OPEN STOMATA 1 phosphorylates CYCLIC NUCLEOTIDE-GATED CHANNELs to trigger Ca2+ signaling for abscisic acid-induced stomatal closure in Arabidopsis.

Multiple cyclic nucleotide-gated channels (CNGCs) are abscisic acid (ABA)-activated Ca2+ channels in Arabidopsis (Arabidopsis thaliana) guard cells. In particular, CNGC5, CNGC6, CNGC9, and CNGC12 are essential for ABA-specific cytosolic Ca2+ signaling and stomatal movements. However, the mechanisms underlying ABA-mediated regulation of CNGCs and Ca2+ signaling are still unknown. In this study, we identified the Ca2+-independent protein kinase OPEN STOMATA 1 (OST1) as a CNGC activator in Arabidopsis. OST1-targeted phosphorylation sites were identified in CNGC5, CNGC6, CNGC9, and CNGC12. These CNGCs were strongly inhibited by Ser-to-Ala mutations and fully activated by Ser-to-Asp mutations at the OST1-targeted sites. The overexpression of individual inactive CNGCs (iCNGCs) under the UBIQUITIN10 promoter in wild-type Arabidopsis conferred a strong dominant-negative-like ABA-insensitive stomatal closure phenotype. In contrast, expressing active CNGCs (aCNGCs) under their respective native promoters in the cngc5-1 cngc6-2 cngc9-1 cngc12-1 quadruple mutant fully restored ABA-activated cytosolic Ca2+ oscillations and Ca2+ currents in guard cells, and rescued the ABA-insensitive stomatal movement mutant phenotypes. Thus, we uncovered that ABA elicits cytosolic Ca2+ signaling via an OST1-CNGC module, in which OST1 functions as a convergence point of the Ca2+-dependent and -independent pathways in Arabidopsis guard cells.

Multiple cyclic nucleotide-gated channels function as ABA-activated Ca2+ channels required for ABA-induced stomatal closure in Arabidopsis.

Abscisic acid (ABA)-activated inward Ca2+-permeable channels in the plasma membrane (PM) of guard cells are required for the initiation and regulation of ABA-specific cytosolic Ca2+ signaling and stomatal closure in plants. But the identities of the PM Ca2+ channels are still unknown. We hypothesized that the ABA-activated Ca2+ channels consist of multiple CYCLIC NUCLEOTIDE-GATED CHANNEL (CNGC) proteins from the CNGC family, which is known as a Ca2+-permeable channel family in Arabidopsis (Arabidopsis thaliana). In this research, we observed high expression of multiple CNGC genes in Arabidopsis guard cells, namely CNGC5, CNGC6, CNGC9, and CNGC12. The T-DNA insertional loss-of-function quadruple mutant cngc5-1 cngc6-2 cngc9-1 cngc12-1 (hereafter c5/6/9/12) showed a strong ABA-insensitive phenotype of stomatal closure. Further analysis revealed that ABA-activated Ca2+ channel currents were impaired, and ABA-specific cytosolic Ca2+ oscillation patterns were disrupted in c5/6/9/12 guard cells compared with in wild-type guard cells. All ABA-related phenotypes of the c5/6/9/12 mutant were successfully rescued by the expression of a single gene out of the four CNGCs under the respective native promoter. Thus, our findings reveal a type of ABA-activated PM Ca2+ channel comprising multiple CNGCs, which is essential for ABA-specific Ca2+ signaling of guard cells and ABA-induced stomatal closure in Arabidopsis.

Constitutive activation of a nuclear-localized calcium channel complex in Medicago truncatula.

Nuclear Ca2+ oscillations allow symbiosis signaling, facilitating plant recognition of beneficial microsymbionts, nitrogen-fixing rhizobia, and nutrient-capturing arbuscular mycorrhizal fungi. Two classes of channels, DMI1 and CNGC15, in a complex on the nuclear membrane, coordinate symbiotic Ca2+ oscillations. However, the mechanism of Ca2+ signature generation is unknown. Here, we demonstrate spontaneous activation of this channel complex, through gain-of-function mutations in DMI1, leading to spontaneous nuclear Ca2+ oscillations and spontaneous nodulation, in a CNGC15-dependent manner. The mutations destabilize a hydrogen-bond or salt-bridge network between two RCK domains, with the resultant structural changes, alongside DMI1 cation permeability, activating the channel complex. This channel complex was reconstituted in human HEK293T cell lines, with the resultant calcium influx enhanced by autoactivated DMI1 and CNGC15s. Our results demonstrate the mode of activation of this nuclear channel complex, show that DMI1 and CNGC15 are sufficient to create oscillatory Ca2+ signals, and provide insights into its native mode of induction.

A nomogram predicting the histologic activity of lupus nephritis from clinical parameters.

BACKGROUND: The 2021 clinical guidelines of the Kidney Disease: Improving Global Outcomes emphasize the importance of the histological activity index (AI) in the management of lupus nephritis (LN). Patients with LN and a high AI have poor renal outcomes and high rates of nephritic relapse. In this study we constructed prediction models for the AI in LN. METHODS: The study population comprised 337 patients diagnosed with LN using kidney biopsy. The participants were randomly divided into training and testing cohorts. They were further divided into high-activity (AI >2) and low-activity (AI ≤2) groups. This study developed two clinical prediction models using logistic regression and least absolute shrinkage and selection operator (LASSO) analyses with laboratory test results collected at the time of kidney biopsy. The performance of models was assessed using 5-fold cross-validation and validated in the testing cohort. A nomogram for individual assessment was constructed based on the preferable model. RESULTS: Multivariate analysis showed that higher mean arterial pressure, lower estimated glomerular filtration rate, lower complement 3 level, higher urinary erythrocytes count and anti-double-stranded DNA seropositivity were independent risk factors for high histologic activity in LN. Both models performed well in the testing cohort regarding the discriminatory ability to identify patients with an AI >2. The average area under the curve of 5-fold cross-validation was 0.855 in the logistic model and 0.896 in the LASSO model. A webtool based on the LASSO model was created for clinicians to enter baseline clinical parameters to produce a probability score of an AI >2. CONCLUSIONS: The established nomogram provides a quantitative auxiliary tool for distinguishing LN patients with a high AI and helps physicians make clinical decisions in their comprehensive assessment.

Transcriptomic Features of systemic lupus erythematosus Patients in Flare and Changes during Acute In-Hospital Treatment.

OBJECTIVES: Systemic lupus erythematosus (SLE) is a complex autoimmune disease with varying symptoms and multi-organ damage. Relapse-remission cycles often persist for many patients for years with the current treatment. Improved understanding of molecular changes caused by SLE flare and intensive treatment may result in more targeted therapies. METHODS: RNA-sequencing was performed on peripheral blood mononuclear cells (PBMCs) from 65 SLE patients in flare, collected both before (SLE1) and after (SLE2) in-hospital treatment, along with 15 healthy controls (HC). Differentially expressed genes (DEGs) were identified among the three groups. Enriched functions and key molecular signatures of the DEGs were analyzed and scored to elucidate the transcriptomic changes during treatment. RESULTS: Few upregulated genes in SLE1 vs HC were affected by treatment (SLE2 vs SLE1), mostly functional in interferon signalling (IFN), plasmablasts, and neutrophils. IFN and plasmablast signatures were repressed, but the neutrophil signature remained unchanged or enhanced by treatment. The IFN and neutrophil scores together stratified the SLE samples. IFN scores correlated well with leukopenia, while neutrophil scores reflected relative cell compositions but not cell counts. CONCLUSIONS: In-hospital treatment significantly relieved SLE symptoms with expression changes of a small subset of genes. Notably, IFN signature changes matched SLE flare and improvement, while enhanced neutrophil signature upon treatment suggested the involvement of low-density granulocytes (LDG) in disease development.

In situ deletions reveal regulatory components for expression of an intracellular immune receptor gene and its co-expressed genes in Arabidopsis.

Intracellular immune receptor nucleotide-binding leucine-rich repeats (NLRs) are highly regulated transcriptionally and post-transcriptionally for balanced plant defence and growth. NLR genes often exist in gene clusters and are usually co-expressed under various conditions. Despite of intensive studies of regulation of NLR proteins, cis-acting elements for NLR gene induction, repression or co-expression are largely unknown due to a larger than usual cis-region for their expression regulation. Here we used the CRISPR/Cas9 genome editing technology to generate a series of in situ deletions at the endogenous location of a NLR gene SNC1 residing in the RPP5 gene cluster. These deletions that made in the wild type and the SNC1 constitutive expressing autoimmune mutant bon1 revealed both positive and negative cis-acting elements for SNC1 expression. Two transcription factors that could bind to these elements were found to have an impact on the expression of SNC1. In addition, co-expression of two genes with SNC1 in the same cluster is found to be mostly dependent on the SNC1 function. Therefore, SNC1 expression is under complex local regulation involving multiple cis elements and SNC1 itself is a critical regulator of gene expression of other NLR genes in the same gene cluster.

Genome-wide assessment of genetic risk for systemic lupus erythematosus and disease severity.

Using three European and two Chinese genome-wide association studies (GWAS), we investigated the performance of genetic risk scores (GRSs) for predicting the susceptibility and severity of systemic lupus erythematosus (SLE), using renal disease as a proxy for severity. We used four GWASs to test the performance of GRS both cross validating within the European population and between European and Chinese populations. The performance of GRS in SLE risk prediction was evaluated by receiver operating characteristic (ROC) curves. We then analyzed the polygenic nature of SLE statistically. We also partitioned patients according to their age-of-onset and evaluated the predictability of GRS in disease severity in each age group. We found consistently that the best GRS in the prediction of SLE used SNPs associated at the level of P < 1e-05 in all GWAS data sets and that SNPs with P-values above 0.2 were inflated for SLE true positive signals. The GRS results in an area under the ROC curve ranging between 0.64 and 0.72, within European and between the European and Chinese populations. We further showed a significant positive correlation between a GRS and renal disease in two independent European GWAS (Pcohort1 = 2.44e-08; Pcohort2 = 0.00205) and a significant negative correlation with age of SLE onset (Pcohort1 = 1.76e-12; Pcohort2 = 0.00384). We found that the GRS performed better in the prediction of renal disease in the 'later onset' compared with the 'earlier onset' group. The GRS predicts SLE in both European and Chinese populations and correlates with poorer prognostic factors: young age-of-onset and lupus nephritis.

In situ deletions reveal regulatory components for expression of an intracellular immune receptor gene and its co-expressed genes in Arabidopsis.

Intracellular immune receptor nucleotide-binding leucine-rich repeats (NLRs) are highly regulated transcriptionally and post-transcriptionally for balanced plant defense and growth. NLR genes often exist in gene clusters and are usually co-expressed under various conditions. Despite intensive studies of the regulation of NLR proteins, cis-acting elements for NLR gene induction, repression or co-expression are largely unknown due to a larger than usual cis-region for their expression regulation. Here we used the CRISPR/Cas9 genome editing technology to generate a series of in situ deletions at the endogenous location of an NLR gene SNC1 residing in the RPP5 gene cluster. These deletions that made in the wild type and the SNC1 constitutive expressing autoimmune mutant bon1 revealed both positive and negative cis-acting elements for SNC1 expression. Two transcription factors that could bind to these elements were found to have an impact on the expression of SNC1. In addition, co-expression of two genes with SNC1 in the same cluster is found to be mostly dependent on the SNC1 function. Therefore, SNC1 expression is under complex local regulation involving multiple cis-elements and SNC1 itself is a critical regulator of gene expression of other NLR genes in the same gene cluster.

Effects of Long-Acting Somatostatin Analogues on Lipid Metabolism in Patients with Newly Diagnosed Acromegaly: A Retrospective Study of 120 Cases.

The short-term effects of long-acting somatostatin analogues (SSAs) on lipid profiles in patients with acromegaly are not well studied. We retrospectively analyzed the effects of SSAs on lipid profiles and associated cardiovascular risk factors in a cohort of 120 newly diagnosed acromegaly patients. In this study, 69 females and 51 males were included. These patients were treated with either octreotide LAR (OCT) or lanreotide SR (LAN) for 3 months. After SSAs treatment, both GH and IGF-1 significantly decreased (p<0.001). Triglyceride (TG), total to high-density lipoprotein cholesterol (HDL-C) ratio, and lipoprotein (a) [Lp(a)] levels were significantly decreased, while HDL-C levels were increased (p<0.05). The reduction of mean serum GH (GHm) was positively associated with the decrease of TG (r=0.305, p=0.001) and Lp(a) (r=0.257, p=0.005), as well as the increase of HDL-C (r=-0.355, p<0.001). The changes of lipid profiles were observed only in OCT group, but not in LAN group. In addition, systolic blood pressure (SBP) had significantly declined after SSAs treatment, with an average reduction of 4.4 mmHg (126.7±1.28 vs. 122.3±1.44 mmHg, p=0.003), while no change was observed regarding diastolic blood pressure (DBP) (p>0.05). Fasting insulin, fasting C-peptide, and HOMA-IR were significantly decreased after SSAs treatment. In conclusion, our current study revealed that short-term SSAs treatment improves lipid profiles and other cardiovascular risk factors in patients with acromegaly.

Shared genetic study gives insights into the shared and distinct pathogenic immunity components of IgA nephropathy and SLE.

An autoimmune component has been suggested to play a role in pathogenesis of IgA nephropathy (IgAN). And genetic studies have reported the shared susceptibility loci between IgAN and the prototype autoimmune disease systemic lupus erythematosus (SLE). This study was designed to systemically identify and annotate the shared susceptibility genes between IgAN and SLE. We first conducted an imputation-based genome-wide association analysis in 1180 IgAN cases and 899 controls, 1639 SLE cases and 2410 controls. Then we integrated blood expression quantitative trait loci (eQTL) databases and gene expression data to prioritize the potentially functional genes. The results showed that a total of 1928 SNPs mapping to 14 loci were identified to be shared genes between IgAN and SLE. Conditional analysis prioritized 18 independent SNPs, among which alleles of 4 SNPs in HLA and 7 SNPs in non-HLA loci were risk for SLE were protective alleles for IgAN. Most of the shared SNPs and their proxies (r2 ≥ 0.8 in Asians) (181/184, 98.37%) in non-HLA loci were located in non-coding regions. By analyzing two publicly independent blood-eQTL databases, four genes UBE2L3, FCGR2B, ANXA6, and BLK, which seemed to be restricted to PBMC or its subsets were prioritized. Among them only UBE2L3 showed consistent direction between SLE and IgAN, while the others showed opposite directions. Differential gene analysis showed that UBE2L3 was highly expressed in both SLE and IgAN, while FCGR2B and BLK showed marginal significance in SLE and IgAN, respectively. By exploring the pleiotropy of shared genes between IgAN and SLE, our results provide important clues for understanding the shared role of plasmablasts but the distinct role of B cells in pathogenesis of these two diseases.

Genome-wide association study on Northern Chinese identifies KLF2, DOT1L and STAB2 associated with systemic lupus erythematosus.

OBJECTIVES: To identify novel genetic loci associated with systemic lupus erythematosus (SLE) and to evaluate potential genetic differences between ethnic Chinese and European populations in SLE susceptibility. METHODS: A new genome-wide association study (GWAS) was conducted from Jining, North China, on 1506 individuals (512 SLE cases and 994 matched healthy controls). The association results were meta-analysed with existing data on Chinese populations from Hong Kong, Guangzhou and Central China, as well as GWAS results from four cohorts of European ancestry. A total of 26 774 individuals (9310 SLE cases and 17 464 controls) were included in this study. RESULTS: Meta-analysis on four Chinese cohorts identifies KLF2 as a novel locus associated with SLE [rs2362475; odds ratio (OR) = 0.85, P=2.00E-09]. KLF2 is likely an Asian-specific locus as no evidence of association was detected in the four European cohorts (OR = 0.98, P =0.58), with evidence of heterogeneity (P=0.0019) between the two ancestral groups. Meta-analyses of results from both Chinese and Europeans identify STAB2 (rs10082873; OR= 0.89, P=4.08E-08) and DOT1L (rs4807205; OR= 1.12, P=8.17E-09) as trans-ancestral association loci, surpassing the genome-wide significance. CONCLUSIONS: We identified three loci associated with SLE, with KLF2 a likely Chinese-specific locus, highlighting the importance of studying diverse populations in SLE genetics. We hypothesize that DOT1L and KLF2 are plausible SLE treatment targets, with inhibitors of DOT1L and inducers of KLF2 already available clinically.

The AWPM-19 Family Protein OsPM1 Mediates Abscisic Acid Influx and Drought Response in Rice.

Abscisic acid (ABA) regulates plant stress responses and development. However, how the ABA signal is transmitted in response to stresses remains largely unclear, especially in monocots. In this study, we found that rice (Oryza sativa) OsPM1 (PLASMA MEMBRANE PROTEIN1), encoded by a gene of AWPM-19 like family, mediates ABA influx through the plasma membrane. OsPM1 is predominantly expressed in vascular tissues, guard cells, and mature embryos. Phenotypic analysis of overexpression, RNA interference (RNAi), and knockout (KO) lines showed that OsPM1 is involved in drought responses and seed germination regulation. 3H-(±)ABA transport activity and fluorescence resonance energy transfer assays both demonstrated that OsPM1 facilitates ABA uptake into cells. The physiological isomer of ABA, (+)-ABA, is the preferred substrate of OsPM1. Higher ABA accumulation and faster stomatal closure in response to ABA treatment were observed in the overexpression lines compared with the wild-type control. Many ABA-responsive genes were upregulated more in the OsPM1-overexpression lines but less in the RNAi lines compared with wild-type plants. Further investigation revealed that OsPM1 expression is regulated by the AREB/ABF family transcription factor OsbZIP46. Our results thus revealed that OsPM1 is an ABA influx carrier that plays an important role in drought responses.

Effect of mangrove restoration on sediment properties and bacterial community.

Mangrove reconstruction is an efficient approach for mangrove conservation and restoration. The present study aimed to explore the effects of mangrove reconstruction on sediment properties and bacterial community. The results showed that mangrove restoration greatly promoted sediment fertility, whereas the improvements were more obvious induced by Kandelia obovata when compared to Avicennia marina. In all the samples, the dominant top5 bacterial group were Proteobacteria (48.31-54.52%), Planctomycetes (5.98-8.48%), Bacteroidetes (4.49-11.14%) and Acidobacteria (5.69-8.16%). As for the differences among the groups, the relative abundance of Chloroflexi was higher in the sediments of K. obovata, while Bacteroidetes was more abundant in A. marina group. Furthermore, the two bacterial genera (Rhodoplanes and Novosphingobium) were more dominant in the sediments of K. obovata, while the sediments of A. marina contained higher abundance of Vibrio and Marinobacterium. Besides, bacterial community was highly correlated with mangrove species and sediment property and nutrient status. The results of this study would provide a better understanding of the ecological benefits of mangroves and highlighted the information on biogeochemical processes driven by mangrove restoration and microorganisms.

HLA-IMPUTER: an easy to use web application for HLA imputation and association analysis using population-specific reference panels.

SUMMARY: HLA allele imputation from SNP genotypes has become increasingly useful, but its accuracy is heavily dependent on the reference panels used. HLA-IMPUTER implements HIBAG algorithm for HLA imputation with different population specific reference panels, including a new Han Chinese reference panel derived from 10 689 samples. We provide a convenient platform for researchers to impute HLA alleles and perform association analysis. AVAILABILITY AND IMPLEMENTATION: http://wyanglab.org: 3838/RefPanelWebsite/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

AtHKT1 drives adaptation of Arabidopsis thaliana to salinity by reducing floral sodium content.

Arabidopsis thaliana high-affinity potassium transporter 1 (AtHKT1) limits the root-to-shoot sodium transportation and is believed to be essential for salt tolerance in A. thaliana. Nevertheless, natural accessions with 'weak allele' of AtHKT1, e.g. Tsu-1, are mainly distributed in saline areas and are more tolerant to salinity. These findings challenge the role of AtHKT1 in salt tolerance and call into question the involvement of AtHKT1 in salinity adaptation in A. thaliana. Here, we report that AtHKT1 indeed drives natural variation in the salt tolerance of A. thaliana and the coastal AtHKT1, so-called weak allele, is actually hyper-functional in reducing flowers sodium content upon salt stress. Our data showed that AtHKT1 positively contributes to saline adaptation in a linear manner. Forward and reverse genetics analysis established that the single AtHKT1 locus is responsible for the variation in the salinity adaptation between Col-0 and Tsu-1. Reciprocal grafting experiments revealed that shoot AtHKT1 determines the salt tolerance of Tsu-1, whereas root AtHKT1 primarily drives the salt tolerance of Col-0. Furthermore, evidence indicated that Tsu-1 AtHKT1 is highly expressed in stems and is more effective compared to Col-0 AtHKT1 at limiting sodium flow to the flowers. Such efficient retrieval of sodium to the reproductive organ endows Tsu-1 with stronger fertility compared to Col-0 upon salt stress, thus improving Tsu-1 adaptation to a coastal environment. To conclude, our data not only confirm the role of AtHKT1 in saline adaptation, but also sheds light on our understanding of the salt tolerance mechanisms in plants.

Genetic studies on systemic lupus erythematosus in East Asia point to population differences in disease susceptibility.

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease with extreme clinical heterogeneity and significant differences between populations. East Asian populations are known to have higher prevalence and more severe clinical manifestations for SLE than Europeans. The difference could be the result of genetic and environmental factors, and the interactions between them. Thus, identifying genetic associations from diverse populations provides an opportunity to better understand the genetic architecture of this heterogeneous disease. It is also necessary to elucidate population differences and to apply the findings in future stratified treatment of the disease, with ethnicity likely a major factor to consider. Indeed, it has shown that there are significant differences between East Asians and European populations in several genetic loci for SLE. Genetic studies on SLE are very active in East Asian countries and there have been close collaborations among scientists in this region. Here, we document some work done in this region on SLE genetic research and discuss the aspect of population differences.

S-type Anion Channels SLAC1 and SLAH3 Function as Essential Negative Regulators of Inward K+ Channels and Stomatal Opening in Arabidopsis.

Drought stress induces stomatal closure and inhibits stomatal opening simultaneously. However, the underlying molecular mechanism is still largely unknown. Here we show that S-type anion channels SLAC1 and SLAH3 mainly inhibit inward K+ (K+in) channel KAT1 by protein-protein interaction, and consequently prevent stomatal opening in Arabidopsis. Voltage-clamp results demonstrated that SLAC1 inhibited KAT1 dramatically, but did not inhibit KAT2. SLAH3 inhibited KAT1 to a weaker degree relative to SLAC1. Both the N terminus and the C terminuses of SLAC1 inhibited KAT1, but the inhibition by the N terminus was stronger. The C terminus was essential for the inhibition of KAT1 by SLAC1. Furthermore, drought stress strongly up-regulated the expression of SLAC1 and SLAH3 in Arabidopsis guard cells, and the over-expression of wild type and truncated SLAC1 dramatically impaired K+in currents of guard cells and light-induced stomatal opening. Additionally, the inhibition of KAT1 by SLAC1 and KC1 only partially overlapped, suggesting that SLAC1 and KC1 inhibited K+in channels using different molecular mechanisms. Taken together, we discovered a novel regulatory mechanism for stomatal movement, in which singling pathways for stomatal closure and opening are directly coupled together by protein-protein interaction between SLAC1/SLAH3 and KAT1 in Arabidopsis.

Cyclic nucleotide-gated channel 18 is an essential Ca2+ channel in pollen tube tips for pollen tube guidance to ovules in Arabidopsis.

In flowering plants, pollen tubes are guided into ovules by multiple attractants from female gametophytes to release paired sperm cells for double fertilization. It has been well-established that Ca(2+) gradients in the pollen tube tips are essential for pollen tube guidance and that plasma membrane Ca(2+) channels in pollen tube tips are core components that regulate Ca(2+) gradients by mediating and regulating external Ca(2+) influx. Therefore, Ca(2+) channels are the core components for pollen tube guidance. However, there is still no genetic evidence for the identification of the putative Ca(2+) channels essential for pollen tube guidance. Here, we report that the point mutations R491Q or R578K in cyclic nucleotide-gated channel 18 (CNGC18) resulted in abnormal Ca(2+) gradients and strong pollen tube guidance defects by impairing the activation of CNGC18 in Arabidopsis. The pollen tube guidance defects of cngc18-17 (R491Q) and of the transfer DNA (T-DNA) insertion mutant cngc18-1 (+/-) were completely rescued by CNGC18. Furthermore, domain-swapping experiments showed that CNGC18's transmembrane domains are indispensable for pollen tube guidance. Additionally, we found that, among eight Ca(2+) channels (including six CNGCs and two glutamate receptor-like channels), CNGC18 was the only one essential for pollen tube guidance. Thus, CNGC18 is the long-sought essential Ca(2+) channel for pollen tube guidance in Arabidopsis.

The S-Type Anion Channel ZmSLAC1 Plays Essential Roles in Stomatal Closure by Mediating Nitrate Efflux in Maize.

Diverse stimuli induce stomatal closure by triggering the efflux of osmotic anions, which is mainly mediated by the main anion channel SLAC1 in plants, and the anion permeability and selectivity of SLAC1 channels from several plant species have been reported to be variable. However, the genetic identity as well as the anion permeability and selectivity of the main S-type anion channel ZmSLAC1 in maize are still unknown. In this study, we identified GRMZM2G106921 as the gene encoding ZmSLAC1 in maize, and the maize mutants zmslac1-1 and zmslac1-2 harboring a mutator (Mu) transposon in ZmSLAC1 exhibited strong insensitive phenotypes of stomatal closure in response to diverse stimuli. We further found that ZmSLAC1 functions as a nitrate-selective anion channel without obvious permeability to chloride, sulfate and malate, clearly different from SLAC1 channels of Arabidopsis thaliana, Brassica rapa ssp. chinensis and Solanum lycopersicum L. Further experimental data show that the expression of ZmSLAC1 successfully rescued the stomatal movement phenotypes of the Arabidopsis double mutant atslac1-3atslah3-2 by mainly restoring nitrate-carried anion channel currents of guard cells. Together, these findings demonstrate that ZmSLAC1 is involved in stomatal closure mainly by mediating the efflux of nitrate in maize.

Arctigenin Attenuates Ischemia/Reperfusion Induced Ventricular Arrhythmias by Decreasing Oxidative Stress in Rats.

BACKGROUND/AIMS: Arctigenin (ATG) has been shown to possess anti-inflammatory, immunemodulatory, anti-viral, anti-microbial, anti-carcinogenic, vasodilatory and anti-platelet aggregation properties. However, the protective role of ATG in prevention of arrhythmias induced by myocardial ischemia/reperfusion is unknown. The aim of this study was to investigate the anti-arrhythmia effect of ATG in an ischemia/reperfusion injured rat heart model and explore the related mechanisms. METHODS: Rats were randomly exposed to sham operation, myocardial ischemia/ reperfusion (MI/R) alone, ATG+ MI/R, pretreated with ATG in low (12.5 mg/kg/day), medium (50 mg/kg/day) and high dose (200 mg/kg/day), respectively. Ventricular arrhythmias were assessed. The activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and the level of malondialdehyde (MDA) in myocardial tissue were determined by chemical analysis. RESULTS: Compared to MI/R, rats pretreated with ATG in doses of 50 mg/kg/day and 200 mg/kg/day showed significantly reduced incidence and duration of ventricular fibrillation, ventricular tachycardia and ventricular ectopic beat (VEB), and decreased the arrhythmia score during the 30-min ischemia. Incidence and duration of ventricular tachycardia, infarction size and arrhythmia scores in these groups were significantly decreased during the 120-min reperfusion. No ventricular fibrillation occurred during the period of reperfusion. Rats pretreated with ATG in doses of 50 mg/kg/day and 200 mg/kg/ day markedly enhanced the activities of antioxidant enzymes SOD and GSH-Px, reduced the level of MDA. No differences were observed between the group pretreated with a low dose of ATG and the sham group. Administration of ATG significantly increased the expression of antioxidant stress protein Nrf2, Trx1 and Nox1. CONCLUSION: Our data suggested that ATG plays anti-arrhythmia role in ischemia/reperfusion injury, which is probably associated with attenuating oxidative stress by Nrf2 signaling pathway.