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PubMed2025

Fungal and algal lichen symbionts show different transcriptional expression patterns in two climate zones.

In the lichen symbiosis, the fungal and algal partners constitute a closely integrated system. The combination of fungal and algal partners changes along climate gradients in many species, and is expected to be adaptive. However, the functional mechanisms behind this symbiosis-mediated environmental adaptation are unknown. We investigated which transcriptional profiles are associated with specific fungal-algal symbiont pairings found in lichens from high-elevation (Lower Supratemperate) and low-elevation (Lower Mesomediterranean) sites at two extremes of a climatic gradient on Mount Limbara, Sardinia. Using laboratory-acclimatized thalli, we found that lichen fungal and algal symbionts show variable expression profiles between high- and low-elevation individuals: circadian- and temperature-associated genes for fungi and light-responsive genes for algae show climate-specific patterns. High- and low-elevation individuals differentially express sugar transporters in both symbionts, pointing to symmetrical and climate-dependent sugar transport mechanisms between them. A light pulse treatment identified asymmetries between fungal and algal light responses, with high- and low-elevation fungal symbionts but only low-elevation algal symbionts showing a response. Together, these results tie previously observed genomic variation along climatic gradients in a lichen species to functional differences in transcription for the fungal and algal symbionts, contributing to our understanding of environmental specialization and niche-specific partner combinations in lichens.

Lichens↗
PubMed1992

Auxins induce tryptophan decarboxylase activity in radicles of catharanthus seedlings.

Germinating seedlings of Catharanthus roseus produce monoterpenoid indole alkaloids as a result of a transient increase of tryptophan decarboxylase (TDC) activity. The influence of auxins on this transient rise of TDC activity was studied. External application of indolebutyric acid or 2,4-dichlorophenoxyacetic acid at a concentration of 20 to 40 mum enhanced and prolonged the rise in TDC activity in developing seedlings. Auxin treatment also influenced the morphology of the seedlings; it induced a shortening and thickening of the hypocotyl and the radicle and promoted the initiation of lateral roots in the radicle. During development, the radicles of auxin-treated seedlings displayed a gradual increase in TDC activity that was absent in the radicles of untreated controls. Examination of immunoblots revealed anti-TDC reactive proteins in extracts from radicles of auxin-treated seedlings, but none in extracts from radicles of control seedlings. In contrast, TDC activity and immunoreactive protein levels in the aerial parts of controls and auxin-treated seedlings were comparable. Our results indicate that externally applied auxins induce both abnormal development and TDC activity in the radicles of Catharanthus seedlings. Although auxins slightly delayed the light-mediated induction of the cotyledon-specific last step in vindoline biosynthesis (i.e. acetylcoenzyme A: deacetylvindolin-O-acetyltransferase activity), seedlings still synthesized vindoline, one of the major alkaloid end products.

Journal Article↗
PubMed1992

Phytochrome is involved in the light-regulation of vindoline biosynthesis in catharanthus.

The enzyme acetylcoenzyme A:deacetylvindoline 4-O-acetyl-transferase (DAT) catalyzes the final step in the biosynthesis of the monoterpenoid indole alkaloid, vindoline. Previous studies have shown that the appearance of DAT activity in etiolated seedlings of Catharanthus roseus is induced by exposure of seedlings to light and that enzyme activity is restricted principally to the cotyledons. Evidence is now presented that phytochrome is involved in the light-mediated induction of DAT activity in Catharanthus cotyledons.

Journal Article↗
PubMed1970

The regulation of synthesis and storage of chymotrypsin inhibitor I in leaves of potato and tomato plants.

The synthesis and accumulation of chymotrypsin inhibitor I in tomato leaflets is induced by detachment, or by destruction of petiole phloem by steam when followed by incubation of the leaflets in light. The induction process with detached tomato leaflets is similar to that found with detached potato leaflets. The large amount of inhibitor I synthesized per leaflet cell per unit time suggests either that the structural gene is redundant or that an unusually stable messenger RNA is present. In both tomato and potato leaflets the accumulation of inhibitor I is potently inhibited by actinomycin D, puromycin, and cycloheximide, but not by chloramphenicol. Indoleacetic acid is moderately inhibitory, as is 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Glutamine and asparagine are both markedly stimulating. The cumulative data suggest that inhibitor I is a major depot or interim storage protein and that its existence in any particular tissue is under complex controls by both the internal and external environments of the plants.

Chymotrypsin↗
PubMed1999

Overexpression of Pto activates defense responses and confers broad resistance.

The tomato disease resistance (R) gene Pto specifies race-specific resistance to the bacterial pathogen Pseudomonas syringae pv tomato carrying the avrPto gene. Pto encodes a serine/threonine protein kinase that is postulated to be activated by a physical interaction with the AvrPto protein. Here, we report that overexpression of Pto in tomato activates defense responses in the absence of the Pto-AvrPto interaction. Leaves of three transgenic tomato lines carrying the cauliflower mosaic virus 35S::Pto transgene exhibited microscopic cell death, salicylic acid accumulation, and increased expression of pathogenesis-related genes. Cell death in these plants was limited to palisade mesophyll cells and required light for induction. Mesophyll cells of 35S::Pto plants showed the accumulation of autofluorescent compounds, callose deposition, and lignification. When inoculated with P. s. tomato without avrPto, all three 35S::Pto lines displayed significant resistance and supported less bacterial growth than did nontransgenic lines. Similarly, the 35S::Pto lines also were more resistant to Xanthomonas campestris pv vesicatoria and Cladosporium fulvum. These results demonstrate that defense responses and general resistance can be activated by the overexpression of an R gene.

Cell Death↗
PubMed1997

Vitamin C abrogates the deleterious effects of UVB radiation on cutaneous immunity by a mechanism that does not depend on TNF-alpha.

Acute low-dose treatment of murine skin with ultra violet B (UVB) light impairs induction of contact hypersensitivity (CH) to dinitrofluorobenzene (DNFB) in certain inbred strains of mice (termed UVB-susceptible), but not in others (termed UVB-resistant), and promotes tolerance. These deleterious effects of ultraviolet radiation (UVR) are mediated in part by TNF-alpha, which is released from UVR-exposed epidermal and dermal cells. Because UVR damage to skin has also been ascribed in part to the generation of reactive oxygen intermediates (ROIs) such as superoxide anion (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH-), and singlet oxygen ((1)O2), we investigated whether vitamin C (ascorbic acid), which can nullify ROIs, prevents the deleterious effects of UVR on the cutaneous immune system. We found that epicutaneous application of vitamin C (10% L-ascorbic acid solution) abrogated the deleterious effects of acute low-dose UVR on induction of CH and prevented the induction of tolerance. Vitamin C, however, did not reverse the effects of TNF-alpha on CH induction and tolerance. These results indicate that (i) ROIs generated intracutaneously by UVR contribute to the impaired ability of exposed skin to support the induction of CH and to promote the induction of tolerance and (ii) these effects are not dependent on TNF-alpha.

Animals↗
PubMed1975

The induction of melanogenesis by ultraviolet light in the pigmentary system of Rhesus monkeys.

Except for the face, eyelids, friction surfaces, and lips, the epidermis of the rhesus monkey contains no discernible melanocytes. After ultraviolet irradiation, however, dopa-positive dendritic cells appeared. With daily sequential irradiation, the number of histochemically demonstrable dopa-positive dendritic cells peaked after 30 exposures, then declined to a basal level which was maintained for the duration of the experiment (216 exposures or 43 weeks). Pigment cells can be restimulated by shading part of the irradiated area and then reirradiating after 3 months. While shaded, dopa-positive cells disappeared; but when reirradiated, they reappeared, increased, then declined again to a basal level. These melanocytes, unlike those in other primates, require high threshold levels of irradiation to produce a response, have a definite period during which they are active, and transfer very little melanin to the surrounding keratinocytes. Long-term ultraviolet irradiation has no discernible effect on dermal pigment-containing cells.

Animals↗
PubMed1976

Regulation of phenylalanine ammonia-lyase activity in cell-suspension cultures of Petroselinum hortense. Apparent rates of enzyme synthesis and degradation.

The time courses for induced changes in the phenylalanine ammonia-lyase activity at five different stages during the growth cycle of cell-suspension cultures from parsley (Petroselinum hortense Hoffm.) were investigated. Large increases in the enzyme activity, induced either by irradiation or by dilution of a cell culture into fresh medium, were followed by an expotential decline to the initial low level. The maximum inducible level of specific enzyme activity varied within a range of about six-fold, depending on the mode of induction and the growth stage of the cell culture.

Ammonia-Lyases↗
PubMed2000

Response of a Pseudomonas aeruginosa biofilm community to DNA-damaging chemical agents.

Pseudomonas aeruginosa strain RM4440 carries a plasmid-borne fusion of the P. aeruginosa recA gene promoter to a promoterless lux operon from Vibrio fisheri. We tested the response of RM4440 in a biofilm to exposure to a 1-h pulse of each of 17 chemicals known to be toxic to bacteria and other organisms. The induction of light produced from the recA-lux fusion present in RM4440 proved to be sensitive and specific for DNA-damaging chemicals when included in a biofilm environment. This study demonstrates the potential usefulness of this construct for in situ investigation of bacterial communities.

Journal Article↗
PubMed1970

Cellular control of the synthesis and activity of the bacterial luminescent system.

In bioluminescent bacteria growing in shake flasks, the enzyme luciferase has been shown to be synthesized in a relatively short burst during the period of exponential growth. The luciferase gene appears to be completely inactive in a freshly inoculated culture; the pulse of preferential luciferase synthesis which occurs later is the consequence of its activation at the level of deoxyribonucleic acid transcription which is attributed to an effect of a "conditioning" of the medium by the growing of cells. Although cells grown in a minimal medium also exhibit a similar burst of synthesis of the luminescent system, the amount of synthesis is quantitatively less, relative to cell mass. Under such conditions, added arginine results in a striking stimulation of bioluminescence. This is attributed to a stimulation of existing patterns of synthesis and not to induction or derepression per se.

Aldehydes↗
PubMed1985

Pathogenesis of herpes simplex labialis: experimental induction of lesions with UV light.

To develop a model system of herpes simplex labialis which would enable the study of patients before lesion onset, five patients were exposed to various doses of UV light from a sunlamp at their usual site of lesions. Six of 10 treatments resulted in the development of herpes labialis. Three of four treatments with the highest exposure levels led to large, vesicular, virus culture-positive sores. Side effects from sunlamp exposure were minimal.

Herpes Labialis↗
PubMed2006

Molecular characterization and differential expression of cytokinin-responsive type-A response regulators in rice (Oryza sativa).

BACKGROUND: The response regulators represent the elements of bacterial two-component system and have been characterized from dicot plants like Arabidopsis but little information is available on the monocots, including the cereal crops. The aim of this study was to characterize type-A response regulator genes from rice, and to investigate their expression in various organs as well as in response to different hormones, including cytokinin, and environmental stimuli. RESULTS: By analysis of the whole genome sequence of rice, we have identified ten genes encoding type-A response regulators based upon their high sequence identity within the receiver domain. The exon-intron organization, intron-phasing as well as chromosomal location of all the RT-PCR amplified rice (Oryza sativa) response regulator (OsRR) genes have been analyzed. The transcripts of OsRR genes could be detected by real-time PCR in all organs of the light- and dark-grown rice seedlings/plants, although there were quantitative differences. The steady-state transcript levels of most of the OsRR genes increased rapidly (within 15 min) on exogenous cytokinin application even in the presence of cycloheximide. Moreover, the expression of the OsRR6 gene was enhanced in rice seedlings exposed to salinity, dehydration and low temperature stress. CONCLUSION: Ten type-A response regulator genes identified in rice, the model monocot plant, show overlapping/differential expression patterns in various organs and in response to light. The induction of OsRR genes by cytokinin even in the absence of de novo protein synthesis qualifies them to be primary cytokinin response genes. The induction of OsRR6 in response to different environmental stimuli indicates its role in cross-talk between abiotic stress and cytokinin signaling. These results provide a foundation for further investigations on specific as well as overlapping cellular functions of type-A response regulators in rice.

Amino Acid Sequence↗
PubMed1978

The Schistosoma japonicum egg granuloma. II. Cellular composition, granuloma size, and immunologic concomitants.

Studies of granulomatous hypersensitivity to Schistosoma japonicum eggs were performed at various time periods up to 20 wk after the induction of light infections in mice. Cell populations which were determined in granulomas isolated from the livers revealed a maximum in the total number of cells at 6 wk with a decline of 36% by 20 wk. Large mononuclear cells were predominant at all time periods, with eosinophils being the second most common cell. Measurements of granuloma diameters around single viable eggs in the livers also revealed peak size at 6 wk with a decline of 51% between 16 and 24 wk. Immunodiffusion analysis demonstrated the presence of precipitating antibodies as early as 7 wk after infection. Investigations of lymphocyte blastogenesis revealed a profound depression in response to T-cell mitogens by 8 wk of infection. Studies of footpad swelling to soluble S. japonicum egg antigens revealed massive immediate reactions starting at 6 wk. but no delayed reactivity over a period from 3 to 20 wk. All of these results are related to differences in the biology of S. japonicum in comparison with S. mansoni with respect to the earlier onset of egg production, the much larger numbers of eggs produced, and the possibility of differences in the antigens emitted by the eggs.

Animals↗