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1.
M. Barták H. Vráblíková-Cempírková J. Štepigová J. Hájek P. Váczi K. Večeřová 《Photosynthetica》2008,46(2):161-169
Lichen thalli were exposed to 4 regimes differing in irradiance and duration of irradiation. Photosynthetic efficiency of
thalli was monitored by chlorophyll fluorescence parameters and xanthophyll cycle analysis. Maximal quantum yield of photosystem
2 (FV/FM) decreased gradually with time in long-term treatment. The effect of additional short-term high irradiance (HI) treatment
applied each 24 h was not significant. Nevertheless, short-term HI applied repeatedly on thalli kept in the dark led to a
significant decrease of FV/FM. Non-photochemical quenching recorded during the long-term treatment corresponded to the content of zeaxanthin (Z). In short-term
treatment, however, proportion of Z (and antheraxanthin) to total amount of xanthophyll cycle pigments recovered to the initial
values every 24 h after each repeated short-term HI event in thalli kept in dark. Thus duration of irradiation rather than
irradiance and frequency of HI events is important for a decrease in primary photosynthetic processes in wet thalli of Lasallia pustulata. Rapidly responding photoprotective mechanisms, such as conversion of xanthophyll cycle pigments, are involved mainly in
short-term irradiation events, even at HI. 相似文献
2.
Ozone depletion is highest during spring and summer in Antarctica, coinciding with the seasonal reproduction of most macroalgae.
Propagules are the life-stage of an alga most susceptible to environmental perturbations therefore, reproductive cells of
three intertidal macroalgal species Adenocystis utricularis (Bory) Skottsberg, Monostroma hariotii Gain, and Porphyra endiviifolium (A and E Gepp) Chamberlain were exposed to photosynthetically active radiation (PAR), PAR + UV-A and PAR + UV-A + UV-B radiation
in the laboratory. During 1, 2, 4, and 8 h of exposure and after 48 h of recovery, photosynthetic efficiency, and DNA damage
were determined. Saturation irradiance of freshly released propagules varied between 33 and 83 μmol photons m−2 s−1 with lowest values in P. endiviifolium and highest values in M. hariotii. Exposure to 22 μmol photons m−2 s−1 PAR significantly reduced photosynthetic efficiency in P. endiviifolium and M. hariotii, but not in A. utricularis. UV radiation (UVR) further decreased the photosynthetic efficiency in all species but all propagules recovered completely
after 48 h. DNA damage was minimal or not existing. Repeated exposure of A. utricularis spores to 4 h of UVR daily did not show any acclimation of photosynthesis to UVR but fully recovered after 20 h. UVR effects
on photosynthesis are shown to be species-specific. Among the tested species, A. utricularis propagules were the most light adapted. Propagules obviously possess good repair and protective mechanisms. Our study indicates
that the applied UV dose has no long-lasting negative effects on the propagules, a precondition for the ecological success
of macroalgal species in the intertidal. 相似文献
3.
Tc1, one of the founding members of the Tc1/mariner transposon superfamily, was identified in the nematode Caenorhabditis elegans more than 25 years ago. Over the years, Tc1 and other endogenous mariner transposons became valuable tools for mutagenesis and targeted gene inactivation in C. elegans. However, transposition is naturally repressed in the C. elegans germline by an RNAi-like mechanism, necessitating the use of mutant strains in which transposition was globally derepressed,
which causes drawbacks such as uncontrolled proliferation of the transposons in the genome and accumulation of background
mutations. The more recent mobilization of the Drosophila mariner transposon Mos1 in the C. elegans germline circumvented the problems inherent to endogenous transposons. Mos1 transposition strictly depends on the expression of the Mos transposase, which can be controlled in the germline using inducible
promoters. First, Mos1 can be used for insertional mutagenesis. The mobilization of Mos1 copies present on an extrachromosomal array results in the generation of a small number of Mos1 genomic insertions that can be rapidly cloned by inverse PCR. Second, Mos1 insertions can be used for genome engineering. Triggering the excision of a genomic Mos1 insertion causes a chromosomal break, which can be repaired by transgene-instructed gene conversion. This process is used
to introduce specific changes in a given gene, such as point mutations, deletions or insertions of a tag, and to create single-copy
transgenes. 相似文献
4.
5.
Background
C. elegans has been established as a powerful genetic system. Use of a chemically defined medium (C. elegans Maintenance Medium (CeMM)) now allows standardization and systematic manipulation of the nutrients that animals receive. Liquid cultivation allows automated culturing and experimentation and should be of use in large-scale growth and screening of animals. 相似文献6.
Lichens, representing mutualistic symbioses between photobionts and mycobionts, often accumulate high concentrations of secondary
compounds synthesized by the fungal partner. Light screening is one function for cortical compounds being deposited as crystals
outside fungal hyphae. These compounds can non-destructively be extracted by 100% acetone from air-dry living thalli. Extraction
of atranorin from Physcia aipolia changed the lichen colour from pale grey to green in the hydrated state, whereas acetone-rinsed and control thalli were all
pale grey when dry. Removal of parietin from Xanthoria parietina changed the colour of desiccated thalli from orange to grey. Colour changes were quantified by reflectance measurements.
By a new chlorophyll fluorescence method, screening was assessed as the decrease in incident irradiance (PAR) necessary to
reach identical effective quantum yields of PSII (ΦPSII) in acetone-rinsed and control thalli. Thereby, we estimated a screening efficiency due to cortical atranorin crystals at
61, 38, and 40% of blue, green and red light, respectively, whereas parietin screened 81, 27 and 1% of these wavelength ranges.
Removal of atranorin caused similar levels of increased photoinhibition for P. aipolia in blue, green and red light, whereas parietin-deficient thalli of X. parietina exhibited increased photoinhibition with decreasing wavelengths. Atranorin possibly prevents water from entering the spaces
between the hyphae in the cortex. The air-filled cavities with white atranorin crystals reflect excess light, whereas the
yellow compound parietin absorbs excess light. Thereby, both atranorin and parietin play significant photoprotective roles
for symbiotic green algae, but with compound-specific screening mechanisms. 相似文献
7.
8.
We measured the responses of pigments and chlorophyll a fluorescence parameters of the Antarctic leafy liverwort Cephaloziella varians to snowmelt during austral spring 2005 at Rothera Point on the western Antarctic Peninsula. Although no changes to the concentrations
of UV-B photoprotective pigments were detected during snowmelt, chlorophyll and carotenoid concentrations and maximum photosystem
(PS)II yield (F
v
/F
m) were respectively 88, 60 and 144% higher in the tissues of the liverwort that had recently emerged from snow than in those
under a 10 cm depth of snow. A laboratory experiment similarly showed that effective PSII yield increased rapidly within the
first 45 min after plants sampled from under snow were removed to an illuminated growth cabinet. The pigmentation and PSII
yields of plants during snowmelt were also compared with those of plants in January, during the middle of the growing season
at Rothera Point. During snowmelt, plants had lower F
v
/F
m values, chlorophyll a/b ratios and concentrations of UV-B photoprotective pigments and carotenoids than during mid-season, suggesting that although
there is some recovery of PSII activity and increases in concentrations of photosynthetic pigments during snowmelt, the metabolism
of C. varians is restricted during this period. 相似文献
9.
Zehua Sun Chen Wen Zhengyi Chen Qi’an Zhang Ling Fang Jiang Li Shaotong Jiang Shuqing Cao 《Acta Physiologiae Plantarum》2011,33(3):1025-1030
10.
Growth response and changes in the spectral properties of methanolic extract of an estuarine cyanobacterium, Lyngbya aestuarii Agardh, to UV-B radiation were studied. Increase in growth accompanied by increase in chlorophyll a, protein and carbohydrate content was observed up to 12 h of UV-B irradiation followed by a decline with further increase
in the duration of UV exposure. Carotenoid content progressively increased with the UV-B dose. The organism synthesized, to
a significant extent, mycosporine amino acid-like substances (MAAs) upon UV-B exposure. The cells in the trichome became coiled
followed by formation of small bundles as a response to UV-B radiation. SDS protein profile of the UV irradiated cells showed
repression of 20 and 22 kDa proteins. However, irradiation with UV-B for 6–24 h led to overproduction of 84, 73, 60, 46, 40,
37 KDa proteins, possibly conferring protection to the organism from UV-B. UV irradiated cells cultured in florescent light
for up to 7 days showed revival from UV damage of the pigments and macromolecular contents, suggesting existence of a repair
mechanism in the organism. 相似文献
11.
Photosynthetic and growth characteristics of Mosla chinensis and M. scabra were compared at three irradiances similar to shaded forest understory, forest edge, and open land. At 25 % full ambient irradiance, M. chinensis and M. scabra had similar photosynthetic characteristics, but saturation irradiance, compensation irradiance, and apparent quantum yield of M. chinensis were higher than those of M. scabra at full ambient irradiance and 70 % full ambient irradiance. At the same irradiance treatment, specific leaf area and leaf area ratio of M. chinensis were lower than those of M. scabra. Photon-saturated photosynthetic rate and water use efficiency of M. chinensis, however, were not significantly higher than those of M. scabra, and the leaf area and total biomass were lower than those of M. scabra. As a sun-acclimated plant, the not enough high photosynthetic capacity and lower biomass accumulation may cause that M. chinensis has weak capability to extend its population and hence be concomitant in the community. 相似文献
12.
Calycanthus chinensis is an endangered plant of the national second-grade protection of China restricted in a small area in Zhejiang Province.
We studied parameters of photosynthesis, chlorophyll (Chl) contents, and Chl fluorescence (minimum fluorescence, F0, maximum fluorescence, Fm, variable fluorescence, Fv, and Fv/Fm) of C. chinensis and Chimonanthus praecox. C. chinensis had lower compensation irradiance but higher saturation irradiance than C. praecox. Hence C. chinensis has more advantage in obtaining and utilizing photon energy and higher Chl content, and is more adaptive to higher temperature
and propitious to thermal dissipation than C. praecox. In addition, C. chinensis produces abundant, well-preserved seed with a higher germination rate and a wider adaptability to temperature than C. praecox. Thus C. chinensis is prone to survival and viability, and gets rid of the endangered plant species of the national second-grade protection
of China. 相似文献
13.
A transgenic strain of the nitrogen-fixing filamentous cyanobacterium Anabaena PCC 7120 protected expressed δ-endotoxin proteins of Bacillus thuringiensis subsp. israelensis from damage inflicted by UV-B, a sunlight component that penetrates Earth's ozone layer. This organism, which serves as a
food source to mosquito larvae and could multiply in their breeding sites, may solve the environment-imposed limitations of
B. thuringiensis subsp. israelensis as a mosquito biological control agent.
Received: 20 November 2001 / Accepted: 31 December 2001 相似文献
14.
Summary A liquid-based assay was used to evaluate the ability of Yersinia pseudotuberculosis to form a bacterial biofilm on the nematode Caenorhabditis elegans. After 3 days of incubation in the liquid assay a biofilm was clearly visible by light microscopy on both the head and vulva region of the worms. At times, the biofilm formation on the vulva appeared to prevent the laying of eggs by the adult hermaphrodite; the eggs would later hatch inside of the worm. One possible explanation for the biofilm formation observed on the vulva may be the increased motion of the cuticle surrounding the vulva when the worm is immersed in a liquid culture. This is the first report of biofilm formation on the vulva of C. elegans. 相似文献
15.
Photosynthetic parameters were measured in two invasive weeds, Mikania micrantha and Chromolaena odorata, grown in soil under full, medium, and low irradiance and full, medium, and low water supply. Both species showed significantly
higher net photosynthetic rate, quantum yield of PS 2 photochemistry and photochemical quenching coefficient under high than
low irradiance. For M. micrantha, low irradiance caused decreased chlorophyll content (Chl), Chl a/b ratio and maximum photochemical efficiency of PS 2 (Fv/Fm), while drought decreased Chl content and Fv/Fm and increased nonphotochemical quenching (NPQ). However, these parameters were much less affected in C. odorata except that Chl content and NPQ slightly increased under drought and high irradiance. High irradiance increased xanthophyll
pools in both species, especially M. micrantha under combination with drought. 相似文献
16.
Monica G. Risley Stephanie P. Kelly Justin Minnerly Kailiang Jia Ken Dawson-Scully 《Invertebrate neuroscience : IN》2018,18(2):8
Increased neuronal excitability causes seizures with debilitating symptoms. Effective and noninvasive treatments are limited for easing symptoms, partially due to the complexity of the disorder and lack of knowledge of specific molecular faults. An unexplored, novel target for seizure therapeutics is the cGMP/protein kinase G (PKG) pathway, which targets downstream K+ channels, a mechanism similar to Retigabine, a recently FDA-approved antiepileptic drug. Our results demonstrate that increased PKG activity decreased seizure duration in C. elegans utilizing a recently developed electroconvulsive seizure assay. While the fly is a well-established seizure model, C. elegans are an ideal yet unexploited model which easily uptakes drugs and can be utilized for high-throughput screens. In this study, we show that treating the worms with either a potassium channel opener, Retigabine or published pharmaceuticals that increase PKG activity, significantly reduces seizure recovery times. Our results suggest that PKG signaling modulates downstream K+ channel conductance to control seizure recovery time in C. elegans. Hence, we provide powerful evidence, suggesting that pharmacological manipulation of the PKG signaling cascade may control seizure duration across phyla. 相似文献
17.
P. Selvakumar S. Rajasekar K. Periasamy N. Raaman 《World journal of microbiology & biotechnology》2008,24(10):2125-2131
Melanins are enigmatic pigments that are produced by a wide variety of microorganisms including several species of bacteria
and fungi. For more than 40 years, fungi have been known to produce pigments called melanins. Melanin pigment production by
mushrooms was not intensively studied. The present study was carried out on isolation and characterization of melanin from
an edible mushroom Pleurotus
cystidiosus var. formosensis. The mushroom produced dark mucous mass of hyaline arthrospores on mycelium. The coremia exclusively produced dikaryotic
arthrospores with the remnant of a clamp connection. Continuous cell extension and division in the coremium stipe supplied
cells for arthroconidiation at the coremium apex, which is surrounded by a liquid droplet (coremioliquid). The black coloured
coremea (conidia) were produced by Antromycopsis macrocarpa (anamorph of P. cystidiosus) when cultured on potato dextrose agar medium. The agar plate was incubated at continuous light illumination for high amount
of pigment (coremea) production. The slimy layer of the coremea was extracted and partially purified by alkaline and acid
treatment. The black pigment was confirmed as melanin based on UV, IR and EPR spectra apart from chemical analysis. This is
the first report on characterization of melanin obtained from Pleurotus
cystidiosus var. formosensis. 相似文献
18.
Summary Three closely affiliated species of Heterospathe Scheff. (H. elegans (Becc.) Becc., H. humilis Becc. and H. versteegiana Becc.) from New Guinea are revised. They are reduced to a single species which is divided into two subspecies, and the new
combination H. elegans subsp. humilis (Becc.) M. S. Trudgen & W. J. Baker is made. The subspecies can be readily distinguished by their growth habit. Epitypes
are designated for the three previously published names, as informative material on the habit is not included in the existing
type specimens. A new, potentially related species is described as H. pullenii M. S. Trudgen & W. J. Baker. 相似文献
19.
Carotenoids represent a group of valuable molecules for the pharmaceutical, chemical, food and feed industries, not only because
they can act as vitamin A precursors, but also for their coloring, antioxidant and possible tumor-inhibiting activity. Animals
cannot synthesize carotenoids, and these pigments must therefore be added to the feeds of farmed species. The synthesis of
different natural commercially important carotenoids (β-carotene, torulene, torularhodin and astaxanthin) by several yeast
species belonging to the genera Rhodotorula and Phaffia has led to consider these microorganisms as a potential pigment sources. In this review, we discuss the biosynthesis, factors
affecting carotenogenesis in Rhodotorula and Phaffia strains, strategies for improving the production properties of the strains and directions for potential utility of carotenoid-synthesizing
yeast as a alternative source of natural carotenoid pigments. 相似文献
20.
The ocean quahog, Arctica islandica is not just the longest living bivalve, it is also the longest lived, non-colonial animal known to science. With the maximum
life span potential ever increasing and currently standing in excess of 400 years the clam has recently gained interest as
a potential model organism for ageing research. This review details what is known about the biology of A.
islandica, it discusses observed age-associated changes and reviews previous ageing research undertaken on the species and other long-lived
bivalves which may be applicable to future ageing research and discusses future directions for ageing research with A. islandica. Historically much of the research on bivalves has been targeted at their utilization as a food source, environmental sentinels
and more recently the use of their shells as archives of environmental change. The result of this has been an abundance of
knowledge on bivalve life strategies, and a limited amount of information on the physiological changes in the cells and tissues
of bivalves during the ageing process. However, research into the mechanisms of senescence of long-lived bivalves from a biogerontological
perspective has advanced only recently. The research undertaken thus far has documented age-related differences in anti-oxidant
defences and accumulation of oxidative products but despite the recent attention into ageing of A. islandica it is still to be ascertained if the species experiences senescence. Future directions for ageing research using A. islandica are discussed. 相似文献