Phosphorylation by Cdk1 Increases the Binding of Eg5 to Microtubules In Vitro and in Xenopus Egg Extract Spindles

BACKGROUND:Motor proteins from the kinesin-5 subfamily play an essential role in spindle assembly during cell division of most organisms. These motors crosslink and slide microtubules in the spindle. Kinesin-5 motors are phosphorylated at a conserved site by Cyclin-dependent kinase 1 (Cdk1) during mitosis. Xenopus laevis kinesin-5 has also been reported to be phosphorylated by Aurora A in vitro. METHODOLOGY/PRINCIPAL FINDINGS:We investigate here the effect of these phosphorylations on kinesin-5 from Xenopus laevis, called Eg5. We find that phosphorylation at threonine 937 in the C-terminal tail of Eg5 by Cdk1 does not affect the velocity of Eg5, but strongly increases its binding to microtubules assembled in buffer. Likewise, this phosphorylation promotes binding of Eg5 to microtubules in Xenopus egg extract spindles. This enhancement of binding elevates the amount of Eg5 in spindles above a critical level required for bipolar spindle formation. We find furthermore that phosphorylation of Xenopus laevis Eg5 by Aurora A at serine 543 in the stalk is not required for spindle formation. CONCLUSIONS/SIGNIFICANCE:These results show that phosphorylation of Eg5 by Cdk1 has a direct effect on the interaction of this motor with microtubules. In egg extract, phosphorylation of Eg5 by Cdk1 ensures that the amount of Eg5 in the spindle is above a level that is required for spindle formation. This enhanced targeting to the spindle appears therefore to be, at least in part, a direct consequence of the enhanced binding of Eg5 to microtubules upon phosphorylation by Cdk1. These findings advance our understanding of the regulation of this essential mitotic motor protein

WMO assessment of weather and climate mortality extremes : lightning, tropical cyclones, tornadoes, and hail

A World Meteorological Organization (WMO) Commission for Climatology international panel was convened to examine and assess the available evidence associated with five weather-related mortality extremes: 1) lightning (indirect), 2) lightning (direct), 3) tropical cyclones, 4) tornadoes, and 5) hail. After recommending for acceptance of only events after 1873 (the formation of the predecessor of the WMO), the committee evaluated and accepted the following mortality extremes: 1) ''highest mortality (indirect strike) associated with lightning'' as the 469 people killed in a lightning-caused oil tank fire in Dronka, Egypt, on 2 November 1994; 2) ''highest mortality directly associated with a single lightning flash'' as the lightning flash that killed 21 people in a hut in Manica Tribal Trust Lands, Zimbabwe (at time of incident, eastern Rhodesia), on 23 December 1975; 3) ''highest mortality associated with a tropical cyclone'' as the Bangladesh (at time of incident, East Pakistan) cyclone of 12-13 November 1970 with an estimated death toll of 300 000 people| 4) ''highest mortality associated with a tornado'' as the 26 April 1989 tornado that destroyed the Manikganj district, Bangladesh, with an estimated death toll of 1300 individuals| and 5) ''highest mortality associated with a hailstorm'' as the storm occurring near Moradabad, India, on 30 April 1888 that killed 246 people. These mortality extremes serve to further atmospheric science by giving baseline mortality values for comparison to future weather-related catastrophes and also allow for adjudication of new meteorological information as it becomes available.https://www.ametsoc.org/ams/index.cfm/publications/journals/weather-climate-and-society2018-01-30hj2017Geography, Geoinformatics and Meteorolog

Globalna analiza atmosferskih refrakcijskih profilov iz prekrivanj radijskih signalov COMSIC GPS

Atmospheric refractivity is a function of temperature, pressure and water vapor. The refractivity retrieved from the GNSS radio occultation soundings has fine vertical resolution and high accuracy, so it can be used to improve the accuracy of numerical weather prediction models and in climate and meteorological research. This study evaluates differences of refractivity from the COSMIC against radiosondes (RS) at different atmospheric levels, latitudes and seasons. Then temporal and global spatial distribution patterns of the COSMIC refractivity are analyzed at the atmospheric levels of 925 and 300 hPa. The results indicate that the COSMIC and RS refractivities are in generally good agreement. The differences between COSMIC and RS refractivity decrease with increasing height in the troposphere above 300 hPa, and the differences are very small above the tropopause. The COSMIC-RS differences exhibit distinct latitudinal and seasonal variation.The global COSMIC refractivity at 925 hPa is the highest in the tropics, and it decreases with increasing latitude in the NH and SH. However, the refractivity at the atmospheric levels of 300 hPa is just the opposite. Refractivity anomalies relative to the annual mean values in January and July are significant, whereas the differences are not as large in the transitional seasons of April and October.Atmosferska refrakcija je odvisna od temperature, tlaka in vodne pare. Iz GNSS ocenjena refrakcija ima dovolj dobro vertikalno ločljivost in točnost, da jo lahko vključimo v numerične modele napovedi vremena ter uporabimo v meteoroloških in klimatskih raziskavah. V študiji smo ovrednotili razlike med modelom refrakcije, pridobljenim iz sistema COSMIC, in izračuni iz podatkov vertikalne radiosondaže, in sicer za različne višine, geografske širine in letne čase. Analizirali smo časovne in globalne prostorske porazdelitvene vzorce atmosferske refrakcije na podlagi podatkov COSMIC za atmosferske ravni, kjer zračni tlak znaša 925 hPa in 300 hPa. Rezultati so pokazali, da je ocenjena refrakcija v splošnem podobna oceni iz podatkov radiosond. Razlika se značilno manjša z višino, ko je v troposferi tlak nad 300 hPa, nad tropopavzo pa so razlike komaj še zaznavne. Izrazite razlike med oceno refrakcije iz podatkov COSMOS oziroma podatkov, pridobljenih z radiosondami, se kažejo s spreminjanjem geografske širine in z letnim časom. Globalna refrakcija COSMIC na višini, kjer je tlak 825 hPa, je najvišja v tropskem pasu ter se manjša proti severni in južni hemisferi. V atmosferi na višini, kjer je tlak 300 hPa, je z refrakcijo ravno nasprotno. Anomalije refrakcije glede na srednjo letno vrednost so večje v januarju in juliju, manjše pa v aprilu in oktobru

Primerjava vsebnosti vodne pare v stolpcu zraka na podlagi radiosondaže ter opazovanj GPS in fotometra

The atmospheric precipitable water vapour (PWV) plays a crucial role in the hydrological cycle and energy transfer on a global scale. Radiosonde (RS), sunphotometer (SP) and GPS (as well as broader GNSS) receivers have gradually been the principal instruments for ground-based PWV observation. This study first co-locates the observation stations configured the three instruments in the globe and in three typical latitudinal climatic regions respectively, then the PWV data from the three instruments are matched each other according to the observing times. After the outliers are removed from the matched data pairs, the PWV intercomparisons for any two instruments are performed. The results show that the PWV estimates from any two instruments have a good agreement with very high correlation coefficients. The latitude and climate have no significant influence on the PWV measurements from the three instruments, indicating that the instruments are very stable and depend on their performance. The PWV differences of any two instruments display the normal distribution, indicating nonsystematic biases among the two PWV datasets. The relative differences between SP and GPS are the smallest, the middle between SP and RS, and those between GPS and RS are the largest. This study will be useful to promote GPS (GNSS) and SP PWV to be a substitute for RS PWV as a benchmark because of their high temporal resolutions.Atmosfeska vsebnost vodne pare v stolpcu zraka PWV (angl. precipitable water vapor) je globalno izrednega pomena tako z vidika hidriloškega kroženja kot prenosa energije. Radiosonde, sončni fotometer in sprejemniki GPS (pa tudi širše GNSS) so postali temeljni instrumenti za terestrično opazovanje PVW. Pri študiji smo imeli na voljo vse tri instrumente, ki so bili hkrati nameščeni na opazovalnih postajah, ki so geografsko pokrivale tri tipične podnebne pasove. Podatke PWV z vseh instrumentov smo združili glede na čas opazovanj. Po tem, ko smo odstranili izstopajoča opazovanja, smo izvedli primerjavo vrendosti PWV za vsak par opazovanj različnih instrumentov. Ugotavljamo, da geografska širina in podnebje ne vplivata pomembneje na vrednosti PWV, pridobljene z radiosondažo, z opazovanji GPS ali opazovanji s fotometrom. Odstopanja v vrednostih PWV za katerikoli par instrumentov so normalno porazdeljena, kar pomeni, da v podatkih PWV ni sistematičnih pogreškov. Relativne razlike med vrednostmi PWV, pridobljenimi z radiosondažo in opazovanji GPS, so najmanjše, nekoliko večje so razlike med vrendostmi, pridobljenimi z radiosondažo in fotometrijo, največje razlike pa so med vrednostmi, pridobljenimi z opazovanji GPS in radiosondažo. Študija je zanimiva za spodbujanje uporabe sprejemnikov GPS (GNSS) in fotometrov za določanje vrednosti PWV namesto radiosondaže, saj takšna opazovanja omogočajo tudi visoko časovno ločljivost

Annual and Seasonal Precipitation and Their Extremes over the Tibetan Plateau and Its Surroundings in 1963–2015

Based on daily precipitation data from 115 climate stations, seasonal and annual precipitation and their extremes over the Tibetan Plateau and its surroundings (TPS) in 1963–2015 are investigated. There exists a clear southeast-northwest gradient in precipitation and extreme daily precipitation but an opposite pattern for the consecutive dry days (CDDs). The wet southeast is trending dry while the dry center and northwest are trending wet in 1963–2015. Correspondingly, there is a drying tendency over the wet basins in the southeast and a wetting tendency over the dry and semi-dry basins in the center and northwest in summer, which will affect the water resources in the corresponding areas. The increase (decrease) in precipitation tends to correspond to the increase (decrease) in maximum daily precipitation but the decrease (increase) in CDDs. Extreme precipitation events with 20-year, 50-year, 100-year, and 200-year recurrence occurred frequently in the past decades especially in the 1980s. The greatest extreme precipitation events tend to occur after the late 1990s and in the southeastern TPS. The ERA5 reanalysis and climate system indices reveal that (1) decreased moisture transports to the southeast in summer due to the weakening of the summer monsoons and the East Asian westerly jet; (2) increased moisture transports to the center in winter due to the strengthening of the winter westerly jet and north Atlantic oscillation; and (3) decreased instability over the southeast thus suppressing precipitation and increased instability over the northwest thus promoting precipitation. All these are conducive to the drying trends in the southeast and the wetting trends in the center

Characteristics of Dry-Wet Climate Change in China during the Past 60 Years and Its Trends Projection

Based on the homogenized daily data of 2255 meteorological stations during the past 60 years from 1961 to 2020, the potential evapotranspiration was calculated using the revised FAO56 Penman–Monteith model, and then the annual AI (aridity index, the ratio of annual potential evapotranspiration to annual precipitation) was employed to analyze the dry-wet climate change in China. The GCM models’ prediction data was used to analyze the possible trends of dry-wet climate in China by the end of this century. The results showed that in the past 60 years, the climate in China was getting wetter, especially in the western regions of China, including Xinjiang, western Qinghai, Gansu, western Inner Mongolia, and northwestern Tibet. In the last 10 years, China’s climate has become more humid. Compared with the 1960s, the total area of aridity has decreased by about 650,000 square kilometers. The changes of different climate zones have regional and periodical characteristics. There was a tendency to get wet periods in all four seasons, especially in summer. Analysis of GCM model projection data shows that by the end of this century, the climate in China would have a general trend of becoming drier. The drier regions are mainly located in the central and eastern parts of China, while the western regions of China continue to maintain the wetting trends. In the case of high emissions, the trends of drying in the central and eastern and wetting in the west are more significant than in the case of medium emission