开启防御之门: 植物抗病小体

NLR蛋白是存在于植物和动物中的一个免疫受体大家族, 具有核苷酸结合域并富含亮氨酸重复序列。植物NLR通过识别病原菌特异效应子开启免疫信号转导。第1个植物NLR抗性蛋白于25年前克隆, 但其激活机制仍不清楚, 至今仍未获得一个完整的NLR蛋白结构。最近, 柴继杰、周俭民和王宏伟实验室合作解析了第一个植物完整NLR ZAR1激活前后的结构, 研究成果以两篇论文形式发表在“科学”杂志上, 填补了NLR介导的免疫信号转导研究领域的空白。该文简要总结了相关研究进展, 讨论了NLR免疫信号转导研究领域尚需解决的问题。     

稻田生物群落的能流参数

为了从能流动态来研究稻田生物群落,本文用田间调查和实验室测定等方法,取得了晚稻田生物群落的物种数量、生物量、热值、呼吸量、生产力、同化效率、摄食量等数据。据此,进一步估算了晚稻田生物群落的能量流动参数。根据其能量收支,用能量金字塔总结了晚稻田生物群落各类种群间的能量关系。     

HBsAg阴性母亲的新生儿接种不同剂量乙型肝炎血源疫苗的效果

HBsAg阴位母亲的新生儿,按0,1、6月程序分别接种10-10-10μg(1组)、20-10-10μg(2组)和30-10-10μg(3组)乙型肝炎血源疫苗。第一针后一年,检查抗-HBs阳转率,分别为87.60％,90.64％和88.97％,无统计学显著差异。3针10μg组免疫后l～4年抗-HBs阳性率分别为88.31％、81.08％、80.10％和78.39％,虽稍下降,但无统计学显著差异。3个剂量组HBsAg阳性率分别为0.71％,0.49％和0.74％,说明HBsAg阴性母亲的新生儿,用国产血源HBsAg疫苗免疫以10μ×3效果较理想。     

Circular RNA AFF4 modulates osteogenic differentiation in BM-MSCs by activating SMAD1/5 pathway through miR-135a-5p/FNDC5/Irisin axis

Bone marrow-derived mesenchymal stem cells (BM-MSCs), the common progenitor cells of adipocytes and osteoblasts, have been recognized as the key mediator during bone formation. Herein, our study aim to investigate molecular mechanisms underlying circular RNA (circRNA) AFF4 (circ_AFF4)-regulated BM-MSCs osteogenesis. BM-MSCs were characterized by FACS, ARS, and ALP staining. Expression patterns of circ_AFF4, miR-135a-5p, FNDC5/Irisin, SMAD1/5, and osteogenesis markers, including ALP, BMP4, RUNX2, Spp1, and Colla1 were detected by qRT-PCR, western blot, or immunofluorescence staining, respectively. Interactions between circ_AFF4 and miR-135a-5p, FNDC5, and miR-135a-5p were analyzed using web tools including TargetScan, miRanda, and miRDB, and further confirmed by luciferase reporter assay and RNA pull-down. Complex formation between Irisin and Integrin αV was verified by Co-immunoprecipitation. To further verify the functional role of circ_AFF4 in vivo during bone formation, we conducted animal experiments harboring circ_AFF4 knockdown, and born samples were evaluated by immunohistochemistry, hematoxylin and eosin, and Masson staining. Circ_AFF4 was upregulated upon osteogenic differentiation induction in BM-MSCs, and miR-135a-5p expression declined as differentiation proceeds. Circ_AFF4 knockdown significantly inhibited osteogenesis potential in BM-MSCs. Circ_AFF4 stimulated FNDC5/Irisin expression through complementary binding to its downstream target molecule miR-135a-5p. Irisin formed an intermolecular complex with Integrin αV and activated the SMAD1/5 pathway during osteogenic differentiation. Our work revealed that circ_AFF4, acting as a sponge of miR-135a-5p, triggers the promotion of FNDC5/Irisin via activating the SMAD1/5 pathway to induce osteogenic differentiation in BM-MSCs. These findings gained a deeper insight into the circRNA-miRNA regulatory system in the bone marrow microenvironment and may improve our understanding of bone formation-related diseases at physiological and pathological levels.Subject terms: Stem cells, Diseases     

A 3-hydroxy-3-methylglutaryl-CoA synthase-based probe for the discovery of the acyltransferase-less type I polyketide synthases

Acyltransferase (AT)-less type I polyketide synthases (PKSs) produce complex natural products due to the presence of many unique tailoring enzymes. The 3-hydroxy-3-methylglutaryl coenzyme A synthases (HCSs) are responsible for β-alkylation of the growing polyketide intermediates in AT-less type I PKSs. In this study, we discovered a large group of HCSs, closely associated with the characterized and orphan AT-less type I PKSs through in silico genome mining, sequence and genome neighbourhood network analyses. Using HCS-based probes, the survey of 1207 in-house strains and 18 soil samples from different geographic locations revealed the vast diversity of HCS-containing AT-less type I PKSs. The presence of HCSs in many AT-less type I PKSs suggests their co-evolutionary relationship. This study provides a new probe to study the abundance and diversity of AT-less type I PKSs in the environment and microbial strain collections. Our study should inspire future efforts to discover new polyketide natural products from AT-less type I PKSs.     

Bioactive terpenoids from Euonymus verrucosus var. pauciflorus showing NO inhibitory activities

In our continuous search for new nitric oxide (NO) inhibitory compounds as potential anti-inflammatory agents or lead compounds for inflammatory diseases, the chemical constituents of Euonymus verrucosus var. pauciflorus were investigated, leading to the isolation of eleven terpenoids including six new diterpenoids, designated as euonymupenes A–F. The structures were elucidated on the basis of NMR and ECD data analysis. Euonymupenes A, C, and F feature rare labdane-type norditerpenoid skeletons. The NO inhibitory effects were evaluated and all of the isolates were found to inhibit lipopolysaccharide (LPS)-induced NO production in murine microglial BV-2 cells. Western blotting analysis indicated that the most active compound (5) can regulate iNOS (inducible nitric oxide synthase) expression. The further molecular docking studies exhibited the affinities of bioactive compounds with iNOS.