CEPs suppress auxin signaling but promote cytokinin signaling to inhibit root growth in Arabidopsis.

C-terminally encoded peptides (CEPs) are peptide hormones that function as mobile signals coordinating crucial developmental programs in plants. Previous studies have revealed that CEPs exert negative regulation on root development through interaction with CEP receptors (CEPRs), CEP DOWNSTREAMs (CEPDs), the cytokinin receptor ARABIDOPSIS HISTIDINE KINASE (AHKs) and the transcriptional repressor Auxin/Indole-3-Acetic Acid (AUX/IAA). However, the precise molecular mechanisms underlying CEPs-mediated regulation of root development via auxin and cytokinin signaling pathways still necessitate further detailed investigation. In this study, we examined prior research and elucidated the underlying molecular mechanisms. The results showed that both synthetic AtCEPs and overexpression of AtCEP5 markedly supressed primary root elongation and lateral root (LR) formation in Arabidopsis. Molecular biology and genetics elucidated how CEPs inhibit root growth by suppressing auxin signaling while promoting cytokinin signaling. In summary, this study elucidated the inhibitory effects of AtCEPs on Arabidopsis root growth and provided insights into their potential molecular mechanisms, thus enhancing our comprehension of CEP-mediated regulation of plant growth and development.

GH3-mediated auxin inactivation attenuates multiple stages of lateral root development.

Lateral root (LR) positioning and development rely on the dynamic interplay between auxin production, transport but also inactivation. Nonetheless, how the latter affects LR organogenesis remains largely uninvestigated. Here, we systematically analyze the impact of the major auxin inactivation pathway defined by GRETCHEN HAGEN3-type (GH3) auxin conjugating enzymes and DIOXYGENASE FOR AUXIN OXIDATION1 (DAO1) in all stages of LR development using reporters, genetics and inhibitors in Arabidopsis thaliana. Our data demonstrate that the gh3.1/2/3/4/5/6 hextuple (gh3hex) mutants display a higher LR density due to increased LR initiation and faster LR developmental progression, acting epistatically over dao1-1. Grafting and local inhibitor applications reveal that root and shoot GH3 activities control LR formation. The faster LR development in gh3hex is associated with GH3 expression domains in and around developing LRs. The increase in LR initiation is associated with accelerated auxin response oscillations coinciding with increases in apical meristem size and LR cap cell death rates. Our research reveals how GH3-mediated auxin inactivation attenuates LR development. Local GH3 expression in LR primordia attenuates development and emergence, whereas GH3 effects on pre-initiation stages are indirect, by modulating meristem activities that in turn coordinate root growth with LR spacing.

Diagnostic and prognostic significance of miR-451a in patients with atherosclerosis.

OBJECTIVES: Atherosclerosis (AS) is a chronic inflammatory vascular disease. This study aimed to detect the expression level of miR-451a and investigate the diagnostic and prognostic values of miR-451a for AS patients. METHODS: The relative expression of miR-451a was assessed by qRT-PCR. Comparison of groups was analyzed with the t-test and chi-squared test. Pearson analysis was used to validate the correlation of miR-451 with CRP and CIMT. The receiver operating characteristic (ROC) curves, K-M analysis, and Cox regression analysis were conducted to explore the roles of miR-451a in diagnosing AS patients and predicting outcomes of AS patients. RESULTS: The expression of miR-451a was significantly decreased in the serum of AS patients. The results of Pearson analysis showed the expression of miR-451a was negatively correlated with CRP and CIMT. The data of ROC proposed miR-451a could differentiate AS patients from healthy individuals with high sensitivity and specificity. K-M analysis and Cox regression showed miR-451a might be an independent biomarker of suffering cardiovascular endpoint diseases in AS patients. The expression of miR-451a was obviously inhibited in AS patients with cardiovascular endpoint events. CONCLUSION: Deregulation of miR-451a might be associated with the development of AS. MiR-451a might be used as a promising diagnostic and prognostic biomarker for clinical treatment of AS patients.

Periodic root branching is influenced by light through an HY1-HY5-auxin pathway.

The spacing of lateral roots (LRs) along the main root in plants is driven by an oscillatory signal, often referred to as the "root clock" that represents a pre-patterning mechanism that can be influenced by environmental signals. Light is an important environmental factor that has been previously reported to be capable of modulating the root clock, although the effect of light signaling on the LR pre-patterning has not yet been fully investigated. In this study, we reveal that light can activate the transcription of a photomorphogenic gene HY1 to maintain high frequency and amplitude of the oscillation signal, leading to the repetitive formation of pre-branch sites. By grafting and tissue-specific complementation experiments, we demonstrated that HY1 generated in the shoot or locally in xylem pole pericycle cells was sufficient to regulate LR branching. We further found that HY1 can induce the expression of HY5 and its homolog HYH, and act as a signalosome to modulate the intracellular localization and expression of auxin transporters, in turn promoting auxin accumulation in the oscillation zone to stimulate LR branching. These fundamental mechanistic insights improve our understanding of the molecular basis of light-controlled LR formation and provide a genetic interconnection between shoot- and root-derived signals in regulating periodic LR branching.

Influence of astragaloside IV on pharmacokinetics of triptolide in rats and its potential mechanism.

Context: It is common to combine two or more drugs in clinics in China. Triptolide (TP) has been used primarily for the treatment of inflammatory and autoimmune diseases. Astragaloside IV (AS-IV) has been applied with many other drugs, due to its various pharmacological effects. AS-IV and TP can be used together for the treatment of diseases in clinics in China.Objective: This study investigates the effects of astragaloside IV (AS-IV) on the pharmacokinetics of TP in rats and its potential mechanism.Materials and methods: The pharmacokinetics of orally administered triptolide (2 mg/kg) with or without AS-IV pre-treatment (100 mg/kg/day for 7 d) were investigated. Additionally, the effects of AS-IV on the transport of triptolide were investigated using the Caco-2 cell transwell model.Results: The results indicated that when the rats were pre-treated with AS-IV, the Cmax of triptolide decreased from 418.78 ± 29.36 to 351.31 ± 38.88 ng/mL, and the AUC0-t decreased from 358.83 ± 19.56 to 252.23 ± 15.75 µg/h/L. The Caco-2 cell transwell experiments indicated that AS-IV could increase the efflux ratio of TP from 2.37 to 2.91 through inducing the activity of P-gp.Discussion and conclusions: In conclusion, AS-IV could decrease the system exposure of triptolide when they are co-administered, and it might work through decreasing the absorption of triptolide by inducing the activity of P-gp.

Abscisic acid-triggered guard cell l-cysteine desulfhydrase function and in situ hydrogen sulfide production contributes to heme oxygenase-modulated stomatal closure.

Recent studies have demonstrated that hydrogen sulfide (H2 S) produced through the activity of l-cysteine desulfhydrase (DES1) is an important gaseous signaling molecule in plants that could participate in abscisic acid (ABA)-induced stomatal closure. However, the coupling of the DES1/H2 S signaling pathways to guard cell movement has not been thoroughly elucidated. The results presented here provide genetic evidence for a physiologically relevant signaling pathway that governs guard cell in situ DES1/H2 S function in stomatal closure. We discovered that ABA-activated DES1 produces H2 S in guard cells. The impaired guard cell ABA phenotype of the des1 mutant can be fully complemented when DES1/H2 S function has been specifically rescued in guard cells and epidermal cells, but not mesophyll cells. This research further characterized DES1/H2 S function in the regulation of LONG HYPOCOTYL1 (HY1, a member of the heme oxygenase family) signaling. ABA-induced DES1 expression and H2 S production are hyper-activated in the hy1 mutant, both of which can be fully abolished by the addition of H2 S scavenger. Impaired guard cell ABA phenotype of des1/hy1 can be restored by H2 S donors. Taken together, this research indicated that guard cell in situ DES1 function is involved in ABA-induced stomatal closure, which also acts as a pivotal hub in regulating HY1 signaling.

Methyl-coenzyme M reductase-dependent endogenous methane enhances plant tolerance against abiotic stress and alters ABA sensitivity in Arabidopsis thaliana.

KEY MESSAGE: Our study firstly elaborated the underlying mechanism of endogenous CH4-induced abiotic tolerance, along with an alteration of ABA sensitivity by mimicking the endogenous CH4 production in MtMCR transgenic Arabidopsis. Endogenous methane (CH4) production and/or emission have been ubiquitously observed in stressed plants. However, their physiological roles remain unclear. Here, the methyl-coenzyme M reductase gene from Methanobacterium thermoautotrophicum (MtMCR), encoding the enzyme of methanogenesis, was expressed in Arabidopsis thaliana, to mimic the production of endogenous CH4. In response to salinity and osmotic stress, MtMCR expression was up-regulated in transgenic plants, resulting in significant increase of endogenous CH4 levels. Similar results were observed in abscisic acid (ABA) treatment. The functions of endogenous CH4 were characterized by the changes in plant phenotypes related to stress and ABA sensitivity during the germination and post-germination periods. When challenged with osmotic stress, a reduction in water loss and stomatal closure, were observed. Redox homeostasis was reestablished during osmotic and salinity stress, and ion imbalance was also restored in salinity conditions. The expression of several stress/ABA-responsive genes was up-regulated, and ABA sensitivity, in particularly, was significantly altered in the MtMCR transgenic plants. Together, our genetic study for the first time elaborated the possible mechanism of endogenous CH4-enhanced salinity and osmotic tolerance, along with an alteration of ABA sensitivity. These findings thus provided novel cues for understanding the possible roles of endogenous CH4 in plants.

Association of serum nesfatin-1 concentrations with atrial fibrillation.

Nesfatin-1, a newly discovered adipokine, inhibits inflammatory response. Inflammation is involved in the mechanism of atrial fibrillation (AF). We aim to determine the association between serum nesfatin-1 concentrations and AF. A population of 200 patients with AF and 108 patients without AF were enrolled in this study. These patients were divided into three subgroups of paroxysmal AF, persistent AF, and permanent AF. Serum nesfatin-1 concentrations were lower in AF patients than in controls. Logistic regression analysis showed that serum nesfatin-1 concentrations were inversely associated with AF. Serum nesfatin-1 concentrations in permanent AF patients decreased compared with those in persistent and paroxysmal AF groups. In addition, persistent AF patients showed reduced serum nesfatin-1 concentrations compared with paroxysmal AF subjects. Serum nesfatin-1 concentrations were negatively correlated with left atrial diameter. In conclusion, serum nesfatin-1 concentrations were inversely correlated with AF development.

Hydrogen Gas Is Involved in Auxin-Induced Lateral Root Formation by Modulating Nitric Oxide Synthesis.

Metabolism of molecular hydrogen (H2) in bacteria and algae has been widely studied, and it has attracted increasing attention in the context of animals and plants. However, the role of endogenous H2 in lateral root (LR) formation is still unclear. Here, our results showed that H2-induced lateral root formation is a universal event. Naphthalene-1-acetic acid (NAA; the auxin analog) was able to trigger endogenous H2 production in tomato seedlings, and a contrasting response was observed in the presence of N-1-naphthyphthalamic acid (NPA), an auxin transport inhibitor. NPA-triggered the inhibition of H2 production and thereafter lateral root development was rescued by exogenously applied H2. Detection of endogenous nitric oxide (NO) by the specific probe 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA) and electron paramagnetic resonance (EPR) analyses revealed that the NO level was increased in both NAA- and H2-treated tomato seedlings. Furthermore, NO production and thereafter LR formation induced by auxin and H2 were prevented by 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO; a specific scavenger of NO) and the inhibitor of nitrate reductase (NR; an important NO synthetic enzyme). Molecular evidence confirmed that some representative NO-targeted cell cycle regulatory genes were also induced by H2, but was impaired by the removal of endogenous NO. Genetic evidence suggested that in the presence of H2, Arabidopsis mutants nia2 (in particular) and nia1 (two nitrate reductases (NR)-defective mutants) exhibited defects in lateral root length. Together, these results demonstrated that auxin-induced H2 production was associated with lateral root formation, at least partially via a NR-dependent NO synthesis.

Methane protects against polyethylene glycol-induced osmotic stress in maize by improving sugar and ascorbic acid metabolism.

Although aerobic methane (CH4) release from plants leads to an intense scientific and public controversy in the recent years, the potential functions of endogenous CH4 production in plants are still largely unknown. Here, we reported that polyethylene glycol (PEG)-induced osmotic stress significantly increased CH4 production and soluble sugar contents in maize (Zea mays L.) root tissues. These enhancements were more pronounced in the drought stress-tolerant cultivar Zhengdan 958 (ZD958) than in the drought stress-sensitive cultivar Zhongjiangyu No.1 (ZJY1). Exogenously applied 0.65 mM CH4 not only increased endogenous CH4 production, but also decreased the contents of thiobarbituric acid reactive substances. PEG-induced water deficit symptoms, such as decreased biomass and relative water contents in both root and shoot tissues, were also alleviated. These beneficial responses paralleled the increases in the contents of soluble sugar and the reduced ascorbic acid (AsA), and the ratio of AsA/dehydroascorbate (DHA). Further comparison of transcript profiles of some key enzymes in sugar and AsA metabolism suggested that CH4 might participate in sugar signaling, which in turn increased AsA production and recycling. Together, these results suggested that CH4 might function as a gaseous molecule that enhances osmotic stress tolerance in maize by modulating sugar and AsA metabolism.

Linking hydrogen-mediated boron toxicity tolerance with improvement of root elongation, water status and reactive oxygen species balance: a case study for rice.

BACKGROUND AND AIMS: Boron is essential for plant growth but hazardous when present in excess. As the antioxidant properties of hydrogen gas (H2) were recently described in plants, oxidative stress induced by excess boron was investigated along with other biological responses during rice (Oryza sativa) seed germination to study the beneficial role of H2 METHODS: Rice seeds were pretreated with exogenous H2 Using physiological, pharmacological and molecular approaches, the production of endogenous H2, growth status, reactive oxygen species (ROS) balance and relative gene expression in rice were measured under boron stress to investigate mechanisms of H2-mediated boron toxicity tolerance. KEY RESULTS: In our test, boron-inhibited seed germination and seedling growth, and endogenous H2 production, were obviously blocked by exogenously applying H2 The re-establishment of ROS balance was confirmed by reduced lipid peroxidation and ROS accumulation. Meanwhile, activities of catalase (CAT) and peroxidase (POX) were increased. Suppression of pectin methylesterase (PME) activity and downregulation of PME transcripts by H2 were consistent with the alleviation of root growth inhibition caused by boron. Water status was improved as well. This result was confirmed by the upregulation of genes encoding specific aquaporins (AQPs), the maintenance of low osmotic potential and high content of soluble sugar. Increased transcription of representative AQP genes (PIP2;7 in particular) and BOR2 along with decreased BOR1 mRNA may contribute to lowering boron accumulation. CONCLUSIONS: Hydrogen provides boron toxicity tolerance mainly by improving root elongation, water status and ROS balance.

Ectopic over-expression of BoHO1, a cabbage heme oxygenase gene, improved salt tolerance in Arabidopsis: A case study on proteomic analysis.

Plant heme oxygenase (HO) catalyzes the oxygenation of heme to biliverdin, carbon monoxide, and free iron, and is regarded as a stress-responsive protein. Here, a cabbage HO1 gene (named as BoHO1) was isolated and characterized. BoHO1 shares a high degree homology with Arabidopsis AtHO1, and could locate in Arabidopsis chloroplast. BoHO1 mRNA was ubiquitously expressed in cabbage tissues, and was responsive to several stimuli and chemicals. Genetic evidence illustrated that over-expression of BoHO1 in transgenic Arabidopsis plants (35S:BoHO1-1 and 35S:BoHO1-2) significantly alleviated salinity stress-inhibited seedling growth, which were accompanied with the re-establishment of reactive oxygen species and ion homeostasis. Comparative proteomic analysis was subsequently performed. Results revealed that protein abundance related to light reactions was greatly suppressed by NaCl stress in wild-type, whereas was partially recovered in 35S:BoHO1-1. Salinity stress also strongly activated stress-related metabolic processes in wild-type, i.e. carbon and energy metabolism, ammonium detoxification, and protein turnover, and these induced tendencies were more intensive in 35S:BoHO1-1. Particularly, proteins related to glutathione metabolism and ion homeostasis were specifically enriched in NaCl-stressed 35S:BoHO1-1. On the basis of above results, we propose that BoHO1 could activate multiple stress-responsive pathways to help Arabidopsis regain cellular homeostasis, thus presenting enhanced adaptation to salinity stress.

Arabidopsis HY1-Modulated Stomatal Movement: An Integrative Hub Is Functionally Associated with ABI4 in Dehydration-Induced ABA Responsiveness.

Heme oxygenase (HO; EC 1.14.99.3) has recently been proposed as a novel component in mediating wide ranges of the plant adaptive signaling processes. However, the physiological significance and molecular basis underlying Arabidopsis (Arabidopsis thaliana) HO1 (HY1) functioning in drought tolerance remained unclear. Here, we report that mutation of HY1 promoted, but overexpression of this gene impaired, Arabidopsis drought tolerance. This was attributed to the abscisic acid (ABA)-hypersensitive or -hyposensitive phenotypes, with the regulation of stomatal closure in particular. However, comparative transcriptomic profile analysis showed that the induction of numerous ABA/stress-dependent genes in dehydrated wild-type plants was differentially impaired in the hy1 mutant. In agreement, ABA-induced ABSCISIC ACID-INSENSITIVE4 (ABI4) transcript accumulation was strengthened in the hy1 mutant. Genetic analysis further identified that the hy1-associated ABA hypersensitivity and drought tolerance were arrested in the abi4 background. Moreover, the promotion of ABA-triggered up-regulation of RbohD abundance and reactive oxygen species (ROS) levels in the hy1 mutant was almost fully blocked by the mutation of ABI4, suggesting that the HY1-ABI4 signaling in the wild type involved in stomatal closure was dependent on the RbohD-derived ROS production. However, hy1-promoted stomatal closure was not affected by a nitric oxide scavenger. Correspondingly, ABA-insensitive behaviors in rbohD stomata were not affected by either the mutation of HY1 or its ectopic expression in the rbohD background, both of which responded significantly to exogenous ROS. These data indicate that HY1 functioned negatively and acted upstream of ABI4 in drought signaling, which was casually dependent on the RbohD-derived ROS in the regulation of stomatal closure.

Heme-heme oxygenase 1 system is involved in ammonium tolerance by regulating antioxidant defence in Oryza sativa.

Despite substantial evidence showing the ammonium-altered redox homeostasis in plants, the involvement and molecular mechanism of heme-heme oxygenase 1 (heme-HO1), a novel antioxidant system, in the regulation of ammonium tolerance remain elusive. To fill in these gaps, the biological function of rice HO1 (OsSE5) was investigated. Results showed that NH4 Cl up-regulated rice OsSE5 expression. Oxidative stress and subsequent growth inhibition induced by excess NH4 Cl was partly mitigated by pretreatment with carbon monoxide (CO, a by-product of HO1 activity) or intensified by zinc protoporphyrin (ZnPP, a potent inhibitor of HO1 activity). Pretreatment with HO1 inducer hemin, not only up-regulated OsSE5 expression and HO activity, but also rescued the down-regulation of antioxidant transcripts, total and related isozymatic activities, thus significantly counteracting the excess NH4 Cl-triggered reactive oxygen species overproduction, lipid peroxidation and growth inhibition. OsSE5 RNAi transgenic rice plants revealed NH4 Cl-hypersensitive phenotype with impaired antioxidant defence, both of which could be rescued by CO but not hemin. Transgenic Arabidopsis plants over-expressing OsSE5 also exhibited enhanced tolerance to NH4 Cl, which might be attributed to the up-regulation of several antioxidant transcripts. Altogether, these results illustrated the involvement of heme-HO1 system in ammonium tolerance by enhancing antioxidant defence, which may improve plant tolerance to excess ammonium fertilizer.

Hydrogen-rich water-alleviated ultraviolet-B-triggered oxidative damage is partially associated with the manipulation of the metabolism of (iso)flavonoids and antioxidant defence in Medicago sativa.

External administration of hydrogen gas (H2) benefits plants from multiple environmental stimuli. However, the physiological significance and molecular mechanism of H2 in ultraviolet-B (UVB) irradiation are largely unexplored. Here, the biological function of H2 in the regulation of plant UVB-tolerance was investigated by using hydrogen-rich water (HRW). Results showed that the exposure of alfalfa seedlings to UVB irradiation increased endogenous H2 production. Pretreatment with HRW mimicked the UVB-induced endogenous H2 production. Corresponding UVB-triggered toxic symptoms, in terms of lipid peroxidation and overproduction of reactive oxygen species (ROS), as well as the subsequent growth inhibition, were markedly mitigated. Metabolic profiling analysis by using ultra performance liquid chromatography-mass spectrometric (UPLC-MS), identified 40 (iso)flavonoids in UVB-treated alfalfa plants, with 22 kinds was increased by HRW. These changes resulted in the alternation of (iso)flavonoids profile, with the effective promotion of isoflavone and flavanone subfamilies in particular. These compounds included afromosin, afromosin 7-O-ß-D-glucoside-malonate, daidzein, formononetin 7-O-ß-D-glucoside-6''-O-malonate, garbanzol, matteucin and naringenin. In vitro tests further showed that the HRW-modulated (iso)flavonoids profile upon UVB stress possessed advanced ROS-quenching and antioxidant capacities under our experimental conditions. Meanwhile, UVB-triggered upregulation in the transcription levels of (iso)flavonoids biosynthetic-related genes were substantially strengthened by HRW. The activities and related transcripts of representative antioxidant enzymes were also induced. Taken together, our findings indicate that HRW confers tolerance to UVB-induced oxidative damage partially by the manipulation of (iso)flavonoids metabolism and antioxidant defence in Medicago sativa L.