Galium procurrens,a new diploid relic species of theG. sylvaticum-group from the Balkan Peninsula

Galium procurrens is described as a new diploid relic species from Montenegro/N. Albania and SW. Bulgaria. It is related to the tetraploidG. laevigatum and other diploid and polyploid taxa of theG. sylvaticum-group inhabiting European deciduous forests.     

塔里木河下游河水漫溢后胡杨幼苗分布格局初探

采用最近邻体法,将Clark-Evans指数作为度量胡杨幼苗分布格局的指标,并用标准正态分布检验实际CE指数值偏离1的显著性,分析塔里木河下游河水漫溢后胡杨幼苗的分布格局。结果表明:(1)在3m×3m的样方尺度上,河水漫溢后0～1年和1～2年的胡杨幼苗呈聚集分布,漫溢后2～3年的胡杨幼苗呈均匀分布,漫溢后4～5年和5～7年的胡杨幼苗呈随机分布。(2)在3m×3m的样方尺度上,随着胡杨幼苗年龄的增长,胡杨幼苗的空间分布格局由聚集分布转变为均匀分布,最终呈现为随机分布的格局。(3)在2m×2m至10m×10m的样方尺度上,漫溢后5～7年的胡杨幼苗空间分布格局均表现为随机分布。(4)标准正态分布检验结果显示,各个尺度上胡杨幼苗的CE值与理论值1之间的偏离均不显著,说明随着尺度的增大,胡杨幼苗的空间分布格局并没有发生显著变化,始终呈现出随机分布的格局。     

Nitrogen deficiency system is helpful in characterizing regulation mechanisms of ectopic triacylglycerol accumulation in Arabidopsis seedlings

Triacylglycerol (TAG) is the major storage component accumulated in seed. However the regulatory mechanism of TAG synthesis and accumulation in non-seed tissues remains unknown. Recently, we found that nitrogen (N) deficiency (0.1mM N) caused an inducement of TAG biosynthesis in Arabidopsis seedlings. ABSCISIC ACID INSENSITIVE 4 (ABI4) was essential for the activation of Acyl-CoA:diacylglycerol acyltransferase1(DGAT1) expression during N deficiency in Arabidopsis seedlings. In this addendum, we further discussed the approaches to provide a net increase in total oil production in higher plants by using the low N platform. First, the N-deficient seedlings can be used to determine the key factors that regulate the ectopic expression of key genes in TAG metabolism. Second, the research on the relationship between TAG homeostasis and cell division will be helpful to find the key factors that specifically regulate TAG accumulation under the nutrient-limited condition.     

The PDZ-GEF Gef26 regulates synapse development and function via FasII and Rap1 at the Drosophila neuromuscular junction

Guanine nucleotide exchange factors (GEFs) are essential for small G proteins to activate their downstream signaling pathways, which are involved in morphogenesis, cell adhesion, and migration. Mutants of Gef26, a PDZ-GEF (PDZ domain-containing guanine nucleotide exchange factor) in Drosophila, exhibit strong defects in wings, eyes, and the reproductive and nervous systems. However, the precise roles of Gef26 in development remain unclear. In the present study, we analyzed the role of Gef26 in synaptic development and function. We identified significant decreases in bouton number and branch length at larval neuromuscular junctions (NMJs) in Gef26 mutants, and these defects were fully rescued by restoring Gef26 expression, indicating that Gef26 plays an important role in NMJ morphogenesis. In addition to the observed defects in NMJ morphology, electrophysiological analyses revealed functional defects at NMJs, and locomotor deficiency appeared in Gef26 mutant larvae. Furthermore, Gef26 regulated NMJ morphogenesis by regulating the level of synaptic Fasciclin II (FasII), a well-studied cell adhesion molecule that functions in NMJ development and remodeling. Finally, our data demonstrate that Gef26-specific small G protein Rap1 worked downstream of Gef26 to regulate the level of FasII at NMJs, possibly through a βPS integrin-mediated signaling pathway. Taken together, our findings define a novel role of Gef26 in regulating NMJ development and function.     

Transforming Growth Factor-β (TGF-β) Expression Is Increased in the Subsynovial Connective Tissue in a Rabbit Model of Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) is an idiopathic disease that results from increased fibrosis of the subsynovial connective tissue (SSCT). A recent study found overexpression of both transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) in the SSCT of CTS patients. This study investigated TGF-β and CTGF expression in a rabbit model of CTS, in which SSCT fibrosis is induced by a surgical injury. Levels of TGF-β1 and CTGF at 6, 12, 24 weeks after injury were determined by immunohistochemistry A significant increase in TGF-β1 and a concomitant significant increase in CTGF were found at 6 weeks, in addition to higher cell density compared to normal (all p<0.05), Interestingly, CTGF expression was reduced at 12 and 24 weeks, suggesting that an initial insult results in a time limited response. We conclude that this rabbit model mimics the fibrosis found in human CTS, and may be useful to study pathogenetic mechanisms of CTS in vivo.     

Molecular mechanism of ERK dephosphorylation by striatal‐enriched protein tyrosine phosphatase

Striatal‐enriched tyrosine phosphatase (STEP) is an important regulator of neuronal synaptic plasticity, and its abnormal level or activity contributes to cognitive disorders. One crucial downstream effector and direct substrate of STEP is extracellular signal‐regulated protein kinase (ERK), which has important functions in spine stabilisation and action potential transmission. The inhibition of STEP activity toward phospho‐ERK has the potential to treat neuronal diseases, but the detailed mechanism underlying the dephosphorylation of phospho‐ERK by STEP is not known. Therefore, we examined STEP activity toward para‐nitrophenyl phosphate, phospho‐tyrosine‐containing peptides, and the full‐length phospho‐ERK protein using STEP mutants with different structural features. STEP was found to be a highly efficient ERK tyrosine phosphatase that required both its N‐terminal regulatory region and key residues in its active site. Specifically, both kinase interaction motif (KIM) and kinase‐specific sequence of STEP were required for ERK interaction. In addition to the N‐terminal kinase‐specific sequence region, S245, hydrophobic residues L249/L251, and basic residues R242/R243 located in the KIM region were important in controlling STEP activity toward phospho‐ERK. Further kinetic experiments revealed subtle structural differences between STEP and HePTP that affected the interactions of their KIMs with ERK. Moreover, STEP recognised specific positions of a phospho‐ERK peptide sequence through its active site, and the contact of STEP F311 with phospho‐ERK V205 and T207 were crucial interactions. Taken together, our results not only provide the information for interactions between ERK and STEP, but will also help in the development of specific strategies to target STEP‐ERK recognition, which could serve as a potential therapy for neurological disorders.

     

Benzopyran derivatives from Mallotus apelta

From the leaves of Mallotus apelta, seven benzopyran compounds were obtained and their structures were determined using spectroscopic methods. One showed moderate antibiotic activity against Micrococcus lutens.