Trithorax-group protein ATX5 mediates the glucose response via impacting the HY1-ABI4 signaling module

Key message

Trithorax-group Protein ARABIDOPSIS TRITHORAX5 modulates the glucose response.

Abstract

Glucose is an evolutionarily conserved modulator from unicellular microorganisms to multicellular animals and plants. Extensive studies have shown that the Trithorax-group proteins (TrxGs) play essential roles in different biological processes by affecting histone modifications and chromatin structures. However, whether TrxGs function in the glucose response and how they achieve the control of target genes in response to glucose signaling in plants remain unknown. Here, we show that the Trithorax-group Protein ARABIDOPSIS TRITHORAX5 (ATX5) affects the glucose response and signaling. atx5 loss-of-function mutants display glucose-oversensitive phenotypes compared to the wild-type (WT). Genome-wide RNA-sequencing analyses have revealed that ATX5 impacts the expression of a subset of glucose signaling responsive genes. Intriguingly, we have established that ATX5 directly controls the expression of HY1 by trimethylating H3 lysine 4 of the Arabidopsis Heme Oxygenase1 (HY1) locus. Glucose signaling causes the suppression of ATX5 activity and subsequently reduces the H3K4me3 levels at the HY1 locus, thereby leading to the increased expression of ABSCISIC ACID-INSENSITIVE4 (ABI4). This result suggests that an important ATX5-HY1-ABI4 regulatory module governs the glucose response. This idea is further supported by genetic evidence showing that an atx5 hy1-100 abi4 triple mutant showed a similar glucose-insensitive phenotype as compared to that of the abi4 single mutant. Our findings show that a novel ATX5-HY1-ABI4 module controls the glucose response in Arabidopsis thaliana.

     

Veratridine binding to a transmembrane helix of sodium channel Nav1.4 determined by solid-state NMR

The multi-step ligand action to a target protein is an important aspect when understanding mechanisms of ligand binding and discovering new drugs. However, structurally capturing such complex mechanisms is challenging. This is particularly true for interactions between large membrane proteins and small molecules. One such large membrane of interest is Na_v1.4, a eukaryotic voltage-gated sodium channel. Domain 4 segment 6 (D4S6) of Na_v1.4 is a transmembrane α-helical segment playing a key role in channel gating regulation, and is targeted by a neurotoxin, veratridine (VTD). VTD has been suggested to exhibit a two-step action to activate Na_v1.4. Here, we determine the NMR structure of a selectively ¹³C-labeled peptide corresponding to D4S6 and its VTD binding site in lipid bilayers determined by using magic-angle spinning solid-state NMR. By ¹³C NMR, we obtain NMR structural constraints as ¹³C chemical shifts and the ¹H-²H dipolar couplings between the peptide and deuterated lipids. The peptide backbone structure and its location with respect to the membrane are determined under the obtained NMR structural constraints aided by replica exchange molecular dynamics simulations with an implicit membrane/solvent system. Further, by measuring the ¹H-²H dipolar couplings to monitor the peptide-lipid interaction, we identify a VTD binding site on D4S6. When superimposed to a crystal structure of a bacterial sodium channel Na_vRh, the determined binding site is the only surface exposed to the protein exterior and localizes beside the second-step binding site reported in the past. Based on these results, we propose that VTD initially binds to these newly-determined residues on D4S6 from the membrane hydrophobic domain, which induces the first-step channel opening followed by the second-step blocking of channel inactivation of Na_v1.4. Our findings provide new detailed insights of the VTD action mechanism, which could be useful in designing new drugs targeting D4S6.     

六道沟流域2种典型灌木不同季节水分来源及利用效率

该试验以黄土高原风蚀水蚀区的典型代表六道沟流域为研究区,选取了2种典型灌木柠条(Caragana korshinskii)和沙柳(Salix psammophila)为研究对象,测定其茎秆水和不同层次土壤水分的δD值及叶片的δ~(13) C值,利用IsoSource模型分析2种植物对不同层次土壤水分的利用比例,并同步测定叶片水势、气孔导度、光合速率和蒸腾速率等生理生态因子,分析2种灌木在不同季节的水分来源及生理生态适应机制。结果表明:(1)柠条和沙柳的水分利用策略随季节波动,在不同季节对不同土层水分的利用比例存在差异。(2)旱季柠条和沙柳主要利用40~80cm土层的土壤水,利用比例分别为48.1%和49%。(3)雨季柠条主要利用表层0~10cm和浅层10~40cm的土壤水分,利用率约为57.5%;雨季沙柳主要利用浅层10~40cm的土壤水,利用比例达76%。(4)旱季柠条和沙柳的水分亏缺严重,其叶片水势、气孔导度、光合速率和蒸腾速率均小于雨季,而水分利用效率均大于雨季。研究发现,柠条和沙柳在旱季均主要利用深层土壤水分,雨季更倾向于利用浅层土壤水分;柠条和沙柳均能够通过降低气孔导度减小水分损失来获得较高的碳同化速率,维持较高的水分利用效率以适应干旱环境,均表现出较强的适应能力。     

Schinzel–Giedion syndrome: a novel case,review and revised diagnostic criteria

Schinzel–Giedion syndrome (SGS) is a rare autosomal dominant inheritance disorder. Heterozygous de novo mutations in the SETBP1 gene have been identified as the genetic cause of SGS. Here, we report a novel case with the syndrome with a novel insertion mutation in SETBP1. We also present a review of SGS cases, and first revise diagnostic criteria of SGS based on clinical findings and/or SETBP1 mutation worldwide. A revised diagnostic criteria and typing of SGS can be determined. Type I (complex and classic type) SGS patients present a development delay and typical facial features (prominent forehead, midface retraction, and short and upturned nose) associated with hydronephrosis or two of the characteristic skeletal anomalies (a sclerotic skull base, wide occipital synchondrosis, increased cortical density or thickness, and broad ribs). Type II (middle type) patients show development delay and the distinctive facial phenotype (midface retraction, short and upturned nose), lacking both hydronephrosis and typical skeletal abnormalities, with existence of SETBP1 mutation. Type III (simple type) patients with SETBP1 alteration show their major symptom is development delay, in which expressive language delay is the most striking feature. Central nervous system involvement with development delay in which expressive language delay is much more obviously affected is the most prominent feature of SGS. There is another indication that severity of phenotype of SGS may be inversely correlated with degree of SETBP1 alteration, besides gain-of-function or dominant-negative effects in SETBP1 alteration causing SGS.     

Lignin and extractives derived inhibitors in the 2,3-butanediol fermentation of mannose-rich prehydrolysates

Summary Mannose, the predominant sugar in southern pine water prehydrolysates, has been fermented to 2,3-butanediol by Klebsiella pneumoniae AU-1-d3. Lignin derivatives and extractives soluble in the water prehydrolysates, however, hindered the butanediol fermentation. Treatments with sequential lime-sulfuric acid or mixed bed ion resins facilitated the butanediol fermentation of the water prehydrolysates. Fermentation inhibitors derived from southern pine lignin and extractives were identified.     

庐山川续断属的新分类群

多年生草本,高2—3米。主根一条或数条,圆锥状,黄褐色。茎具纵棱6条,棱上疏生钩刺,近花序处较密。基生叶稀疏丛生有长柄,叶片阔倒卵形,长19—23厘米,宽19—26厘米,3深裂,中央裂片最大,阔倒卵形,长14—16厘米,宽8—10厘米,两侧裂片     

硬脊膜外腔注射辣椒素对大鼠一级传入C纤维的影响——组织化学与电镜观察

本文应用组织化学与电镜方法,观察了硬脊膜外腔注射辣椒素(CAP)对成年大鼠一级传入C纤维的影响。经CAP处理后第7天,大鼠脊髓后角Ⅰ～Ⅲ层内P物质(SP)免疫反应性明显减弱,抗氟化钠酸性磷酸酶(FRAP)活性消失或明显减弱,但亮氨酸脑啡肽(LEK)、神经降压素(NT)及5-羟色胺(5-HT)免疫反应性无明显变化。电镜观察发现,CAP处理后脊神经后根内部分无髓神经纤维被破坏,但有髓神经纤维无变化。在给药后48小时的脊髓胶状质(SG)内即可出现变性(DEG)终末,在第5、7、和10天,DEG终末增多,DEG程度加重。部分DEG终末属于Ⅰ型突触球的中央终末,但Ⅱ型突触球的中央终末无DEG征象。以上结果表明,成年大鼠硬脊膜外腔注射CAP亦可有效而特异地损毁一级传入C纤维。此动物模型的建立为选择性地研究C纤维与SG内其它结构之间的超微联系奠定了基础,并在进一步研究C纤维的功能方面具有一定的实用价值。