An RNA degradation machine sculpted by Ro autoantigen and noncoding RNA.

Many bacteria contain an ortholog of the Ro autoantigen, a ring-shaped protein that binds noncoding RNAs (ncRNAs) called Y RNAs. In the only studied bacterium, Deinococcus radiodurans, the Ro ortholog Rsr functions in heat-stress-induced ribosomal RNA (rRNA) maturation and starvation-induced rRNA decay. However, the mechanism by which this conserved protein and its associated ncRNAs act has been obscure. We report that Rsr and the exoribonuclease polynucleotide phosphorylase (PNPase) form an RNA degradation machine that is scaffolded by Y RNA. Single-particle electron microscopy, followed by docking of atomic models into the reconstruction, suggests that Rsr channels single-stranded RNA into the PNPase cavity. Biochemical assays reveal that Rsr and Y RNA adapt PNPase for effective degradation of structured RNAs. A Ro ortholog and ncRNA also associate with PNPase in Salmonella Typhimurium. Our studies identify another ribonucleoprotein machine and demonstrate that ncRNA, by tethering a protein cofactor, can alter the substrate specificity of an enzyme.

Transfer RNA halves are found as nicked tRNAs in cells: evidence that nicked tRNAs regulate expression of an RNA repair operon.

Transfer RNA fragments are proposed to regulate numerous processes in eukaryotes, including translation inhibition, epigenetic inheritance, and cancer. In the bacterium Salmonella enterica serovar Typhimurium, 5' tRNA halves ending in 2',3' cyclic phosphate are proposed to bind the RtcR transcriptional activator, resulting in transcription of an RNA repair operon. However, since 5' and 3' tRNA halves can remain base paired after cleavage, the 5' tRNA halves could potentially bind RtcR as nicked tRNAs. Here we report that nicked tRNAs are ligands for RtcR. By isolating RNA from bacteria under conditions that preserve base pairing, we show that many tRNA halves are in the form of nicked tRNAs. Using a circularly permuted tRNA that mimics a nicked tRNA, we show that nicked tRNA ending in 2',3' cyclic phosphate is a better ligand for RtcR than the corresponding 5' tRNA half. In human cells, we show that some tRNA halves similarly remain base paired as nicked tRNAs following cleavage by anticodon nucleases. Our work supports a role for the RNA repair operon in repairing nicked tRNAs and has implications for the functions proposed for tRNA fragments in eukaryotes.

The Bacterial Ro60 Protein and Its Noncoding Y RNA Regulators.

Ro60 ribonucleoproteins (RNPs), composed of the ring-shaped Ro 60-kDa (Ro60) protein and noncoding RNAs called Y RNAs, are present in all three domains of life. Ro60 was first described as an autoantigen in patients with rheumatic disease, and Ro60 orthologs have been identified in 3% to 5% of bacterial genomes, spanning the majority of phyla. Their functions have been characterized primarily in Deinococcus radiodurans, the first sequenced bacterium with a recognizable ortholog. In D. radiodurans, the Ro60 ortholog enhances the ability of 3'-to-5' exoribonucleases to degrade structured RNA during several forms of environmental stress. Y RNAs are regulators that inhibit or allow the interactions of Ro60 with other proteins and RNAs. Studies of Ro60 RNPs in other bacteria hint at additional functions, since the most conserved Y RNA contains a domain that is a close tRNA mimic and Ro60 RNPs are often encoded adjacent to components of RNA repair systems.

Spatially resolved visualization of reprogrammed metabolism in hepatocellular carcinoma by mass spectrometry imaging.

BACKGROUND: Metabolic reprogramming refers to tumor-associated metabolic alterations during tumorigenesis and has been regarded as one of the most important features of cancer. Profiling the altered metabolites and lipids in hepatocellular carcinoma with spatial signature will not only enhance our understanding of tumor metabolic reprogramming, but also offer potential metabolic liabilities that might be exploited for hepatocellular carcinoma therapy. METHODS: We perform matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) analysis on both hepatocellular carcinoma xenograft mouse model and hepatocellular carcinoma patients. Discriminatory metabolites that altered during the development of hepatocellular carcinoma are screened and imaged in xenograft mouse model and are further validated in 21 hepatocellular carcinoma patients. RESULTS: We discover stepwise metabolic alterations and progressively increasing metabolic heterogeneity during the growth of hepatocellular carcinoma. Arginine and its metabolites spermine and spermidine, choline and phosphatidylcholine metabolism, and fatty acids were found to be significantly reprogrammed in hepatocellular carcinoma tissues. CONCLUSIONS: The spatially resolved profiling of the metabolites and lipids in highly heterogeneous hepatocellular carcinoma tissue will contribute to obtaining precise metabolic information for the understanding of tumor metabolic reprogramming.

A Cytological Atlas of the Human Liver Proteome from PROTEOMESKY-LIVERHu 2.0, a Publicly Available Database.

The liver plays a unique role as a metabolic center of the body, and also performs other important functions such as detoxification and immune response. Here, we establish a cell type-resolved healthy human liver proteome including hepatocytes (HCs), hepatic stellate cells (HSCs), Kupffer cells (KCs), and liver sinusoidal endothelial cells (LSECs) by high-resolution mass spectrometry. Overall, we quantify total 8354 proteins for four cell types and over 6000 proteins for each cell type. Analysis of this data set and regulatory pathway reveals the cellular labor division in the human liver follows the pattern that parenchymal cells make the main components of pathways, but nonparenchymal cells trigger these pathways. Human liver cells show some novel molecular features: HCs maintain KCs and LSECs homeostasis by producing cholesterol and ketone bodies; HSCs participate in xenobiotics metabolism as an agent deliverer; KCs and LSECs mediate immune response through MHC class II-TLRs and MHC class I-TGFß cascade, respectively; and KCs play a central role in diurnal rhythms regulation through sensing diurnal IGF and temperature flux. Together, this work expands our understandings of liver physiology and provides a useful resource for future analyses of normal and diseased livers.

Deletion of the rnl gene encoding a nick-sealing RNA ligase sensitizes Deinococcus radiodurans to ionizing radiation.

Deinococcus radiodurans RNA ligase (DraRnl) seals 3΄-OH/5΄-PO4 nicks in duplex nucleic acids in which the 3΄-OH nick terminus consists of two or more ribonucleotides. DraRnl exemplifies a widely distributed Rnl5 family of nick-sealing RNA ligases, the physiological functions of which are uncharted. Here we show via gene knockout that whereas DraRnl is inessential for growth of D. radiodurans, its absence sensitizes the bacterium to killing by ionizing radiation (IR). DraRnl protein is present in exponentially growing and stationary phase cells, but is depleted during the early stages of recovery from 10 kGy of IR and subsequently replenished during the late phase of post-IR genome reassembly. Absence of DraRnl elicts a delay in reconstitution of the 10 kGy IR-shattered D. radiodurans replicons that correlates with the timing of DraRnl replenishment in wild-type cells. Complementation with a catalytically dead mutant highlights that nick sealing activity is important for the radioprotective function of DraRnl. Our findings suggest a scenario in which DraRnl acts at genomic nicks resulting from gap-filling by a ribonucleotide-incorporating repair polymerase.

Effect of Palliative Care for Patients with Heart Failure.

Palliative care might be beneficial to heart failure. However, the results remain controversial. We conducted a systematic review and meta-analysis to explore the effect of palliative care on heart failure.PubMed, Embase, Web of Science, EBSCO, and Cochrane library databases were systematically searched. Randomized controlled trials (RCTs) assessing the effect of palliative care versus usual care on heart failure were included. Two investigators independently searched articles, extracted data, and assessed the quality of included studies. The primary outcome was readmission. Meta-analysis was performed using random-effect model.Five RCTs involving 545 patients were included in the meta-analysis. Overall, compared with control intervention, palliative care intervention was found to significantly reduce the readmission [Std. mean difference = 0.79; 95% confidence intervals (CI) = 0.23 to 1.35; P = 0.006], Edmonton Symptom Assessment Scale (ESAS) (Std. mean difference = -2.5; 95% CI = -4.39 to -0.62; P = 0.009), and PHQ-9 (Std. mean difference = -1.16; 95% CI = -1.73 to -0.58; P < 0.005), as well as improve heart failure questionnaire (Std. mean difference = 4.46; 95% CI = 3.44 to 5.47; P < 0.005), but had no influence on mortality (RR = 1.54; 95% CI = 0.80 to 2.96; P = 0.19) and quality of life questionnaire (Std. mean difference = 1.81; 95% CI = -0.14 to 3.77; P = 0.07).Compared with control intervention, palliative care intervention was found to significantly reduce readmission, ESAS, PHQ-9, and improve heart failure questionnaire, but showed no influence on mortality and quality of life questionnaire in patients with heart failure.

Bacterial noncoding Y RNAs are widespread and mimic tRNAs.

Many bacteria encode an ortholog of the Ro60 autoantigen, a ring-shaped protein that is bound in animal cells to noncoding RNAs (ncRNAs) called Y RNAs. Studies in Deinococcus radiodurans revealed that Y RNA tethers Ro60 to polynucleotide phosphorylase, specializing this exoribonuclease for structured RNA degradation. Although Ro60 orthologs are present in a wide range of bacteria, Y RNAs have been detected in only two species, making it unclear whether these ncRNAs are common Ro60 partners in bacteria. In this study, we report that likely Y RNAs are encoded near Ro60 in >250 bacterial and phage species. By comparing conserved features, we discovered that at least one Y RNA in each species contains a domain resembling tRNA. We show that these RNAs contain nucleotide modifications characteristic of tRNA and are substrates for several enzymes that recognize tRNAs. Our studies confirm the importance of Y RNAs in bacterial physiology and identify a new class of ncRNAs that mimic tRNA.

Tissue-Based Proteogenomics Reveals that Human Testis Endows Plentiful Missing Proteins.

Investigations of missing proteins (MPs) are being endorsed by many bioanalytical strategies. We proposed that proteogenomics of testis tissue was a feasible approach to identify more MPs because testis tissues have higher gene expression levels. Here we combined proteomics and transcriptomics to survey gene expression in human testis tissues from three post-mortem individuals. Proteins were extracted and separated with glycine- and tricine-SDS-PAGE. A total of 9597 protein groups were identified; of these, 166 protein groups were listed as MPs, including 138 groups (83.1%) with transcriptional evidence. A total of 2948 proteins are designated as MPs, and 5.6% of these were identified in this study. The high incidence of MPs in testis tissue indicates that this is a rich resource for MPs. Functional category analysis revealed that the biological processes that testis MPs are mainly involved in are sexual reproduction and spermatogenesis. Some of the MPs are potentially involved in tumorgenesis in other tissues. Therefore, this proteogenomics analysis of individual testis tissues provides convincing evidence of the discovery of MPs. All mass spectrometry data from this study have been deposited in the ProteomeXchange (data set identifier PXD002179).

Nuclear noncoding RNA surveillance: is the end in sight?

Nuclear noncoding RNA (ncRNA) surveillance pathways play key roles in shaping the steady-state transcriptomes of eukaryotic cells. Defective and unneeded ncRNAs are primarily degraded by exoribonucleases that rely on protein cofactors to identify these RNAs. Recent studies have begun to elucidate both the mechanisms by which these cofactors recognize aberrant RNAs and the features that mark RNAs for degradation. One crucial RNA determinant is the presence of an accessible end; in addition, the failure of aberrant RNAs to fold into compact structures and assemble with specific binding proteins probably also contributes to their recognition and subsequent degradation. To date, ncRNA surveillance has been most extensively studied in budding yeast. However, mammalian cells possess nucleases and cofactors that have no known yeast counterparts, indicating that RNA surveillance pathways may be more complex in metazoans. Importantly, there is evidence that the failure of ncRNA surveillance pathways contributes to human disease.

Non-coding Y RNAs as tethers and gates: Insights from bacteria.

Non-coding RNAs (ncRNAs) called Y RNAs are abundant components of both animal cells and a variety of bacteria. In all species examined, these ~100 nt RNAs are bound to the Ro 60 kDa (Ro60) autoantigen, a ring-shaped protein that also binds misfolded ncRNAs in some vertebrate nuclei. Although the function of Ro60 RNPs has been mysterious, we recently reported that a bacterial Y RNA tethers Ro60 to the 3' to 5' exoribonuclease polynucleotide phosphorylase (PNPase) to form RYPER (Ro60/Y RNA/PNPase Exoribonuclease RNP), a new RNA degradation machine. PNPase is a homotrimeric ring that degrades single-stranded RNA, and Y RNA-mediated tethering of Ro60 increases the effectiveness of PNPase in degrading structured RNAs. Single particle electron microscopy of RYPER suggests that RNA threads through the Ro60 ring into the PNPase cavity. Further studies indicate that Y RNAs may also act as gates to regulate entry of RNA substrates into the Ro60 channel. These findings reveal novel functions for Y RNAs and raise questions about how the bacterial findings relate to the roles of these ncRNAs in animal cells. Here we review the literature on Y RNAs, highlighting their close relationship with Ro60 proteins and the hypothesis that these ncRNAs function generally to tether Ro60 rings to diverse RNA-binding proteins.

[Serum sCD44v6 and sE-cadherin levels in patients with esophageal squamous cell carcinoma].

OBJECTIVE: To investigate the serum levels of sCD44v6 and sE-cadherin (sE-cad) in patients with esophageal squamous cell carcinoma. METHODS: The serum samples were collected from 65 cases of esophageal squamous cell carcinoma, 32 cases of erosive esophagitis and 35 healthy subjects. Serum sCD44v6 and sE-cad levels were measured by enzyme linked immunosorbent assay (ELISA). RESULTS: The mean levels of serum sCD44v6 and sE-cad in esophageal squamous cell carcinoma patients were significantly higher than those of erosive esophagitis patients and normal controls (both P<0.05). There was no significant difference in serum sCD44v6 and sE-cad levels between erosive esophagitis patients normal controls (P=0.566 and P=0.708, respectively). Serum sCD44v6 and sE-cad levels of esophageal cancer patients were not correlated with their clinicopathological features. Serum sCD44v6 level is not correlated with sE-cad level in squamous cell carcinoma patients(P=0.651). CONCLUSION: Serum sCD44v6 and sE-cad might be a potential marker for screening of esophageal squamous cell carcinoma.

Effect of circRNA_FOXO3 rs12196996 polymorphism and FOXO3 rs2232365 polymorphism on survival rate and severity of intensive care unit-acquired sepsis.

The expression of circRNA_FOXO3 was found to be positively associated with the expression of Forkhead Box O3 (FOXO3), which is targeted and regulated by miR-23a. Polymorphisms in rs12196996 and rs2232365 have been reported in various diseases. In this study, we recruited intensive care unit (ICU)-acquired sepsis patients and grouped them according to their genotypes of rs12196996 and rs2232365. Quantitative real-time PCR was performed to analyze the expression of circRNA_FOXO3, FOXO3 mRNA, and miR-23a. ELISA was carried out to evaluate the abundance of cytokines and luciferase assay was used to explore the inhibitory role of miR-23a on circRNA_FOXO3 and FOXO3. Accordingly, we found that rs12196996 GG and rs2232365 AA were significantly correlated with prolonged survival of ICU-acquired sepsis patients. Rs12196996 GG and rs2232365 AA were also correlated with increased level of miR-23a, IL-10 and decreased level of TNF, IL-2, IFN, IL-6 and IL-1ß in the peripheral blood cell samples of patients with ICU-acquired sepsis. The luciferase activity of wild-type (WT) circRNA_FOXO3 and FOXO3 were severely reduced by miR-23a. MiR-23a precursors could effectively suppress the expression of circRNA_FOXO3 and FOXO3 in the cells. Moreover, LPS-induced cell viability loss and dysregulation of cytokines were effectively restored by the knockdown of FOXO3 or circRNA_FOXO3 siRNA in the cells. This study revealed that the minor allele of rs12196996 polymorphism and rs2232365 polymorphism collaboratively contributed to the increased survival and suppressed severity of ICU-acquired sepsis.

Fe³âº-immobilized nanoparticle-modified capillary for capillary electrophoretic separation of phosphoproteins and non-phosphoproteins.

A fused-silica capillary modified with Fe³âº-immobilized magnetic nanoparticles (Fe³âº-IMAN) has been investigated for the capillary electrophoretic (CE) separation of phosphoproteins and non-phosphoproteins. The Fe³âº-IMAN capillary was achieved by covalently immobilising epoxy-based magnetic silica nanoparticles (160 nm) on the prederivatized 3-aminopropyl-trimethoxysilane (APTMS) fused-silica capillary (75 µm id), followed by disodium iminodiacetate and Fe³âº. The buildup process was examined by measuring the streaming potentials of the bare capillary, APTMS capillary, epoxy-based nanoparticle capillary and Fe³âº-IMAN capillary by varying the buffer pH. An inverted fluorescence microscope was used to determine the surface features of the Fe³âº-IMAN capillary derivatized with morin. Further experimental results confirmed that Fe³âº-IMAN bonded on the inner wall of the APTMS capillary could provide sufficient solute-bonded phase interactions to allow for the CE separation of phosphoproteins and non-phosphoproteins at concentration levels down to 50 µg/mL. The highest number of theoretical plates obtained was about 233,000/m, and the relative standard deviation (RSD) for migration times was <2.57% for eight consecutive runs, respectively. Additionally, the Fe³âº-IMAN modifing method was also applied to the analyses of bovine milk proteins. With simplicity, high resolving power, and high repeatability, the proposed method has shown great potential for phosphoproteomics applications.

Combination adjuvant chemotherapy with oxaliplatin, 5-fluorouracil and leucovorin after liver transplantation for hepatocellular carcinoma: a preliminary open-label study.

The purpose of this study was to evaluate the efficacy of postoperative adjuvant chemotherapy with FOLFOX regimen on the outcome after LT for HCC patients who did not meet the Milan criteria. Ninety-five consecutive HCC patients with liver cirrhosis undergoing LT were enrolled. Fifty-eight who did not meet the Milan criteria were randomized to open-label treatment with or without adjuvant chemotherapy after LT (n = 29/group). The FOLFOX chemotherapy protocol comprised 3-week cycles of oxaliplatin 100 mg/m(2) on day 1, leucovorin (calcium folinate, CF) 200 mg/m(2) on day 1 followed by 3-day, and 5-fluorouracil (5-FU) 2000 mg/m(2) as a 48-h continuous infusion, for up to six courses in the 1st year after transplantation. Median survival was extended by 4.57 months by combination chemotherapy. The 1- and 3-year survival rates were 89.7% and 79.3% with chemotherapy versus 69.0% and 62.1% without chemotherapy. The cumulative 1-year survival was significantly increased by chemotherapy (log-rank test, P = 0.043). The 6-month tumor-free survival rate was 24.1% higher with chemotherapy than without. The recurrence rate after LT was significantly different between the two groups at 6 months (P = 0.036), but not at 3 years (P = 0.102). The chemotherapy regimen was generally well tolerated. Post-LT adjuvant chemotherapy with oxaliplatin/5-FU/CF could not prevent tumor recurrence post-LT but may contribute to improve the survival of HCC patients who do not meet the Milan criteria. These results should be verified in a larger sample with a longer follow-up period.

The Efficacy of Memantine for the Treatment of Migraine: A Meta-Analysis of Randomized Controlled Studies.

INTRODUCTION: The efficacy of memantine for migraine remains controversial. We conduct a systematic review and meta-analysis to explore the influence of memantine versus placebo on treatment in migraine patients. METHODS: We search PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through February 2020 for randomized controlled trials assessing the effect of memantine versus placebo on treatment efficacy in migraine patients. This meta-analysis is performed using the random-effect model. RESULTS: Three randomized controlled trials are included in the meta-analysis. Overall, compared with control group in migraine patients, memantine treatment is associated with substantially reduced monthly attack frequency (mean difference [MD], -2.14; 95% confidence interval [CI], -2.83 to -1.46; P < 0.00001), number of migraine days (MD, -4.17; 95% CI, -6.40 to -1.93; P = 0.0003) and Migraine Disability Assessment (MD, -5.63; 95% CI, -6.46 to -4.79; P < 0.00001), but demonstrates no obvious influence on acute pain medications (MD, -1.23; 95% CI, -4.63 to 2.17; P = 0.48). CONCLUSIONS: Memantine treatment may benefit to the control of migraine.

Monitoring responses of vegetation phenology and productivity to extreme climatic conditions using remote sensing across different sub-regions of China.

Drought is a major natural disaster that significantly impacts the susceptibility and flexibility of the ecosystem by changing vegetation phenology and productivity. This study aimed to investigate the impact of extreme climatic variation on vegetation phenology and productivity over the four sub-regions of China from 2000 to 2017. Daily rain gauge precipitation and air temperature datasets were used to estimate the trends, and to compute the standardized precipitation-evapotranspiration index (SPEI). Remote sensing-based Enhanced Vegetation Index (EVI) data from a moderate resolution imaging spectroradiometer (MODIS) was used to characterize vegetation phenology. The results revealed that (1) air temperature had significant increasing trends (P < 0.05) in all sub-regions. Precipitation showed a non-significant increasing trend in Northwest China (NWC) and insignificant decreasing trends in North China (NC), Qinghai Tibet area (QTA), and South China (SC). (2) Integrated enhanced vegetation index (iEVI) and SPEI variations depicted that 2011 and 2016 were the extremely driest and wettest years during 2000-2017. (3) Rapid changes were observed in the vegetation phenology and productivity between 2011 and 2016. In 2011, changes in the vegetation phenology with the length of the growing season (ΔLGS) = was - 14 ± 36 days. In 2016, the overall net effect changed at the onset and end of the growing season with ΔLGS of 34 ± 71 days. The change in iEVI per SPEI increased rapidly with a changing rate of 0.16 from arid (NWC, and QTA) to semi-arid (NWC, QTA and NC) and declined with a rate of - 0.04 from semi-humid (QTA, NC, and SC) to humid (SC) region. A higher association was observed between iEVI and SPEI as compared to iEVI and precipitation. Our finding exposed that north China is more sensitive to climatic variation.

Optimizing biochar application to improve soil physical and hydraulic properties in saline-alkali soils.

Biochar application has been a promising approach to improve soil quality but their optimal amount in improving physical and hydraulic properties remains contradictory and inconclusive. The objective of this study was to examine and propose an optimal biochar application amount in saline alkali soil considering their impact on soil physical and hydraulic properties. A three-year field experiment was conducted in the saline-alkali soils under plastic film-mulched drip irrigation in Xinjiang, China. The studied physical and hydraulic properties included bulk density, soil porosity, saturated soil water content (θs), permanent wilting point (PWP), field capacity (FC), plant available water (PAW), spatial distribution of soil water content, planar soil water storage (PSWS), and soil evaporation. The treatments included biochar application amounts of 0 (CK), 10 (B10), 50 (B50), and 100 t ha-1 (B100) in 2018. Additional two treatments with 25 t ha-1 (B25) and 30 t ha-1 (B30) were added in 2019 and 2020, respectively. A four-parameter Gaussian function was fitted to the single-peak curves of the studied hydraulic properties vs. biochar application amounts to determine the most optimal biochar application amount. The results indicated that: (1) All of the biochar treatments significantly decreased bulk density and increased soil porosity over CK; (2) B10 and B25 treatments significantly increased θs, FC, PAW, PWP, and PSWS of root zones in the film-mulched zones over CK, but reverse results were observed in the B50 and B100 treatments; (3) Daily and cumulative soil evaporation were increased in no mulch zones of all biochar treatments over CK; (4) A dose of 21.9 t ha-1 was recommended as the most optimal biochar application amount for improving physical and hydraulic properties of saline-alkali soil. This research provided useful information on biochar application amounts for improving physical and hydraulic properties in saline-alkali soil.

Performance and relationship of four different agricultural drought indices for drought monitoring in China's mainland using remote sensing data.

Increasing frequency and intensity of extreme drought events have harmed the environment, ecosystem, and agricultural productivity. However, the characteristics of agricultural drought in China have not been well understood. The remote sensing (RS) based gridded monthly precipitation, soil moisture, land surface temperature (LST), and normalized difference vegetation index (NDVI) datasets over 1982-2018 were utilized to derive standardized precipitation index (SPI), standardized soil moisture index (SSI), multivariate standardized drought index (MSDI), and vegetation health index (VHI). The variation patterns and trends of SPI, SSI, and MSDI at the 1-, 3-, and 6-month timescales against monthly VHI anomaly were compared to identify the best agricultural drought index in China. The drought variations in the four sub-regions (northwest, north, Qinghai-Tibet area, and south area) were also investigated. The results showed that: (1) Temporal patterns of VHI anomaly were similar to relative soil moisture and slightly different from precipitation. The spatial patterns of MSDI matched with VHI the best than SPI and SSI. (2) All three indices showed positive correlations with VHI at the three timescales. The highest correlation coefficients (r) between MSDI and VHI ranged from 0.25 to 0.67, 0.22 to 0.78, 0.23 to 0.69, and 0.19 to 0.74 in northwest China, north China, Qinghai-Tibet Plateau, and south China, respectively. (3) The connections between monthly VHI and the three drought indices were weaker at the 1-month timescale (0.16 < r < 0.25) than the 3-month (0.39 < r < 0.78) and 6-month (0.26 < r < 0.68) timescales. (4) The VHI significantly increased in most of China except north China. Overall, MSDI showed better performance for monitoring agricultural drought in China's mainland.

Drought evolution indicated by meteorological and remote-sensing drought indices under different land cover types in China.

Remote sensing freely provides many processed image products such as moderate resolution imaging spectroradiometer (MODIS), and long-term data record (LTDR), for the investigation of drought evolution. Our objectives are to investigate drought evolution and spatiotemporal variations from 1982 to 2017 based on two remote-sensing indices, namely, the normalized difference vegetation index (NDVI) and the vegetation condition index (VCI), and a popular meteorological index-standardized precipitation index (SPI)-under four different land cover types, cropland, forestland, grassland, and desertland in China. The modified Mann-Kendall test was used to detect the significance of a trend. The Pearson correlation method was used to find the relationship between NDVI anomaly, VCI, precipitation, and SPI. The results revealed that (a) both mean monthly and yearly precipitation had a general land cover type rank of forestland > grassland ≈ cropland > desertland. (b) A positive correlation was found between drought indices (NDVI anomaly, VCI, SPI) and precipitation for different land cover types. The NDVI anomaly and VCI were well correlated with 3-month SPI for cropland and were well correlated with 6-month SPI for forestland. VCI performed better than NDVI anomaly when correlating with SPI. (c) The coefficient of determination (R2) was obtained for precipitation and VCI in the driest (2011) and wettest (2016) years. The R2 values for desert and grassland ranged from 0.70 to 0.90 and for cropland and forestland were lower (0.54-0.69). (d) Only precipitation, SPI, and VCI of cropland had significant increasing trends. The spatial distribution patterns of precipitation, NDVI, and VCI increased with the decreased elevation. The study revealed that desert and grassland had been regularly exposed to moderate or extreme droughts conditions and confirmed that desert and grassland are more sensitive to short-term drought.