DNA methylation plays a vital role in the regulation of gene expression in response to environmental stress. However, little is known about the effect of DNA methylation on the cassava polyploidy. In the present study...DNA methylation plays a vital role in the regulation of gene expression in response to environmental stress. However, little is known about the effect of DNA methylation on the cassava polyploidy. In the present study, methylation-sensitive amplified polymorphisms （MSAP） were used to investigate DNA methylation profiles of cassava polyploidy following cold treatment to identify candidate genes involved in response to cold stress. The result showed that the genome-wide DNA methylation polymorphisms accounted for 34.02%-42.56% in SC8 and its autotetraploid exposed to 5 ~C for 2, 8, 24 and 48 h, respectively. The methylation levels of SC8 at 2 h-cold stress were the highest during 48h under cold treatments. With the time extension within 48 h under cold stress, the methylation levels gradually decreased to the same level as the control but DNA methylation levels of cassava autotetraploid were stable within 48 h. For future analysis of the methylation extent, the cold stress induced more DNA methylation than demethylation in SC8, where DNA methylation was consistent with demethylation in its autotetraploid. The expression analysis demonstrated increase in the transcription of one methylated gene and decrease in the transcription of two demethylated genes. The results revealed that gene methylations in specific sites would be a rapidly epigenetic response to cold stress, further elucidating the methylation functions in its autotetraploid.展开更多
In this article,we relocated the seismic source location of the earthquakes in the Muli area of Sichuan,inverted the focal mechanism of the larger earthquakes and analyzed the relationship between the water level of t...In this article,we relocated the seismic source location of the earthquakes in the Muli area of Sichuan,inverted the focal mechanism of the larger earthquakes and analyzed the relationship between the water level of the Jinping reservoir and the frequency of the earthquake swarm. The results show that:( 1) The epicenters of the relocated small earthquake swarms are distributed in a seismic zone,and the earthquake focal depths were in the range of 0- 12 km.( 2) By analyzing the earthquake swarm spatial distribution,we found that the swarms were generated by one branch fault on the west of Xiaojinhe fault.( 3) The focal mechanism of the three earthquakes with magnitude greater than 4. 0 is significantly different,with the shallow source thrust events affected by vertical stress,and the strike-slip events are related to regional stress tectonic activity.展开更多
The geographical location of Qaidam Basin corresponds toN36°05′-38°10′ and E90°10′-98°05′. The thickness of the Quaternary deposits in the basin reaches 2000-3000 m. This paper deals mainly wit...The geographical location of Qaidam Basin corresponds toN36°05′-38°10′ and E90°10′-98°05′. The thickness of the Quaternary deposits in the basin reaches 2000-3000 m. This paper deals mainly with the aspect of paleoclimate change of the basin. The approach used for the study consisted of (1) establishing the paleoclimate curve of the basin according to the climate indices, including the spore-pollen statistics, carbonate content and δ18O, obtained from the samples of the 760 m continuously-cored exploration holes sited in the basin, (2) comparing the paleoclimate curve with the natural gamma-logs of the same exploration holes, and (3) determining the paleoclimatic changes in the last 2.85 Ma on the basis of detailed geochronological calculations. These results are extremely important for comparison with the δ18O-based climate curve derived from the ODP659 in the Atlantic Ocean and with the cycles of paleosol in the Chinese loess.展开更多
Origin of dolostone remained a controversial subject, although numerous dolomitization models had been proposed to date. Because of the dolomitization＇s potential to be hydrocarbon reservoirs, one debatable issue was...Origin of dolostone remained a controversial subject, although numerous dolomitization models had been proposed to date. Because of the dolomitization＇s potential to be hydrocarbon reservoirs, one debatable issue was the role of dolomitization in porosity construction or destruction. Based upon case studies of dolostone reservoirs in various geological settings such as evaporative tidal flat （Ordos Basin, NW China）, evaporative platform （Sichuan Basin, SW China）, and burial and hydrothermal diagenesis （Tarim Basin, NW China）, here we systematically discuss the origin of porosity in dolostone reservoirs. Contrary to traditional concepts, which regarded dolomitization as a significant mechanism for porosity creation, we found two dominant factors controlling reservoir development in dolostones, i.e., porosity inherited from precursor carbonates and porosity resulted from post-dolomitization dissolution. Actually, dolomitization rarely had a notable effect on porosity creation but rather in many cases destroyed pre-existing porosity such as saddle dolostone precipitation in vugs and fractures. Porosity in dolostones associated with evaporative tidal flat or evaporative platform was generally created by subaerial dissolution of evaporites and/or undolomitized components. Porosity in burial dolostones was inherited mostly from precursor carbonates, which could be enlarged due to subsequent dissolution. Intercrystalline porosity in hydrothermal dolostones was either formed during dolo- mitization or inherited from precursor carbonates, whereas dissolution-enlarged intercrystalline pores and/or vugs were usually interpreted to be the result of hydrothermai alteration. These understandings on dolostone porosity shed light on reservoir pre- diction. Dolostone reservoirs associated with evaporative tidal flat were laterally distributed as banded or quasi-stratified shapes in evaporite-bearing dolostones, and vertically presented as multi-interval patterns on tops of shallowing-upward cycles Dolostone reservoirs associated with evaporative platform commonly occurred along epiplatforms or beneath evaporite beds, and vertically presented as multi-interval patterns in dolostones and/or evaporite-bearing dolostones of reef/shoal facies. Con- strained by primary sedimentary facies, burial dolostone reservoirs were distributed in dolomitized, porous sediments of reef/shoal facies, and occurred vertically as multi-intervai patterns in crystalline dolostones on tops of shallowing-upward cy- cles. Hydrothermal dolomitization was obviously controlled by conduits （e.g., faults, unconformities）, along which lenticular reservoirs could develop.展开更多
文摘DNA methylation plays a vital role in the regulation of gene expression in response to environmental stress. However, little is known about the effect of DNA methylation on the cassava polyploidy. In the present study, methylation-sensitive amplified polymorphisms （MSAP） were used to investigate DNA methylation profiles of cassava polyploidy following cold treatment to identify candidate genes involved in response to cold stress. The result showed that the genome-wide DNA methylation polymorphisms accounted for 34.02%-42.56% in SC8 and its autotetraploid exposed to 5 ~C for 2, 8, 24 and 48 h, respectively. The methylation levels of SC8 at 2 h-cold stress were the highest during 48h under cold treatments. With the time extension within 48 h under cold stress, the methylation levels gradually decreased to the same level as the control but DNA methylation levels of cassava autotetraploid were stable within 48 h. For future analysis of the methylation extent, the cold stress induced more DNA methylation than demethylation in SC8, where DNA methylation was consistent with demethylation in its autotetraploid. The expression analysis demonstrated increase in the transcription of one methylated gene and decrease in the transcription of two demethylated genes. The results revealed that gene methylations in specific sites would be a rapidly epigenetic response to cold stress, further elucidating the methylation functions in its autotetraploid.
基金sponsored by the Regular Project of Earthquake Monitoring and Prediction in 2016(16C23ZX327)
文摘In this article,we relocated the seismic source location of the earthquakes in the Muli area of Sichuan,inverted the focal mechanism of the larger earthquakes and analyzed the relationship between the water level of the Jinping reservoir and the frequency of the earthquake swarm. The results show that:( 1) The epicenters of the relocated small earthquake swarms are distributed in a seismic zone,and the earthquake focal depths were in the range of 0- 12 km.( 2) By analyzing the earthquake swarm spatial distribution,we found that the swarms were generated by one branch fault on the west of Xiaojinhe fault.( 3) The focal mechanism of the three earthquakes with magnitude greater than 4. 0 is significantly different,with the shallow source thrust events affected by vertical stress,and the strike-slip events are related to regional stress tectonic activity.
基金NSFC (Grant No. 49871002) and under the auspices of the Chinese National Key Project for Basic Research on Tibetan Plateau (KZ951-A1-204, KZ95T-06).
文摘The geographical location of Qaidam Basin corresponds toN36°05′-38°10′ and E90°10′-98°05′. The thickness of the Quaternary deposits in the basin reaches 2000-3000 m. This paper deals mainly with the aspect of paleoclimate change of the basin. The approach used for the study consisted of (1) establishing the paleoclimate curve of the basin according to the climate indices, including the spore-pollen statistics, carbonate content and δ18O, obtained from the samples of the 760 m continuously-cored exploration holes sited in the basin, (2) comparing the paleoclimate curve with the natural gamma-logs of the same exploration holes, and (3) determining the paleoclimatic changes in the last 2.85 Ma on the basis of detailed geochronological calculations. These results are extremely important for comparison with the δ18O-based climate curve derived from the ODP659 in the Atlantic Ocean and with the cycles of paleosol in the Chinese loess.
基金supported by Major National Science and Technology Project of China(Grant No.2011ZX05004-02)
文摘Origin of dolostone remained a controversial subject, although numerous dolomitization models had been proposed to date. Because of the dolomitization＇s potential to be hydrocarbon reservoirs, one debatable issue was the role of dolomitization in porosity construction or destruction. Based upon case studies of dolostone reservoirs in various geological settings such as evaporative tidal flat （Ordos Basin, NW China）, evaporative platform （Sichuan Basin, SW China）, and burial and hydrothermal diagenesis （Tarim Basin, NW China）, here we systematically discuss the origin of porosity in dolostone reservoirs. Contrary to traditional concepts, which regarded dolomitization as a significant mechanism for porosity creation, we found two dominant factors controlling reservoir development in dolostones, i.e., porosity inherited from precursor carbonates and porosity resulted from post-dolomitization dissolution. Actually, dolomitization rarely had a notable effect on porosity creation but rather in many cases destroyed pre-existing porosity such as saddle dolostone precipitation in vugs and fractures. Porosity in dolostones associated with evaporative tidal flat or evaporative platform was generally created by subaerial dissolution of evaporites and/or undolomitized components. Porosity in burial dolostones was inherited mostly from precursor carbonates, which could be enlarged due to subsequent dissolution. Intercrystalline porosity in hydrothermal dolostones was either formed during dolo- mitization or inherited from precursor carbonates, whereas dissolution-enlarged intercrystalline pores and/or vugs were usually interpreted to be the result of hydrothermai alteration. These understandings on dolostone porosity shed light on reservoir pre- diction. Dolostone reservoirs associated with evaporative tidal flat were laterally distributed as banded or quasi-stratified shapes in evaporite-bearing dolostones, and vertically presented as multi-interval patterns on tops of shallowing-upward cycles Dolostone reservoirs associated with evaporative platform commonly occurred along epiplatforms or beneath evaporite beds, and vertically presented as multi-interval patterns in dolostones and/or evaporite-bearing dolostones of reef/shoal facies. Con- strained by primary sedimentary facies, burial dolostone reservoirs were distributed in dolomitized, porous sediments of reef/shoal facies, and occurred vertically as multi-intervai patterns in crystalline dolostones on tops of shallowing-upward cy- cles. Hydrothermal dolomitization was obviously controlled by conduits （e.g., faults, unconformities）, along which lenticular reservoirs could develop.
