Frontiers in Biology

ISSN 1674-7984

ISSN 1674-7992(Online)

CN 11-5892/Q

   Online First

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, Volume 5 Issue 6

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HIGHLIGHT
RNA silencing mechanisms are highly differentiated in eukaryotes
Yi ZHANG
Front Biol. 2010, 5 (6): 471-472.  
https://doi.org/10.1007/s11515-010-1170-7

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Posterior to the discovery of the double-stranded RNA mediated gene silencing two decades ago, RNA interference or RNA-mediated gene silencing has received unusual intensity of study in the biology-related research fields. RNA silencing represents a large spectrum of gene regulation mechanisms in all kingdoms of eukaryotes. The power and necessity of RNA silencing has been unambiguously appreciated in both animals and plants, although the mechanisms engaged are divergent in some aspects. Interestingly, as comprehensively reviewed by Schumann et al. in this issue, RNA silencing in the simple eukaryotic fungi strikingly differs from those of animals and plants, and among fungal species as well.

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Innate immune exploitation by a model herpesvirus
Pinghui FENG, Xiaonan DONG
Front Biol. 2010, 5 (6): 473-477.  
https://doi.org/10.1007/s11515-010-0920-x

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REVIEW
RNA silencing in fungi
Ulrike SCHUMANN, Mick AYLIFFE, Kemal KAZAN, Ming-Bo WANG
Front Biol. 2010, 5 (6): 478-494.  
https://doi.org/10.1007/s11515-010-0550-3

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RNA silencing is an evolutionarily conserved mechanism in eukaryotic organisms induced by double-stranded RNA (dsRNA) and plays an essential role in regulating gene expression and maintaining genome stability. RNA silencing occurs at both posttranscriptional levels through sequence-specific RNA degradation or translational repression and at transcriptional levels through RNA-directed DNA methylation and/or heterochromatin formation. RNA silencing pathways have been relatively well characterized in plants and animals, and are now also being widely investigated in diverse fungi, some of which are important plant pathogens. This review focuses primarily on the current understanding of the dsRNA-mediated posttranscriptional gene silencing processes in fungi, but also discusses briefly the known gene silencing pathways that appear to be independent of the RNA silencing machineries. We review RNA silencing studies for a variety of fungi and highlight some of the mechanistic differences observed in different fungal organisms. As RNA silencing is being exploited as a technology in gene function studies in fungi as well as in engineering anti-fungal resistance in plants and animals, we also discuss the recent progress towards understanding dsRNA uptake in fungi.

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Two-component signal transduction systems and regulation of virulence factors in Xanthomonas: a perspective
Fang-Fang WANG, Li WANG, Wei QIAN
Front Biol. 2010, 5 (6): 495-506.  
https://doi.org/10.1007/s11515-010-0750-x

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Two-component signal transduction systems (TCSTSs), consisting of a histidine kinase and a response regulator, play a critical role in regulating virulence gene expression in Gram-negative phytopathogenic bacteria Xanthomonas spp.. To date, 12 TCSTS genes have been identified, accounting for approximately 10% of the TCSTS genes in each genome that have been experimentally identified to be related to pathogenesis. These TCSTSs modulate the expression of a number of virulence factors through diverse molecular mechanisms such as interacting with DNA, protein-binding and involvement in second messenger metabolism, which generates a high level of regulatory versatility. Here we summarize the current knowledge in this field and discuss the emerging themes and remaining questions that are important in deciphering the signaling network of TCSTSs in Xanthomonas.

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Cross-talking between autophagy and viral infection in mammalian cells
Hongya HAN, Lishu ZHANG, Xinxian DAI, Yanpeng ZHENG
Front Biol. 2010, 5 (6): 507-515.  
https://doi.org/10.1007/s11515-010-0760-8

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Autophagy is a cellular process in degradation of long-lived proteins and organelles in the cytosol for maintaining cellular homeostasis, which has been linked to a wide range of human health and disease states, including viral infection. The viral infected cells exhibit a complicated cross-talking between autophagy and virus. It has been shown that autophagy interacts with both adaptive and innate immunity. For adaptive immunity, viral antigens can be processed in autophagosomes by acidic proteases before major histocompatibility complex (MHC) class II presentation. For innate immunity, autophagy may assist in the delivery of viral nucleic acids to endosomal TLRs and also functions as a part of the TLR-or-PKR-downstream responses. Autophagy was also reported to suppress the magnitude of host innate antiviral immunity in certain cases. On the other hand, viruses has evolved many strategies to combat or utilize the host autophagy for their own benefit. In this review we discussed recent advances toward clarifying the cross-talking between autophagy and viral infection in mammalian cells.

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Heme regulates protein homeostasis at transcription, protein translation, and degradation levels
Fang YANG, En-Duo WANG
Front Biol. 2010, 5 (6): 516-523.  
https://doi.org/10.1007/s11515-010-7700-5

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Heme, as a prosthetic group of proteins, is an iron-protoporphyrin involved in a wide range of cellular functions. Cellular heme levels vary due to the accurate balance of its synthesis and degradation. The “heme sensor protein” is currently a focus of investigation because heme has been found as a cellular signaling messenger involved in various biologic processes, including gene expression, protein localization, protein stability and microRNA processing. Several eukaryotic transcriptional factors can be regulated by heme, including heme activator protein (Hap1), Bach1, REV-erbα, and neuronal PAS domain protein 2 (NPAS2). Especially, the two circadian transcriptional factors serving as the heme sensor, REV-erbα and NPAS2, coordinate the circadian clock with metabolic pathways. It is well established that heme regulates the activity of heme-regulated eukaryotic initiation factor 2α (eIF2α) kinase (HRI), which serves as a feedback inhibitor of protein translation in both erythroid and non- erythroid cells. Additionally, heme is involved in protein degradation by inducing the degradation of several proteins such as the iron response regulator (Irr), iron regulatory protein 2 (IRP2), Bach1, and circadian factor period 2 (Per2). The N-end rule ubiquitin-dependent protein degradation pathway has also been identified as a sensor of heme, which blocks the function of arginyl-tRNA protein transferase (ATE1) and E3 ubiquitin ligase. In this review, we summarize the regulatory roles of heme at the levels of transcription, protein translation, and protein degradation, highlighting the role of heme in maintaining cellular homeostasis.

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Advances in genomic study of cortical projection neurons
Chunsheng QU, Jieguang CHEN
Front Biol. 2010, 5 (6): 524-531.  
https://doi.org/10.1007/s11515-010-0670-9

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The mammalian neocortex gives rise to perception and initiates voluntary motor responses. The cortical laminae are comprised of six distinct cellular layers of local circuit neurons and projection neurons. To explore molecular identities of the distinct cortical projection neurons, discovery-orientated genomic approaches have been adopted. Microarray analysis of dissected cortical tissues has been applied to identify cortical layer markers. Early neuronal cells were sorted by FACS from GFP-labeled embryonic brains for gene expression profiling. Laser capture microdissection of retrograde-labeled projection neurons, when coupled with optimal RNA amplification technology, has become a valuable strategy for neuronal isolation and gene expression analysis in differentiated neurons. RNA sequencing technology is promising not only for the determination of gene expression, but also for discovery of posttranscriptional modifications of the complex neural system. There is no doubt that advances in genomic studies are opening up novel research avenues for our understanding of the cortical neuronal functions.

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Melatonin and mitochondria in aging
Weiguo DONG, Fang HUANG, Hongwen HE
Front Biol. 2010, 5 (6): 532-539.  
https://doi.org/10.1007/s11515-010-0730-1

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The worldwide prolongation of mean life expectancy has resulted in a rapid increase of the size of the elderly population, both in numbers and as a proportion of the whole. In addition, the incidence of age-related diseases is obviously increasing as the population ages. Finding means to preserve optimal health in old age has become a primary goal of biomedical research. Aging is a multifactorial process that includes progressive cellular loss, endocrine and metabolic deficits, reduced defense mechanisms and functional losses that increase the risk of death. Mitochondria fulfill a number of essential cellular functions and play a key role in the aging process. Melatonin, which is synthesized in the pineal gland and other organs, plays a role in the biologic regulation of aging. Noctural melatonin serum levels are high during childhood and diminish substantially as people age. Melatonin preserves mitochondrial homeostasis, reduces free radical generation, e.g., by enhancing mitochondrial glutathione levels; it also safeguards proton potential and ATP synthesis by stimulating complex I and IV activities. In this article, we review the role of melatonin and mitochondria in aging.

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Oridonin: A promising anticancer drug from China
Wenjing ZHANG, Qilai HUANG, Zi-Chun HUA
Front Biol. 2010, 5 (6): 540-545.  
https://doi.org/10.1007/s11515-010-0610-8

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Oridonin, a diterpenoid isolated from Rabdosia rubescens (Hemsl.) Hara, has been proved to possess remarkable anticancer activity, in addition to its potential in antiinflammation and antibacteria. The purpose of this article is to review current progress in oridonin concerned about a relationship between the chemical structure/modifications and its anticancer activity and to discuss the molecular mechanisms underlying its anticancer activity, such as suppression of tumor proliferation and induction of tumor cell death, and the cell signal transduction in anticancer activity of oridonin.

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RESEARCH ARTICLE
Comparative analysis of panicle proteomes of two upland rice varieties upon hyper-osmotic stress
Wei HUANG, Ting BI, Weining SUN
Front Biol. 2010, 5 (6): 546-555.  
https://doi.org/10.1007/s11515-010-0720-3

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Drought is a major environmental factor that limits the yield of rice dramatically. Upland rice is now regarded as a promising rice cultivar in water saving agriculture. Two varieties of upland rice Zhonghan 3 and IR29 were used to compare the physiological and proteomic responses to hyper-osmotic stress induced by 15% polyethyleneglycol (PEG) at the reproductive stage. Osmotic stress affected the growth development and caused the loss of production especially the grain yield. IR29 was more tolerant to PEG than Zhonghan 3 as shown by less yield loss under osmotic stress conditions. Comparative proteomic analysis of the panicle suggested that the up-regulation of glycolysis related proteins and defense proteins may contribute to the better osmotic tolerance in IR29.

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Behavioural responses of ex-situ captive hippopotamus (Hippopotamus amphibius) in lactation season: Maternal investment and plasticity of infant self-independence
Wei CHEN, Mallikarjun P. HANDIGUND, Jinghua MA, Lucia Lopez LOPEZ, Xianfu ZHANG
Front Biol. 2010, 5 (6): 556-563.  
https://doi.org/10.1007/s11515-010-0540-5

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In order to promote hippopotamus management in the captive and ex-situ environment, especially the control of behavioural and physiological status during breeding and lactation seasons, we conducted a preliminary study on behavioural responses of a pair of hippos including both mother and infant in Hangzhou Wildlife Park, China. The study of the captive hippos for about 1-month in the lactation season was carried out during August and September, 2009. The behavioural patterns were identified by all occurrence sampling and instantaneous scanning sampling methods with 5–10 min intervals. As a result, mother-offspring conflicts and interactions did occur throughout the whole study period. Early maternal investment showed a positive trend in activity rhythms (slope= 0.0014, Z = 0.3027, P<0.001) and a negative trend (slope= -0.0066, Z = 0.8807, P<0.001) in territorial occupation of water, all of which supported our hypotheses that the mother hippo might exert less care for the infant and cut down on her own obligations in nursing. For infant self-independence, during the whole lactation season, the primary trends of activities and territorial occupation dynamics of the infant hippo were slightly different from before, judging from linear models (slope= -0.0017, Z = 0. 3309, P<0.001). However, the frequencies of activities were not stable, especially at around 12 days of age. The trends of territorial occupation (slope= -0.0071, Z = 0. 904, P<0.001) also showed negative dynamics in water body occupation by the time the infant hippo grew up. The general trend (slope= -0.005, Z = 0.06, P<0.001) of suckling dynamics was demonstrably negative, with an upwards fluctuation at period 3 (10–15th day). This also illustrated that as the infant developed, the dependency on the mother was reduced at the end of the lactation season. In addition, a sharp decline between P3 and P4 also supported the mother-offspring conflict theory. In general, time budgets of hippos in active behaviour were (31.8±2.1)% for the mother and (32.1±2.6)% for the infant. Spatial distributions in water within temporal limitations were (80.1±2.7)% for the mother and (81.8±2.7)% for the infant. Behavioural dynamics showed strong synchronous relations between maternal investment and infant independence. Our current short-term investigation proves to be a key in management and conservation of hippopotami during the lactation season.

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11 articles