T-DNA genes responsible for inducing a necrotic response on grape vines

Agrobacterium tumefaciens supervirulent strain A281 induces a progressive necrotic response, rather than tumor formation, when inoculated on stems of several grape cultivars. The Ti plasmid, and specifically its T-DNA, is required for the process. In the present study, 40 T-DNA insertion mutants of A281 were generated via transposon mutagenesis and tested for their necrosis-inducing ability on grape stems in vitro. Ten mutants were attenuated in inducing necrogenesis. Restriction mapping and DNA sequencing revealed that at least two genes, tms1 and 6b, whose gene products are involved in the synthesis and activity modulation of auxin, are responsible for inducing necrogenesis. Double mutants of tms1 and 6b were totally non-necrogenic. The orientation of grapevine stem explants showed strong effects on the occurrence and progress of necrogenesis. Inoculation of Agrobacterium on physiological basal ends resulted in the greatest degree of necrogenesis. In addition, gene 5 of T-DNA, which modulates auxin responses in plants by the autoregulated synthesis of an auxin antagonist, was found to be separated from other TL-DNA genes by a novel insertion sequence, IS1312. Since a T-DNA borderlike sequence occurs in IS1312, gene 5 might not always be transferred into plants. Based on the accumulated data, we propose that the necrogenesis induced by Agrobacterium results from the sensitivity of grapevine cells to elevated levels of auxin or a precursor of auxin.

Sequence and distribution of IS1312: evidence for horizontal DNA transfer from Rhizobium meliloti to Agrobacterium tumefaciens

Two novel insertion sequences, IS1312 and IS1313, were found in pTiBo542, the Ti plasmid of Agrobacterium tumefaciens strains Bo542 and A281. Nucleotide sequencing and Southern hybridization revealed that IS1312 and IS1313 are homologous to Rhizobium meliloti ISRm1 and ISRm2, respectively. IS1312, ISRm1, and another Agrobacterium insertion sequence, IS426, belong to the same IS3 family of insertion sequences; however, IS1312 is more closely related to the Rhizobium ISRm1 than it is to the Agrobacterium IS426. The distribution patterns of these insertion elements and their sequence similarities suggest that IS1312 and IS1313 were horizontally transferred from R. meliloti to A. tumefaciens.

Mechanisms of IL-4-mediated suppression of IP-10 gene expression in murine macrophages

The mechanisms involved in negative regulation of IFN-gamma-induced IP-10 mRNA expression by IL-4 have been examined in an immortalized murine macrophage cell line (ANA-1). As in primary peritoneal macrophages, IL-4 selectively inhibits the production of IP-10 mRNA by IFN-gamma-treated ANA-1 cells. Expression of another IFN-gamma-inducible gene (D3) was not affected by co-treatment with IL-4. Suppression of IFN-gamma-induced IP-10 mRNA expression by IL-4 is mediated at the level of transcription. IFN-gamma-induced transcription of CAT expression driven by a 243-bp IP-10 promoter fragment was also sensitive to the suppressive effects of IL-4. In contrast, LPS-induced CAT expression was unaffected under identical experimental conditions. The positive transcriptional response to IFN-gamma required an interferon stimulus response element (ISRE) sequence motif located approximately 230 bp upstream from the transcription start site of the IP-10 gene. That this site is the target of the suppressive action of IL-4 is indicated by the ability of IL-4 to inhibit IFN-gamma-mediated transcription from this ISRE sequence in the context of a heterologous promoter. Finally, both IFN-gamma and IL-4 can enhance or induce expression of distinct nuclear factors that exhibit ISRE-specific binding activity. IL-4 does not suppress the IFN-gamma-induced ISRE binding activity. Together, these findings demonstrate that IL-4 inhibits IP-10 mRNA production in murine macrophages by suppressing the formation of new transcripts. Both positive and negative transcriptional activity appears dependent on activation of factors that recognize the ISRE.

Mechanisms of IL-4-mediated suppression of IP-10 gene expression in murine macrophages

The mechanisms involved in negative regulation of IFN-gamma-induced IP-10 mRNA expression by IL-4 have been examined in an immortalized murine macrophage cell line (ANA-1). As in primary peritoneal macrophages, IL-4 selectively inhibits the production of IP-10 mRNA by IFN-gamma-treated ANA-1 cells. Expression of another IFN-gamma-inducible gene (D3) was not affected by co-treatment with IL-4. Suppression of IFN-gamma-induced IP-10 mRNA expression by IL-4 is mediated at the level of transcription. IFN-gamma-induced transcription of CAT expression driven by a 243-bp IP-10 promoter fragment was also sensitive to the suppressive effects of IL-4. In contrast, LPS-induced CAT expression was unaffected under identical experimental conditions. The positive transcriptional response to IFN-gamma required an interferon stimulus response element (ISRE) sequence motif located approximately 230 bp upstream from the transcription start site of the IP-10 gene. That this site is the target of the suppressive action of IL-4 is indicated by the ability of IL-4 to inhibit IFN-gamma-mediated transcription from this ISRE sequence in the context of a heterologous promoter. Finally, both IFN-gamma and IL-4 can enhance or induce expression of distinct nuclear factors that exhibit ISRE-specific binding activity. IL-4 does not suppress the IFN-gamma-induced ISRE binding activity. Together, these findings demonstrate that IL-4 inhibits IP-10 mRNA production in murine macrophages by suppressing the formation of new transcripts. Both positive and negative transcriptional activity appears dependent on activation of factors that recognize the ISRE.

Synergistic cooperation between T cell lymphokines for induction of the nitric oxide synthase gene in murine peritoneal macrophages

The ability of T cell-derived cytokines to induce the expression of the nitric oxide synthase (NOS) gene in murine peritoneal macrophages was examined. IL-2 or TNF-alpha alone had no effect either on gene expression or enzyme activity, whereas IFN-gamma had only modest activity. When IL-2 or TNF-alpha were used in combination with IFN-gamma, there was a marked cooperative induction of both mRNA and enzyme activity. The cooperative effects were truly synergistic, as the consequences of combined cytokine treatment were many times greater than was seen with any of the agents acting independently. The expression of NOS mRNA and enzyme activity in response to combined lymphokine treatments was a continuous process reaching optimal levels between 24 and 48 h after stimulation. Concentration dependency for both IL-2 and TNF-alpha suggested that their effects were mediated through interaction with the corresponding defined cell surface receptors. Human rTNF-alpha was as effective a stimulus as murine TNF-alpha; because human TNF-alpha is recognized only by the p55 Type II TNF receptor, this structure appears to mediate the response to TNF-alpha. When IL-2 and TNF-alpha were added at saturating doses in the presence of IFN-gamma, there was an additive effect on NOS mRNA expression suggesting that IL-2 and TNF-alpha cooperate with IFN-gamma through at least partially distinct intracellular signaling pathways. Expression of NOS mRNA in response to IFN-gamma/IL-2 or IFN-gamma/TNF-alpha treatment required protein synthesis, suggesting that cooperative cytokine induction of NOS involves the intermediate expression of new gene products. Such molecular controls for regulation of inducible macrophage gene expression can be contrasted with regulatory control of other inflammatory genes such as IP-10 and TNF-alpha.

Synergistic cooperation between T cell lymphokines for induction of the nitric oxide synthase gene in murine peritoneal macrophages

The ability of T cell-derived cytokines to induce the expression of the nitric oxide synthase (NOS) gene in murine peritoneal macrophages was examined. IL-2 or TNF-alpha alone had no effect either on gene expression or enzyme activity, whereas IFN-gamma had only modest activity. When IL-2 or TNF-alpha were used in combination with IFN-gamma, there was a marked cooperative induction of both mRNA and enzyme activity. The cooperative effects were truly synergistic, as the consequences of combined cytokine treatment were many times greater than was seen with any of the agents acting independently. The expression of NOS mRNA and enzyme activity in response to combined lymphokine treatments was a continuous process reaching optimal levels between 24 and 48 h after stimulation. Concentration dependency for both IL-2 and TNF-alpha suggested that their effects were mediated through interaction with the corresponding defined cell surface receptors. Human rTNF-alpha was as effective a stimulus as murine TNF-alpha; because human TNF-alpha is recognized only by the p55 Type II TNF receptor, this structure appears to mediate the response to TNF-alpha. When IL-2 and TNF-alpha were added at saturating doses in the presence of IFN-gamma, there was an additive effect on NOS mRNA expression suggesting that IL-2 and TNF-alpha cooperate with IFN-gamma through at least partially distinct intracellular signaling pathways. Expression of NOS mRNA in response to IFN-gamma/IL-2 or IFN-gamma/TNF-alpha treatment required protein synthesis, suggesting that cooperative cytokine induction of NOS involves the intermediate expression of new gene products. Such molecular controls for regulation of inducible macrophage gene expression can be contrasted with regulatory control of other inflammatory genes such as IP-10 and TNF-alpha.

Expression of soybean-embryo lipoxygenase 2 in transgenic tobacco tissue

To assess the role of lipoxygenase (LOX; EC 1.13.11.12) in plants, we increased the expression of LOX in the tissues of Nicotiana tabacum L. cv. 'KY 14' by over-expression of the LOX2 gene from the soybean (Glycine max (L.) Merrill) embryo. The LOX2 cDNA was manipulated by replacing its 5'-untranslated sequence with the translational enhancer of the alfalfa mosaic virus (AMV), and subcloned into a plant expression vector, 3' to a duplicated cauliflower mosaic virus 35S promoter. The AMV-LOX2 construct was transferred into tobacco using Agrobacterium tumefaciens strain A281. The LOX2 was expressed in transgenic tobacco calli, leaves of transgenic plants, and their seed progeny at levels up to 0.1-0.2% of the total extracted protein. The introduced LOX2 affected fatty-acid oxidative metabolism as evidenced by a 50-529% increase in C6-aldehyde production. The impact on C6-aldehyde formation was greater than the effect on production of fatty-acid hydroperoxides. This is consistent with other studies indicating the greater propensity of soybean embryo LOX2 in generating C6-aldehydes than that of other well-characterized LOX isozymes.

Quasi-periodic motion in a hybrid optical bistable system with a short delay

The dynamical behavior of a hybrid optical bistable system with a short delay is calculated numerically in detail. The quasi-periodic motion and frequency locking of the system are observed experimentally.

[The status of human papillomavirus 16 DNA in the tissues of human esophagus carcinoma]

DNAs from 24 cases of human esophagus carcinoma and 24 cases of corresponding para-carcinoma tissues were detected by dot hybridization and Southern hybridization techniques using human papillomavirus (HPV) 16 type DNA as probe. The results indicated that the positive rate of the HPV 16 DNA hybridization was 50% (12/24) in esophagus carcinoma tissues, and 37% (9/24) in para-carcinoma tissues. The results of Southern hybridization showed obviously the positive hybridizing band in the zone of 7.2 kb in smear. It implied that HPV 16 DNA was possibly integrated into the tissue's DNA of esophagus carcinoma. In the fetal esophagus tissues as negative control, 3 cases out of 4 showed positive results. The significance has to be further investigated. This experiment has studied the status of HPV 16 type in the tissues of esophagus carcinoma and para-carcinoma at molecular level. This is just a study of the virus etiology of esophagus carcinoma.