RIG‐I detects infection with live Listeria by sensing secreted bacterial nucleic acids

Immunity against infection with Listeria monocytogenes is not achieved from innate immune stimulation by contact with killed but requires viable Listeria gaining access to the cytosol of infected cells. It has remained ill‐defined how such immune sensing of live Listeria occurs. Here, we report that efficient cytosolic immune sensing requires access of nucleic acids derived from live Listeria to the cytoplasm of infected cells. We found that Listeria released nucleic acids and that such secreted bacterial RNA/DNA was recognized by the cytosolic sensors RIG‐I, MDA5 and STING thereby triggering interferon β production. Secreted Listeria nucleic acids also caused RIG‐I‐dependent IL‐1β‐production and inflammasome activation. The signalling molecule CARD9 contributed to IL‐1β production in response to secreted nucleic acids. In conclusion, cytosolic recognition of secreted bacterial nucleic acids by RIG‐I provides a mechanistic explanation for efficient induction of immunity by live bacteria.     

Autophagy targeting of Listeria monocytogenes and the bacterial countermeasure

Autophagy acts as an intrinsic defense system against intracellular bacterial survival. Recently, multiple cellular pathways that target intracellular bacterial pathogens to autophagy have been described. These include the Atg5/LC3 pathway, which targets Shigella, the ubiquitin (Ub)-NDP52-LC3 pathway, which targets Group A Streptococcus (GAS) and Salmonella typhimurium, the Ub-p62-LC3 pathway, which targets Mycobacterium tuberculosis, Listeria monocytogenes and S. typhimurium, and the diacylglycerol-dependent pathway, which targets S. typhimurium. In addition, the bacterial invasion process is targeted by the NOD1 or NOD2-Atg16LLC3 pathway. Bacterial pathogens with an intracytosolic lifestyle, i.e., those capable of inducing actin polymerization and cell-to-cell spreading, also employ diverse tactics to evade autophagic recognition. Thus, Shigella, L. monocytogenes and Burkholderia pseudomallei deploy highly evolved systems to evade autophagic recognition and growth restriction. Here, we briefly review current knowledge of host recognition of L. monocytogenes by the innate immune system, and highlight how autophagic recognition by the host is overcome by bacterial countermeasures.     

苦荞黄酮-3-羟化酶截短体的原核表达与多克隆抗体制备

为了制备苦荞黄酮-3-羟化酶的多克隆抗体,该研究以苦荞种子灌浆期cDNA文库中获得的苦荞黄酮-3-羟化酶基因截短体(truncated Flavanone-3-hydroxylase,TrF3 H)序列为基础,采用PCR扩增F3 H的截短序列编码区(TrF3 H),构建了原核表达载体pET47b-TrF3 H,并转化入大肠杆菌Rosetta(DE3)plysS中进行诱导表达,将经钴离子螯合层析柱纯化后的目的蛋白切胶回收后制备了高效价的多克隆抗体。结果表明:pET47b-TrF3 H在大肠杆菌Rosetta(DE3)plysS中以包涵体的形式高效表达。蛋白质印迹显示,制备的多克隆抗体能特异识别其对应的抗原,天然的黄酮-3-羟化酶蛋白在苦荞的未成熟种子中大量表达。原核表达体系的建立和多克隆抗体的制备为进一步探讨F3H在苦荞中功能奠定了基础。     

The diageotropica mutation alters auxin induction of a subset of the Aux/IAA gene family in tomato

The diageotropica (dgt) mutation has been proposed to affect either auxin perception or responsiveness in tomato plants. It has previously been demonstrated that the expression of one member of the Aux/IAA family of auxin-regulated genes is reduced in dgt plants. Here, we report the cloning of ten new members of the tomato Aux/IAA family by PCR amplification based on conserved protein domains. All of the gene family members except one (LeIAA7) are expressed in etiolated tomato seedlings, although they demonstrate tissue specificity (e.g. increased expression in hypocotyls vs. roots) within the seedling. The wild-type auxin-response characteristics of the expression of these tomato LeIAA genes are similar to those previously described for Aux/IAA family members in Arabidopsis. In dgt seedlings, auxin stimulation of gene expression was reduced in only a subset of LeIAA genes (LeIAA5, 8, 10, and 11), with the greatest reduction associated with those genes with the strongest wild-type response to auxin. The remaining LeIAA genes tested exhibited essentially the same induction levels in response to the hormone in both dgt and wild-type hypocotyls. These results confirm that dgt plants can perceive auxin and suggest that a specific step in early auxin signal transduction is disrupted by the dgt mutation.     

Central adaptation models of the vestibulo-ocular and optokinetic systems

A theoretical analysis of two models of the vestibulo-ocular and optokinetic systems was performed. Each model contains a filter element in the vestibular periphery to account for peripheral adaptation, and a filter element in the central vestibulooptokinetic circuit to account for central adaptation. Both models account for1 adaptation, i.e. a response decay to a constant angular acceleration input, in both peripheral vestibular afferent and vestibulo-ocular reflex (VOR) responses and2 the reversal phases of optokinetic after-nystagmus (OKAN) and the VOR and3 oscillatory behavior such as periodic alternating nystagmus. The two models differ regarding the order of their VOR transfer function. Also, they predict different OKAN patterns following a prolonged optokinetic stimulus. These models have behavioral implications and suggest future experiments.     

Localisation of carcinoembryonic antigen in embryonic and fetal human tissues

Carcinoembryonic antigen (CEA) was localized in various embryonic and fetal human tissues between 8 and 16 weeks of gestation as well as in the colorectal mucosa of older fetuses, newborns and adults. Among the embryonic tissues, CEA was always present in the esophagus, the gastric antrum, the duodenum and the rectum. CEA positive staining of bile canaliculi of the liver was inconstant. All other embryonic tissues were CEA negative. During early fetal development, CEA positive staining of the esophagus, antrum and duodenum was inconstant. However, the whole colon became intensively stained. An inconstant CEA specific staining was found in parts of the midgut and in the bile canaliculi of the liver. The other organs remained CEA negative. Between the 17th week of gestation and birth, CEA staining pattern of the colorectal mucosa did not change. The staining intensity of late fetal colonic mucosa was similar to that of adult colonic mucosa.