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1. chinaXiv:202106.00015 [pdf]

Spatiotemporal analysis of drought variability based on the standardized precipitation evapotranspiration index in the Koshi River Basin, Nepal

Nirmal M DAHAL; XIONG Donghong; Nilhari NEUPANE; Belayneh YIGEZ; ZHANG Baojun; YUAN Yong; Saroj KOIRALA; LIU Lin; FANG Yiping
Subjects: Geosciences >> Geography

Drought is an inevitable condition with negative impacts in the agricultural and climatic sectors, especially in developing countries. This study attempts to examine the spatial and temporal characteristics of drought and its trends in the Koshi River Basin (KRB) in Nepal, using the standardized precipitation evapotranspiration index (SPEI) over the period from 1987 to 2017. The Mann-Kendall test was used to explore the trends of the SPEI values. The study illustrated the increasing annual and seasonal drought trends in the KRB over the study period. Spatially, the hill region of the KRB showed substantial increasing drought trends at the annual and seasonal scales, especially in summer and winter. The mountain region also showed a significant increasing drought trend in winter. The drought characteristic analysis indicated that the maximum duration, intensity, and severity of drought events were observed in the KRB after 2000. The Terai region presented the highest drought frequency and intensity, while the hill region presented the longest maximum drought duration. Moreover, the spatial extent of drought showed a significant increasing trend in the hill region at the monthly (drought station proportion of 7.6%/10a in August), seasonal (drought station proportion of 7.2%/10a in summer), and annual (drought station proportion of 6.7%/10a) scales. The findings of this study can assist local governments, planners, and project implementers in understanding drought and developing appropriate mitigation strategies to cope with its impacts.

submitted time 2021-06-04 From cooperative journals:《Journal of Arid Land》 Hits2757Downloads384 Comment 0

2. chinaXiv:201605.01453 [pdf]

Crystal structure of the catalytic subunit of magnesium chelatase

Chen, Xuemin; Pu, Hua; Fang, Ying; Wang, Xiao; Zhao, Shun; Dai, Huai-En; Liu, Lin; Chen, Xuemin; Pu, Hua; Fang, Ying; Wang, Xiao; Zhao, Shun; Lin, Yajing; Gong, Weimin; Zhang, Min; Gong, Weimin
Subjects: Biology >> Biophysics

Tetrapyrroles, including haem and chlorophyll, play vital roles for various biological processes, such as respiration and photosynthesis, and their biosynthesis is critical for virtually all organisms. In photosynthetic organisms, magnesium chelatase (MgCh) catalyses insertion of magnesium into the centre of protoporphyrin IX, the branch-point precursor for both haem and chlorophyll, leading tetrapyrrole biosynthesis into the magnesium branch1,2. This reaction needs a cooperated action of the three subunits of MgCh: the catalytic subunit ChlH and two AAA(+) subunits, ChlI and ChlD ( refs 3-5). To date, the mechanism of MgCh awaits further elucidation due to a lack of high-resolution structures, especially for the similar to 150 kDa catalytic subunit. Here we report the crystal structure of ChlH from the photosynthetic cyanobacterium Synechocystis PCC 6803, solved at 2.5 angstrom resolution. The active site is buried deeply inside the protein interior, and the surrounding residues are conserved throughout evolution. This structure helps to explain the loss of function reported for the cch and gun5 mutations of the ChlH subunit, and to provide the molecular basis of substrate channelling during the magnesium-chelating process. The structure advances our understanding of the holoenzyme of MgCh, a metal chelating enzyme other than ferrochelatase.

submitted time 2016-05-12 Hits1825Downloads973 Comment 0

3. chinaXiv:201605.01352 [pdf]

Diacylglycerol Guides the Hopping of Clathrin-Coated Pits along Microtubules for Exo-Endocytosis Coupling

Yuan, Tianyi; Liu, Lin; Wei, Lisi; Zhao, Shiqun; Zheng, Xiaolu; Huang, Xiaoshuai; Xie, Lihan; Zong, Weijian; Yang, Lu; Liu, Yanmei; Chen, Liangyi; Yuan, Tianyi; Liu, Lin; Wei, Lisi; Zhao, Shiqun; Zheng, Xiaolu; Huang, Xiaoshuai; Xie, Lihan; Zong, Weijian; Yang, Lu
Subjects: Biology >> Biophysics >> Cell Biology

Many receptor-mediated endocytic processes are mediated by constitutive budding of clathrin-coated pits (CCPs) at spatially randomized sites before slowly pinching off from the plasma membrane (60100 s). In contrast, clathrin-mediated endocytosis (CME) coupled with regulated exocytosis in excitable cells occurs at peri-exocytic sites shortly after vesicle fusion (similar to 10 s). The molecular mechanism underlying this spatiotemporal coupling remains elusive. We show that coupled endocytosis makes use of preformed CCPs, which hop to nascent fusion sites nearby following vesicle exocytosis. A dynamic cortical microtubular network, anchored at the cell surface by the cytoplasmic linker-associated protein on microtubules and the LL5 beta/ELKS complex on the plasma membrane, provides the track for CCP hopping. Local diacylglycerol gradients generated upon exocytosis guide the direction of hopping. Overall, the CCP-cytoskeleton-lipid interaction demonstrated here mediates exocytosis-coupled fast recycling of both plasma membrane and vesicular proteins, and it is required for the sustained exocytosis during repetitive stimulations.

submitted time 2016-05-11 Hits1489Downloads874 Comment 0

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