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Li Kang

Publications and source records attributed to Li Kang.

10 recordsLinked to original sources
PubMed2006

Functional characterization of Nicotiana benthamiana homologs of peanut water deficit-induced genes by virus-induced gene silencing.

Determining the functional role of genes that are differentially regulated during a stress response is challenging. In this study, few water deficit-induced genes from peanut were characterized in Nicotiana benthamiana using virus-induced gene silencing (VIGS) and their relevance for stress adaptation was validated. Twenty-five cDNA clones from peanut water deficit stress-induced cDNA library that had more than 50% nucleotide similarity with N. benthamiana or tomato homologs were selected. VIGS in peanut is not yet feasible and therefore we characterized these 25 genes in N. benthamiana. Increased membrane damage was seen under water deficit stress in most of the silenced plants signifying that many of these stress-induced genes are important to confer drought tolerance. Among the genes tested, silencing by homolog of flavonol 3-O-glucosyltransferase (F3OGT), homolog of alcohol dehydrogenase, homologous to salt inducible protein, and homolog of heat shock protein 70 showed more visible wilting symptoms compared with the control plants during water deficit stress. Interestingly, down-regulation of two genes, homologous to aspartic proteinase 2, and homolog of Jumonji class of transcription factor showed relative drought tolerant phenotypes. F3OGT silenced plants showed more wilting symptoms, membrane damage and chlorophyll degradation than any other silenced plants during water deficit. Our results demonstrate that VIGS approach can be used to characterize and assess the functional relevance of water deficit stress-induced cDNAs in a heterologous species.

Anthocyanins↗
PubMed2006

Computational estimation and experimental verification of off-target silencing during posttranscriptional gene silencing in plants.

Successful application of posttranscriptional gene silencing (PTGS) for gene function study in both plants and animals depends on high target specificity and silencing efficiency. By computational analysis with genome and/or transcriptome sequences of 25 plant species, we predicted that about 50% to 70% of gene transcripts in plants have potential off-targets when used for PTGS that could obscure experimental results. We have developed a publicly available Web-based computational tool called siRNA Scan to identify potential off-targets during PTGS. Some of the potential off-targets obtained from this tool were tested by measuring the amount of off-target transcripts using quantitative reverse transcription-PCR. Up to 50% of the predicted off-target genes tested in plants were actually silenced when tested experimentally. Our results suggest that a high risk of off-target gene silencing exists during PTGS in plants. Our siRNA Scan tool is useful to design better constructs for PTGS by minimizing off-target gene silencing in both plants and animals.

Agrobacterium tumefaciens↗
PubMed2006

Chronic ethanol feeding suppresses beta-adrenergic receptor-stimulated lipolysis in adipocytes isolated from epididymal fat.

Chronic ethanol consumption disrupts G protein-dependent signaling pathways in rat adipocytes. Because lipolysis in adipocytes is regulated by G protein-mediated cAMP signal transduction, we hypothesized that cAMP-regulated lipolysis may be vulnerable to long-term ethanol exposure. Male Wistar rats were fed a liquid diet containing ethanol as 35% of total calories or pair-fed a control diet that isocalorically substituted maltose dextrins for ethanol for 4 wk. Lipolysis was measured by glycerol release over 1 h with or without agonists in adipocytes isolated from epididymal fat. Chronic ethanol feeding decreased beta-adrenergic receptor-stimulated lipolysis, but had no effect on basal lipolysis. In response to beta-adrenergic activation, the early peak of cAMP accumulation was suppressed after ethanol feeding, although the basal cAMP concentration in adipocytes did not differ between pair- and ethanol-fed rats. The suppression in cAMP accumulation caused by ethanol feeding was associated with increased activity of phosphodiesterase 4. Chronic ethanol feeding also decreased beta-adrenergic receptor-stimulated protein kinase A activation and phosphorylation of its downstream proteins, perilipin A and hormone-sensitive lipase, the primary lipase-mediating lipolysis. In conclusion, these data suggest that chronic ethanol feeding increased phosphodiesterase 4 activity in adipocytes, resulting in decreased accumulation of cAMP in response to beta-adrenergic activation and a suppression of beta-adrenergic stimulation of lipolysis.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2005

Bifidobacteria DNA induces murine macrophages activation in vitro.

Previous studies have shown that oligodeoxynucleotides containing unmethylated CpG motifs were used as adjuvants for immunoregulation and immune response. This study was to explore the activation effects of Bifidobacteria DNA containing unmethylated CpG motifs (CpG DNA) on murine macrophage J774A.1 cells. The genomic DNA of Bifidobacteria was extracted and purified, and the methylation degree of CpG motifs was tested. The phagocytic ability of the macrophages was detected by flow cytometry. The cytokines (IL-1beta, IL-6, IL-12p40 and TNF-alpha) levels in the culture supernatants of Bifidobacteria DNA treated J774A.1 cells were assayed by ELISA. The content of nitric oxide (NO) was detected by Griess reagent. After treated with Bifidobacteria DNA for 24 h, Nile Red stain increased in J774A.1 macrophage, which suggested that the lipid metabolism increased in the macrophages. The phagocytic ability and levels of NO and cytokines of IL-1beta, IL-6, IL-12p40 and TNF-alpha were significantly higher than PBS group and CT DNA group. The results indicated that Bifidobacteria DNA could activate murine macrophages J774A.1, which could provide scientific basis for the research and application of microorganism DNA preparation.

Animals↗
PubMed2004

Pseudomonas Type III effector AvrPto suppresses the programmed cell death induced by two nonhost pathogens in Nicotiana benthamiana and tomato.

Many gram-negative bacterial pathogens rely on a type III secretion system to deliver a number of effector proteins into the host cell. Though a number of these effectors have been shown to contribute to bacterial pathogenicity, their functions remain elusive. Here we report that AvrPto, an effector known for its ability to interact with Pto and induce Pto-mediated disease resistance, inhibited the hypersensitive response (HR) induced by nonhost pathogen interactions. Pseudomonas syringae pv. tomato T1 causes an HR-like cell death on Nicotiana benthamiana. This rapid cell death was delayed significantly in plants inoculated with P. syringae pv. tomato expressing avrPto. In addition, P. syringae pv. tabaci expressing avrPto suppressed nonhost HR on tomato prf3 and ptoS lines. Transient expression of avrPto in both N. benthamiana and tomato prf3 plants also was able to suppress nonhost HR. Interestingly, AvrPto failed to suppress cell death caused by other elicitors and nonhost pathogens. AvrPto also failed to suppress cell death caused by certain gene-for-gene disease resistance interactions. Experiments with avrPto mutants revealed several residues important for the suppression effects. AvrPto mutants G2A, G99V, P146L, and a 12-amino-acid C-terminal deletion mutant partially lost the suppression ability, whereas S94P and 196T enhanced suppression of cell death in N. benthamiana. These results, together with other discoveries, demonstrated that suppression of host-programmed cell death may serve as one of the strategies bacterial pathoens use for successful invasion.

Agrobacterium tumefaciens↗
PubMed2004

Agrodrench: a novel and effective agroinoculation method for virus-induced gene silencing in roots and diverse Solanaceous species.

Summary Virus-induced gene silencing (VIGS) is an extremely powerful tool for plant functional genomics. We used Tobacco rattle virus (TRV)-derived VIGS vectors expressed from binary vectors within Agrobacterium to induce RNA silencing in plants. Leaf infiltration is the most common method of agroinoculation used for VIGS but this method has limitations as it is laborious for large-scale screening and some plants are difficult to infiltrate. Here we have developed a novel and simple method of agroinoculation, called 'agrodrench', where soil adjacent to the plant root is drenched with an Agrobacterium suspension carrying the TRV-derived VIGS vectors. By agrodrench we successfully silenced the expression of phytoene desaturase (PDS), a 20S proteasome subunit (PB7) or Mg-protoporphyrin chelatase (Chl H) encoding genes in Nicotiana benthamiana and in economically important crops such as tomato, pepper, tobacco, potato, and Petunia, all belonging to the Solanaceae family. An important aspect of agrodrench is that it can be used for VIGS in very young seedlings, something not possible by the leaf infiltration method, which usually requires multiple fully expanded leaves for infiltration. We also demonstrated that VIGS functioned to silence target genes in plant roots. The agrodrench method of agroinoculation was more efficient than the leaf infiltration method for VIGS in roots. Agrodrench will facilitate rapid large-scale functional analysis of cDNA libraries and can also be applied to plants that are not currently amenable to VIGS technology by conventional inoculation methods.

Gene Expression Regulation, Plant↗
PubMed2004

[Study on the genetic damage in mice induced by the volatile organic compounds of decoration materials].

OBJECTIVE: To study genetic damage of mice caused by the volatile organic compounds (VOC) of decoration materials. METHODS: Fifty-five hotel guest rooms newly decorated within 6 months and 18 hotel guest rooms not decorated within 3 years were selected to determine the concentrations of 6 main VOC (benzene, methylbenzene, dimethylbenzene, ethyl acetate, butyl acetate, formaldehyde) in the air. Mice were exposed to VOC with the concentrations of 5, 10, 20, 40 times respectively as high as those present in the newly decorated rooms in an exposure cabinet for 15 days. DNA damage of peripheral lymphocytes of the mice was determined by single cell gel electrophoresis (SCGE) and bone marrow micronucleus test. RESULTS: The concentrations of benzene, methylbenzene, dimethylbenzene, ethyl acetate, butyl acetate and formaldehyde in the rooms newly decorated within 6 months (6.50, 3.00, 6.70, 41.33, 1.70 and 0.14 mg/m(3) respectively) were significantly higher than those in rooms not decorated within 3 years (0.08, 0.94, 1.38, 0.25, 0.25, 0.01 mg/m(3), P < 0.01). DNA damage rates of peripheral lymphocytes in the concentrations of 10, 20, 40 times of exposure groups were significantly higher than those in the control groups (P < 0.05 or P < 0.01), and the frequencies of micronucleus in the mice exposed to 40 times of concentration was significantly higher than that in control group. CONCLUSION: High concentrations of the volatile organic chemical compounds may cause genetic damage in mice. SCGE test is more sensitive than micronucleus test.

Air Pollutants↗
PubMed2003

Interplay of the Arabidopsis nonhost resistance gene NHO1 with bacterial virulence.

It is poorly understood why a particular plant species is resistant to the vast majority of potential pathogens that infect other plant species, a phenomenon referred to as "nonhost" resistance. Here, we show that Arabidopsis NHO1, encoding a glycerol kinase, is required for resistance to and induced by Pseudomonas syringae isolates from bean and tobacco. NHO1 is also required for resistance to the fungal pathogen Botrytis cinerea, indicating that NHO1 is not limited to bacterial resistance. Strikingly, P. s. pv. tomato DC3000, an isolate fully virulent on Arabidopsis, actively suppressed the NHO1 expression. This suppression is abolished in coi1 plants, indicating that DC3000 required an intact jasmonic acid signaling pathway in the plant to suppress NHO1 expression. Constitutive overexpression of NHO1 led to enhanced resistance to this otherwise virulent bacterium. The presence of avrB in DC3000, which activates a cultivar-specific "gene-for-gene" resistance in Arabidopsis, restored the induction of NHO1 expression. Thus, NHO1 is deployed for both general and specific resistance in Arabidopsis and targeted by the bacterium for parasitism.

Amino Acid Sequence↗