细叶黄芪叶肉原生质体植株再生

从细叶黄芪(Astragalus tenuis)外植体愈伤组织分化出的再生苗叶片分离原生质体。原生质体培养在改良 K8p 培养基中形成了愈伤组织。增殖后的愈伤组织转入分化培养基中分化出苗。幼苗在生根培养基中长出不定根,再生成为完整植株。再生苗叶肉原生质体在 AY培养基中,种子无菌苗叶肉原生质体在改良 K8p 或 AY 培养基中均不能形成愈伤组织。较低的2,4-D 浓度有利于原生质体愈伤组织的形成和分化,过高的2,4-D 浓度对愈伤组织的形成和分化有不利的影响。     

小冰麦异附加系中天兰冰草染色体的变异

通过对两套14种小冰麦异附加系的体细胞染色体观察,发现3个异附加系各有1对染色体发生了显著变异。其中TAl-14t有1对端着丝点染色体,TAl-22s和TAl-27s各有1对近中着丝点的小染色体。通过组胞遗传学分析,从3个方面证明了发生变异的染色体均来自天兰冰草。此外还发现在其中的两个异附加系(TAI-14t和TAl-27s)中可能产生了自发易位。     

天蓝苜蓿单细胞培养植株再生

采用了改良K8p和Ay3两种培养基,对天蓝苜蓿进行单细胞培养并得到再生植株。来自天蓝苜蓿胚轴愈伤组织的细胞系,在单细胞培养中的愈伤组织分化率明显高于来自子叶愈伤组织的细胞系。改良K8p培养基较之Ay3培养基更利于天蓝苜蓿单细胞培养。生物素、泛酸钙和葡萄糖对细胞系的细胞分裂、愈伤组织诱导和分化有促进作用。赤霉素促进再生幼芽向植株发育。     

Dogs lacking Apolipoprotein E show advanced atherosclerosis leading to apparent clinical complications

Science China Life Sciences - Atherosclerotic cardiovascular disease resulting from dysregulated lipid metabolism is the leading cause of morbidity and mortality worldwide. Apolipoprotein E (ApoE)...     

PtdIns4P synthesis by PI4KIIIα at the plasma membrane and its impact on plasma membrane identity

Plasma membrane phosphatidylinositol (PI) 4-phosphate (PtdIns4P) has critical functions via both direct interactions and metabolic conversion to PI 4,5-bisphosphate (PtdIns(4,5)P₂) and other downstream metabolites. However, mechanisms that control this PtdIns4P pool in cells of higher eukaryotes remain elusive. PI4KIIIα, the enzyme thought to synthesize this PtdIns4P pool, is reported to localize in the ER, contrary to the plasma membrane localization of its yeast homologue, Stt4. In this paper, we show that PI4KIIIα was targeted to the plasma membrane as part of an evolutionarily conserved complex containing Efr3/rolling blackout, which we found was a palmitoylated peripheral membrane protein. PI4KIIIα knockout cells exhibited a profound reduction of plasma membrane PtdIns4P but surprisingly only a modest reduction of PtdIns(4,5)P₂ because of robust up-regulation of PtdIns4P 5-kinases. In these cells, however, much of the PtdIns(4,5)P₂ was localized intracellularly, rather than at the plasma membrane as in control cells, along with proteins typically restricted to this membrane, revealing a major contribution of PI4KIIIα to the definition of plasma membrane identity.     

Triacylglycerol Utilization Is Required for Regrowth of In Vitro Hypoxic Nonreplicating Mycobacterium bovis Bacillus Calmette-Guerin

Mycobacteria store triacylglycerols (TGs) under various stress conditions, such as hypoxia, exposure to nitric oxide, and acidic environments. These stress conditions are known to induce nonreplicating persistence in mycobacteria. The importance of TG accumulation and utilization during regrowth is not clearly understood. Here we specifically determined the levels of accumulated TG and TG lipase activity in Mycobacterium bovis bacillus Calmette-Guerin (BCG) in various different physiological states (logarithmic growth, aerated stationary phase, hypoxia-induced dormancy, and regrowth from dormancy). We found extensive accumulation and degradation of TGs in the bacilli during entry into and exit from hypoxia-induced dormancy, respectively. These processes are accompanied by dynamic appearance and disappearance of intracellular TG lipid particles. The reduction in TG levels coincides with an increase in cellular TG lipase activity in the regrowing bacilli. Tetrahydrolipstatin, an inhibitor of TG lipases, reduces total lipase activity, prevents breakdown of TGs, and blocks the growth of mycobacteria upon resuscitation with air. Our results demonstrate that utilization of TGs is essential for the regrowth of mycobacteria during their exit from the hypoxic nonreplicating state.Mycobacterium tuberculosis is the causative agent of tuberculosis (TB), one of the major infectious diseases, which affects one-third of the world''s population (http://www.who.int/mediacentre/factsheets/fs104/en/). The majority of TB patients carry a latent infection. However, reactivation leading to active disease (16, 27) often occurs once the host defenses are weakened. During the latency period, mycobacteria are tolerant to many conventional antibiotics (23, 28), thus making eradication of TB challenging.In the human body, M. tuberculosis is believed to persist in lung lesions with hypoxic environments (6, 27). Wayne and Hayes established an “in vitro dormancy model” in which mycobacterial cultures are subjected to gradual depletion of oxygen, which causes the obligate aerobic cells to exit the cell cycle and enter into a nonreplicating persistent state (26). The bacilli in the nonreplicating persistent state are phenotypically drug resistant. Recent efforts to explore the mechanisms which allow the tubercle bacilli to enter into dormancy and survive in the host for a long period of time suggest that fatty acids (FAs) could be an important source of energy during the persistent state (1, 17, 20). In particular, triacylglycerols (TGs), a class of neutral lipids, are postulated to be a likely source of FAs (8). TGs are an efficient form of energy reserves in many organisms during long-term survival.Recently, it was reported that tubercle bacilli in sputum from patients with TB contain lipid bodies (11). Moreover, TGs accumulate in hypervirulent W-Beijing strains of M. tuberculosis (19). It is interesting that TGs accumulate in these clinical strains of TB. However, no systematic study has been carried out yet to investigate the accumulation and degradation of TG species under various physiological conditions in mycobacteria. Here we used M. bovis bacillus Calmette-Guerin (BCG) to study the kinetics of TG buildup and breakdown during different growth phases, including logarithmic growth, aerated stationary phase, hypoxia-induced dormancy (Wayne model), and regrowth from dormancy upon reaeration of hypoxic cultures. Utilizing tetrahydrolipstatin (THL) as a chemical probe, we showed that mobilization of TGs is essential for the regrowth of mycobacteria during recovery from the hypoxia-induced dormant state.     

Molecular identification of the gene encoding porcine tristetraprolin (TTP)

Tristetraprolin (TTP) is a CCCH tandem zinc finger protein that can bind to and destabilize certain mRNAs containing AU-rich element (ARE) binding sites. In this study, a novel porcine cDNA has been isolated by expressed sequence tag assembly and subsequently confirmed by RT-PCR analysis, and designated porcine TTP (poTTP). The open reading frame of the poTTP cDNA is 981 bp, encoding 326 amino acids. The poTTP gene is approximately 2.5 kb in size and contains a single intron. Southern blotting analysis demonstrated that it is a single copy gene. Real-time quantitative PCR analysis revealed that the poTTP gene is constitutively expressed in all detected tissues, and with the highest mRNA level in lymphoid tissues spleen and thymus. Recombinant His₆-tagged poTTP protein and its two zinc finger mutants (C146G and H127I) were efficiently expressed and purified from Escherichia coli BL21 (DE3), respectively. In vitro, RNA-electrophoretic mobility shift assay confirmed a direct interaction between poTTP protein and porcine TNF-α (poTNF-α) mRNA ARE probe; this interaction was eliminated when using either two zinc finger mutants of poTTP. Consistently, mutations within the ARE region prevented the binding interaction between recombinant poTTP protein and poTNF-α mRNA ARE probe. These results indicate that poTTP is an ARE-binding protein that might regulate the turnover of certain mRNAs in vivo.