrotransposons in these genome sequences by using LTRfinder and classified by using Gepard software. Among the 10 families Gypsy-like retrotransposons, three families Gypsy1, Gypsy2, and Gypsy3, contained the most copies among these predicted elements. In addition, six high-copy retrotransposons were identified according to their reads in the sequenced raw data. The 12-kb Orchid-rt1 contains 18,000 copies representing 220 Mbp of the P. equestris genome. Southern blot and slot blot assays showed that these four retrotransposons Gypsy1, Gypsy2, Gypsy3, and Orchid-rt1 contained high copies in the large-genome-size/large-chromosome species P. violacea and P. bellina. Both Orchid-rt1 and Gypsy1 displayed various ratios of copy number for the LTR sequences versus coding sequences among four Phalaenopsis species, including P. violacea and P. bellina and small-genome-size/small-chromosome P. equestris and P. ahprodite subsp. formosana, which suggests that Orchid-rt1 and Gypsy1 have been through various mutations and homologous recombination events. FISH results showed amplification of Orchid-rt1 in the euchromatin regions among the four Phalaenopsis species. The expression levels of Peq018599 encoding copper transporter 1 is highly upregulated with the insertion of Orchid-rt1, while it is down regulated for Peq009948 and Peq014239 encoding for a 26S proteasome non-ATP regulatory subunit 4 homolog and auxin-responsive factor AUX/IAA-related. In addition, insertion of Orchid-rt1 in these three genes are all in their intron regions. CONCLUSION: Orchid-rt1 and Gypsy1-3 have amplified within Phalaenopsis orchids concomitant with the expanded genome sizes, and Orchid-rt1 and Gypsy1 may have gone through various mutations and homologous recombination events. Insertion of Orchid-rt1 is in the introns and affects gene expression levels.

Identification of miRNA-eQTLs in maize mature leaf by GWAS.

BACKGROUND: MiRNAs play essential roles in plant development and response to biotic and abiotic stresses through interaction with their target genes. The expression level of miRNAs shows great variations among different plant accessions, developmental stages, and tissues. Little is known about the content within the plant genome contributing to the variations in plants. This study aims to identify miRNA expression-related quantitative trait loci (miR-QTLs) in the maize genome. RESULTS: The miRNA expression level from next generation sequencing (NGS) small RNA libraries derived from mature leaf samples of the maize panel (200 maize lines) was estimated as phenotypes, and maize Hapmap v3.2.1 was chosen as the genotype for the genome-wide association study (GWAS). A total of four significant miR-eQTLs were identified contributing to miR156k-5p, miR159a-3p, miR390a-5p and miR396e-5p, and all of them are trans-eQTLs. In addition, a strong positive coexpression of miRNA was found among five miRNA families. Investigation of the effects of these miRNAs on the expression levels and target genes provided evidence that miRNAs control the expression of their targets by suppression and enhancement. CONCLUSIONS: These identified significant miR-eQTLs contribute to the diversity of miRNA expression in the maize penal at the developmental stages of mature leaves in maize, and the positive and negative regulation between miRNA and its target genes has also been uncovered.

Increased red blood cell distribution width might predict left ventricular hypertrophy in patients with atrial fibrillation.

The presence of left ventricular hypertrophy has been confirmed to be an independent risk factor for stroke and death in patients with atrial fibrillation. This retrospective study aimed to evaluate the potential risk factors for left ventricular hypertrophy in patients with atrial fibrillation.A series of consecutive patients diagnosed with atrial fibrillation between June 2018 and December 2019 were included. The patients' clinical data were analyzed. The cut-off values, sensitivity and specificity of the independent risk factors were calculated using a receiver operating characteristic curve.Among 87 patients with atrial fibrillation, 39 patients with left ventricular hypertrophy and 48 patients without left ventricular hypertrophy were included. Multivariate logistic regression analysis showed that red blood cell distribution width (odds ratio [OR] 4.89, 95% confidence interval [CI]: 1.69-14.13, P < .05) was an independent risk factor, while the concentration of low-density lipoprotein (OR 0.37, 95% CI: 0.17-0.83, P < .05) and left ventricular ejection fraction (OR 0.88, 95% CI: 0.82-0.95, P < .05) were inversely associated with left ventricular hypertrophy in atrial fibrillation patients. The receiver operating characteristic curve demonstrated that the area under the curve was 0.80 (95% CI: 0.71-0.90, P < .05) with a cut-off value of 13.05, and the red blood cell distribution width predicted left ventricular hypertrophy status among atrial fibrillation patients with a sensitivity of 72.1% and a specificity of 76.9%.Red blood cell distribution width was associated with left ventricular hypertrophy in patients with atrial fibrillation.

Dysregulation of expression correlates with rare-allele burden and fitness loss in maize.

Here we report a multi-tissue gene expression resource that represents the genotypic and phenotypic diversity of modern inbred maize, and includes transcriptomes in an average of 255 lines in seven tissues. We mapped expression quantitative trait loci and characterized the contribution of rare genetic variants to extremes in gene expression. Some of the new mutations that arise in the maize genome can be deleterious; although selection acts to keep deleterious variants rare, their complete removal is impeded by genetic linkage to favourable loci and by finite population size. Modern maize breeders have systematically reduced the effects of this constant mutational pressure through artificial selection and self-fertilization, which have exposed rare recessive variants in elite inbred lines. However, the ongoing effect of these rare alleles on modern inbred maize is unknown. By analysing this gene expression resource and exploiting the extreme diversity and rapid linkage disequilibrium decay of maize, we characterize the effect of rare alleles and evolutionary history on the regulation of expression. Rare alleles are associated with the dysregulation of expression, and we correlate this dysregulation to seed-weight fitness. We find enrichment of ancestral rare variants among expression quantitative trait loci mapped in modern inbred lines, which suggests that historic bottlenecks have shaped regulation. Our results suggest that one path for further genetic improvement in agricultural species lies in purging the rare deleterious variants that have been associated with crop fitness.

Suppressive effect of microRNA319 expression on rice plant height.

KEY MESSAGE: miR319 was identified as a dwarf-inducing gene from Shiokari and its dwarf near isogenic line, and its transgenic rice showed a reduced plant height. This finding reveals the potential application of miR319 in future molecular breeding. It is well known that microRNAs (miRNAs) play important roles in plant physiology, especially in development and stress responses. However, little is known about the role of miRNAs in plant height. In this study, the rice cultivar Shiokari and its dwarf near isogenic line Shiokari-d6 were analysed to identify and characterize plant height-associated miRNAs. This anatomic and morphological investigation revealed that the major cause of the shorter height of Shiokari-d6 is the significantly dis-elongated internodes, particularly the second internode and those underneath it. The results of miRNA microarray profiling and real-time RT-PCR indicated that miR319 is expressed at a significantly higher level in Shiokari-d6 than in Shiokari. Transgenic rice overexpressing miR319 in Oryza sativa L. cv. Tainung 67 generated through Agrobacterium-mediated transformation had a stable dwarf phenotype regardless of whether the plants were from the T1 or T2 generation. We also found that the internodes of miR319-overexpressing rice are shortened, particularly the third internode and those underneath it. Furthermore, we identified three putative miR319 target genes that were previously uncharacterized with expression levels that were negatively correlated with the expression of miR319. In conclusion, miR319 is the first miRNA proposed to be involved in plant height regulation, and its function may influence the elongation of internodes, which leads to decreased plant height.

A case study of the relative effects of power plant nitrogen oxides and sulfur dioxide emission reductions on atmospheric nitrogen deposition.

The contrasting effects of point source nitrogen oxides (NOx) and sulfur dioxide (SO2) air emission reductions on regional atmospheric nitrogen deposition are analyzed for the case study of a coal-fired power plant in the southeastern United States. The effect of potential emission reductions at the plant on nitrogen deposition to Escambia Bay and its watershed on the Florida-Alabama border is simulated using the three-dimensional Eulerian Community Multiscale Air Quality (CMAQ) model. A method to quantify the relative and individual effects of NOx versus SO2 controls on nitrogen deposition using air quality modeling results obtained from the simultaneous application of NOx and SO2 emission controls is presented and discussed using the results from CMAQ simulations conducted with NOx-only and SO2-only emission reductions; the method applies only to cases in which ambient inorganic nitrate is present mostly in the gas phase; that is, in the form of gaseous nitric acid (HNO3). In such instances, the individual effects of NOx and SO2 controls on nitrogen deposition can be approximated by the effects of combined NOx + SO2 controls on the deposition of NOy, (the sum of oxidized nitrogen species) and reduced nitrogen species (NHx), respectively. The benefit of controls at the plant in terms of the decrease in nitrogen deposition to Escambia Bay and watershed is less than 6% of the overall benefit due to regional Clean Air Interstate Rule (CAIR) controls.

[Effects of traffic exhausts on children' s neurobehavioral functions scored by neurobehavioral evaluation methods in Quanzhou, Fujian province].

OBJECTIVE: To explore the effects of traffic exhausts on children's neurobehavioral functions. METHODS: A field study was conducted in Quanzhou, Fujian province where two primary schools were chosen based on the numbers of automobiles passing by,and the data of ambient air pollutants from the monitoring system. School B and School A located at the high traffic exhausts pollution area and the clear area, respectively. Neurobehavioral functions of pupils in grade 2 and 3 were scored. RESULTS: School B had very similar score of Ruiwen Test with School A, while the score of Digit Eras Test was lower than that in School A with marginal significance. The scores of Digit Symbol,Aim Tracing, Sign Register and Cormect Number test were 38.5 +/- 9.96, 84.3 +/- 27.83, 37.4 +/- 11.62 and 17.1 +/- 5.88 in School B,respectively, which were significantly lower than those in School A (41.6 +/- 12.97, 95.5 +/- 35.80, 42.3 +/- 15.58 and 18.7 +/- 5.78) respectively. Scores in Digit Symbol,Aim Tracing,Sign Register and Cormect Number of pupils in School B were 2.9, 11.5, 5.6 and 1.6 lower than those in School A after adjusting on other confounding factors. CONCLUSION: It was suggested that traffic exhausts might cause damage to children's neurobehavioral functions.

Identification and characterization of an interleukin-15 homologue from Tetraodon nigroviridis.

Interleukin-15 (IL-15) plays an important role in adaptive immune systems in vertebrates with similar bioactivities to interleukin-2 (IL-2). Here we report molecular cloning, sequence analysis and distribution of an IL-15 homologue from a pufferfish (Tetraodon nigroviridis). It is located within a 3,088 bp genomic fragment, transcribed into a 1,056 bp mRNA including 158 bp 5'UTR (untranslated region), 519 bp ORF (open reading frame) and 379 bp 3'UTR. T. nigroviridis IL-15 is constitutively detectable in tissues and organs selected. Levels of transcripts were observed after various stimulations. Gene organization is similar to mammals and birds, and a high degree of conservation of chromosome synteny exists between them. Systematic genomics search against Takifugu rubripes genome supports our conclusions. The T. nigroviridis IL-15 precursor with 172aa (amino acids) contains a putative 53aa signal peptide, while the mature peptide has a calculated molecular mass of 13.36 kDa and a theoretical pI of 4.67. The protein sequence shares 13.3-62.1% identity with reported IL-15s. Phylogenetic analysis grouped Tetraodon with other fish on a separated branch, excluded from mammalian and avian IL-15s. In addition, our analysis on another annotated T. nigroviridis IL-15 demonstrated that it may be a paralogue of IL-15. To differentiate it from the known IL-15s, we described it as IL-15x.

[Cytoplasmic expression of VP1 gene of coxsackievirus B3].

OBJECTIVE: To increase the immune effect of gene vaccine, T7 RNA polymerase was used to establish a system of cytoplasmic expression. METHODS: (1) The plasmid pT7 EMCVP1, including T7 promoter sequence, 5'-untranslated sequence of encephalomyocarditis (EMC) virus, VP1 sequence of coxsackievirus B3 (CVB3), was cotransfected with the plasmid pAR 3132, which codes for the T7 RNA polymerase, into HeLa cells and murine peritoneal macrophages. (2) The plasmid pT7 EMCVP1 and pAR 3132 were respectively transformed into the attenuated Salmonella typhimurium SL 7207. The two kinds of transformed bacteria were coinfected into murine peritoneal macrophages. RESULTS: (1) The target antigen VP1 in the cytoplasm was about 2-4-fold higher than that of pcDNA3 VP1 singly transfected. (2) After the murine peritoneal macrophages were coinfected by two kinds of transformed bacteria, the target antigen VP1 could also be detected. CONCLUSION: The pT7 EMCVP1 and pAR 3132 could be expressed in the cytoplasm of HeLa cells and murine peritoneal macrophages and the amount of the antigen VP1 increased remarkably as compared with that of pcDNA3 VP1 singly transfected.

In vitro anti-coxsackievirus B(3) effect of ethyl acetate extract of Tian-hua-fen.

AIM: To investigation the anti-coxsackievirus B(3) (CVB(3m)) effect of the ethyl acetate extract of Tian-hua-fen on HeLa cells infected with CVB(3m). METHODS: HeLa cells were infected with CVB(3m) and the cytopathic effects (CPE) were observed through light microscope and crystal violet staining on 96-well plate and A(600) was detected using spectrophotometer. The protective effect of the extract to HeLa cells and the mechanism of the effect were also evaluated through the change of CPE and value of A(600). RESULTS: The extract had some toxicity to HeLa cells at a higher concentration while had a marked inhibitory effect on cell pathological changes at a lower concentration. Consistent results were got through these two methods. We also investigated the mechanism of its anti-CVB(3m) effect and the results indicated that the extract represented an inhibitory effect through all the processes of CVB(3m) attachment, entry, biosynthesis and assemble in cells. CONCLUSION: The results demonstrate that the ethyl acetate extract of Tian-hua-fen has a significant protective effect on HeLa cells infected with CVB(3m) in a dose-dependent manner and this effect exists through the process of CVB(3m) attachment, entry, biosynthesis and assemble in cells, suggesting that the ethyl acetate extract of Tian-hua-fen can be developed as an anti-virus agent.

[Attenuated Salmonella typhimurium as DNA delivery vehicle for DNA-mediated immunization].

OBJECTIVE: To study whether the live attenuated AroA-auxotrophic mutant of Salmonella (S.) typhimurium (SL7207) could be used as DNA delivery vehicle to induce more efficient immune response by using the eukaryotic expression plasmid pCMV-beta as report gene. METHODS: Murine peritoneal macrophages were infected with SL7207(pCMV-beta) in vitro, then the expression of the beta-gal were detected by X-gal staining or RT-PCR. After mice were orally immunized with SL7207(pCMV-beta), the expression of beta-gal in the lymphoid tissue were tested by RT-PCR, humoral responses were tested by ELISA, splenic lymphocyte proliferation were tested by 3H-TdR incorporation and cytotoxic T lymphocyte reaction were tested by JAM test. RESULTS: The results indicated that the plasmid pCMV-beta could be delivered by SL7207 into the nucleus of the murine macrophages efficiently and expressed well in vitro; after mice received oral immunizations with attenuated S.typhimurium SL7207 harboring plasmid pCMV-beta mice, the expression of beta-gal could be detected in the spleen, mesenteric lymph nodes and Peyers patches of the mice. Furthermore, the experiments demonstrated that specific humoral immune responses and cell-mediated immune responses were successfully induced in these immunized mice. Compared with the naked DNA vaccination, SL7207 (pCMV-beta) oral immunization were more efficient in inducing cellular immune responses. CONCLUSIONS: Attenuated Salmonella typhimurium SL7207 could be used as DNA delivery vehicle for oral immunization, which have the ability to deliver the antigen-encoding DNA specifically to APC directly for inducing the specific immune response being dominant with cellular immune response.