72 research outputs found
Using geomorphic and biological indicators of coastal uplift for the evaluation of paleoseismicity and
The westernmost part of the Gulf of Corinth (Greece) is an area of very fast extension (~15 mm/yr
according to geodetic measurements) and active normal faulting, accompanied by intense coastal uplift and
high seismicity. This study presents geomorphic and biological evidence of Holocene coastal uplift at the
western extremity of the Gulf, where such evidence was previously unknown. Narrow shore platforms
(benches) and rare notches occur mainly on Holocene littoral conglomerates of uplifting small fan deltas.
They are perhaps the only primary paleoseismic evidence likely to provide information on earthquake
recurrence at coastal faults in the specific part of the Rift system, whereas dated marine fauna can provide
constraints on average Holocene coastal uplift rate.
The types of geomorphic and biological evidence identified are not ideal, and there are limitations and
pitfalls involved in their evaluation. In a first approach, 5 uplifted paleoshorelines may be indentified, at 0.4-
0.7, 1.0-1.3, 1.4-1.7, 2.0-2.3 and 2.8-3.4 m a.m.s.l. They probably formed after 1728 or 2250 Cal. B.P.
(depending on the marine reservoir correction used in the calibration of measured radiocarbon ages). A
most conservative estimate for the average coastal uplift rate during the Late Holocene is 1.6 or 1.9 mm/yr
minimum (with different amounts of reservoir correction). Part of the obtained radiocarbon ages of
Lithophaga sp. allows for much higher Holocene uplift rates, of the order of 3-4 mm/yr, which cannot be
discarded given that similar figures exist in the bibliography on Holocene and Pleistocene uplift at
neighbouring areas. They should best be cross-checked by further studies though.
That the identified paleoshoreline record corresponds to episodes of coastal uplift only, cannot be
demonstrated beyond all doubt by independent evidence, but it appears the most likely interpretation, given
the geological and active-tectonic context and, what is known about eustatic sea-level fluctuations in the
Mediterranean. Proving that the documented uplifts were abrupt (i.e., arguably coseismic), is equally difficult,
but reasonably expected and rather probable. Five earthquakes in the last ca. 2000 yrs on the coastal fault
zone responsible for the uplift, compare well with historical seismicity and the results of recent on-fault
paleoseismological studies at the nearby Eliki fault zone. Exact amounts of coseismic uplift cannot be
determined precisely, unless the rate of uniform ("regional") non-seismic uplift of Northern Peloponnesus at
the specific part of the Corinth Rift is somehow constrained
Geomorphological, stratigraphic and geochronological evidence of fast Pleistocene coastal uplift in the westernmost part of the Corinth Gulf Rift (Greece)
Rapid extension and active normal faulting in the western extremity of the Corinth Gulf are accompanied by fast coastal uplift.We
investigate Pleistocene uplift west of Aigion, by attempting to date remains of marine terraces and sedimentary sequences by
calcareous nannoplankton and U-series analyses. Net uplift initiated recently, due to abandonment of an older rift-bounding fault
zone and increase in activity on the presently active, coastal fault zone. This change apparently coincides with an abrupt slow down
(or, termination) of secondary fault block tilting within the broader hangingwall block of the older zone, indicated by an angular
unconformity that dates in the early part ofMIS10 ( 390–350 ka BP, preferably, in the earlier part of this period). Net uplift driven
by the coastal zone resulted in the formation of MIS9c (330 ka) and younger terraces. The formation of the unconformity and the
initiation of net uplift coincide temporally with a 300–400 ka unconformity recognized by recent studies in a wide area offshore
Aigion i.e. they could be part of an evolutionary event that affected the entirewestern part of the Corinth Rift or, a large area therein.
Uplift rate estimates at four locations are discussed with reference to the morphotectonic context of differential uplift of secondary
fault blocks, and the context of possible increase in uplift ratewith time. Themost reliable and most useful estimate for uplift rate at
the longitude of the studied transect is 1.74–1.85mm/year (time-averaged estimate for the last 240 ka, based on calcareous
nannoplankton and sequence-stratigraphic interpretation
The Pkn22 Ser/Thr kinase in Nostoc PCC 7120: role of FurA and NtcA regulators and transcript profiling under nitrogen starvation and oxidative stress
International audienceBackground: The filamentous cyanobacterium Nostoc sp. strain PCC 7120 can fix N2 when combined nitrogen is not available. Furthermore, it has to cope with reactive oxygen species generated as byproducts of photosynthesis and respiration. We have previously demonstrated the synthesis of Ser/Thr kinase Pkn22 as an important survival response of Nostoc to oxidative damage. In this study we wished to investigate the possible involvement of this kinase in signalling peroxide stress and nitrogen deprivation. Results: Quantitative RT-PCR experiments revealed that the pkn22 gene is induced in response to peroxide stress and to combined nitrogen starvation. Electrophoretic motility assays indicated that the pkn22 promoter is recognized by the global transcriptional regulators FurA and NtcA. Transcriptomic analysis comparing a pkn22-insertion mutant and the wild type strain indicated that this kinase regulates genes involved in important cellular functions such as photosynthesis, carbon metabolism and iron acquisition. Since metabolic changes may lead to oxidative stress, we investigated whether this is the case with nitrogen starvation. Our results rather invalidate this hypothesis thereby suggesting that the function of Pkn22 under nitrogen starvation is independent of its role in response to peroxide stress. Conclusions: Our analyses have permitted a more complete functional description of Ser/Thr kinase in Nostoc. We have decrypted the transcriptional regulation of the pkn22 gene, and analysed the whole set of genes under the control of this kinase in response to the two environmental changes often encountered by cyanobacteria in their natural habitat: oxidative stress and nitrogen deprivation
Differential Phosphorylation of Ribosomal Proteins in Arabidopsis thaliana Plants during Day and Night
Protein synthesis in plants is characterized by increase in the translation rates for numerous proteins and central metabolic enzymes during the day phase of the photoperiod. The detailed molecular mechanisms of this diurnal regulation are unknown, while eukaryotic protein translation is mainly controlled at the level of ribosomal initiation complexes, which also involves multiple events of protein phosphorylation. We characterized the extent of protein phosphorylation in cytosolic ribosomes isolated from leaves of the model plant Arabidopsis thaliana harvested during day or night. Proteomic analyses of preparations corresponding to both phases of the photoperiod detected phosphorylation at eight serine residues in the C-termini of six ribosomal proteins: S2-3, S6-1, S6-2, P0-2, P1 and L29-1. This included previously unknown phosphorylation of the 40S ribosomal protein S6 at Ser-231. Relative quantification of the phosphorylated peptides using stable isotope labeling and mass spectrometry revealed a 2.2 times increase in the day/night phosphorylation ratio at this site. Phosphorylation of the S6-1 and S6-2 variants of the same protein at Ser-240 increased by the factors of 4.2 and 1.8, respectively. The 1.6 increase in phosphorylation during the day was also found at Ser-58 of the 60S ribosomal protein L29-1. It is suggested that differential phosphorylation of the ribosomal proteins S6-1, S6-2 and L29-1 may contribute to modulation of the diurnal protein synthesis in plants
Role of Plastid Protein Phosphatase TAP38 in LHCII Dephosphorylation and Thylakoid Electron Flow
Regulation of photosynthesis efficiency involves reversible phosphorylation of the light-harvesting complex through the activity of the newly identified phosphatase TAP38
Inactivation of genes coding for mitochondrial Nd7 and Nd9 complex I subunits in Chlamydomonas reinhardtii. Impact of complex I loss on respiration and energetic metabolism.
In Chlamydomonas, unlike in flowering plants, genes coding for Nd7 (NAD7/49kDa) and Nd9 (NAD9/30kDa) core subunits of mitochondrial respiratory-chain complex I are nucleus-encoded. Both genes possess all the features that facilitate their expression and proper import of the polypeptides in mitochondria. By inactivating their expression by RNA interference or insertional mutagenesis, we show that both subunits are required for complex I assembly and activity. Inactivation of complex I impairs the cell growth rate, reduces the respiratory rate, leads to lower intracellular ROS production and lower expression of ROS scavenging enzymes, and is associated to a diminished capacity to concentrate CO2 without compromising photosynthetic capacity.Peer reviewe
Inactivation of genes coding for mitochondrial Nd7 and Nd9 complex I subunits in Chlamydomonas reinhardtii. Impact of complex I loss on respiration and energetic metabolism.
In Chlamydomonas, unlike in flowering plants, genes coding for Nd7 (NAD7/49kDa) and Nd9 (NAD9/30kDa) core subunits of mitochondrial respiratory-chain complex I are nucleus-encoded. Both genes possess all the features that facilitate their expression and proper import of the polypeptides in mitochondria. By inactivating their expression by RNA interference or insertional mutagenesis, we show that both subunits are required for complex I assembly and activity. Inactivation of complex I impairs the cell growth rate, reduces the respiratory rate, leads to lower intracellular ROS production and lower expression of ROS scavenging enzymes, and is associated to a diminished capacity to concentrate CO2 without compromising photosynthetic capacity.Peer reviewe
Evaluation and mangement of fungal risk in cystic fibrosis: first results of a national French study
Date du colloque : 06/2009</p
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