Broth rheology and morphological analysis of Solanum chrysotrichum cultivated in a stirred tank

Solanum chrysotrichum cell cultures were grown in a stirred tank bioreactor and their rheological and morphological behaviour were evaluated. The culture broths exhibited non-Newtonian and shear-thinning characteristics. Pseudoplasticity of the broths was governed by their biomass concentration. The roundness of aggregates measured as the elliptical form factor (EFF) had important changes. At the beginning of the culture the aggregates with an EFF lower than 2 represented 52% of the population, but in stationary phase the proportion increased to 77%. Whereas the size of aggregates did not change 80% of the population had an area lower than 0.1 mm². Overall, these results indicate that the shape of the aggregate therefore needs to be considered when studying plant broth rheology.     

Somatic embryogenesis in Eucalyptus globulus

Somatic embryos were obtained from 1% of cotyledon pieces and hypocotyls of mature embryos of Eucalyptus globulus Labill. cultured on media containing a high concentration of picloram or IBA. 2,4-D and other synthetic auxins did not yield somatic embryos or embryogenic callus. Somatic embryos arose indirectly via callus, being visible after four months, and directly, where little callus or adventitious root initiation occurred. Somatic embryos, formed directly from explants, were visible within five weeks. Various structural abnormalities of somatic embryos were observed, especially after induction on media containing picloram. Only two out of fifteen somatic embryos showed hypocotyl and radical elongation, but plantlets did not develop further.     

Distribution of the Coenzyme M Pathway of Epoxide Metabolism among Ethene- and Vinyl Chloride-Degrading Mycobacterium Strains

An epoxyalkane:coenzyme M (CoM) transferase (EaCoMT) enzyme was recently found to be active in the aerobic vinyl chloride (VC) and ethene assimilation pathways of Mycobacterium strain JS60. In the present study, EaCoMT activity and genes were investigated in 10 different mycobacteria isolated on VC or ethene from diverse environmental samples. In all cases, epoxyethane metabolism in cell extracts was dependent on CoM, with average specific activities of EaCoMT between 380 and 2,910 nmol/min/mg of protein. PCR with primers based on conserved regions of EaCoMT genes from Mycobacterium strain JS60 and the propene oxidizers Xanthobacter strain Py2 and Rhodococcus strain B-276 yielded fragments (834 bp) of EaCoMT genes from all of the VC- and ethene-assimilating isolates. The Mycobacterium EaCoMT genes form a distinct cluster and are more closely related to the EaCoMT of Rhodococcus strain B-276 than that of Xanthobacter strain Py2. The incongruence of the EaCoMT and 16S rRNA gene trees and the fact that isolates from geographically distant locations possessed almost identical EaCoMT genes suggest that lateral transfer of EaCoMT among the Mycobacterium strains has occurred. Pulsed-field gel electrophoresis revealed large linear plasmids (110 to 330 kb) in all of the VC-degrading strains. In Southern blotting experiments, the strain JS60 EaCoMT gene hybridized to many of the plasmids. The CoM-mediated pathway of epoxide metabolism appears to be universal in alkene-assimilating mycobacteria, possibly because of plasmid-mediated lateral gene transfer.     

The checkpoint protein Chfr is a ligase that ubiquitinates Plk1 and inhibits Cdc2 at the G2 to M transition.

The checkpoint protein Chfr delays entry into mitosis, in the presence of mitotic stress (Scolnick, D.M., and T.D. Halazonetis. 2000. Nature. 406:430-435). We show here that Chfr is a ubiquitin ligase, both in vitro and in vivo. When transfected into HEK293T cells, Myc-Chfr promotes the formation of high molecular weight ubiquitin conjugates. The ring finger domain in Chfr is required for the ligase activity; this domain auto-ubiquitinates, and mutations of conserved residues in this domain abolish the ligase activity. Using Xenopus cell-free extracts, we demonstrated that Chfr delays the entry into mitosis by negatively regulating the activation of the Cdc2 kinase at the G2-M transition. Specifically, the Chfr pathway prolongs the phosphorylated state of tyrosine 15 in Cdc2. The Chfr-mediated cell cycle delay requires ubiquitin-dependent protein degradation, because inactivating mutations in Chfr, interference with poly-ubiquitination, and inhibition of proteasomes all abolish this delay in mitotic entry. The direct target of the Chfr pathway is Polo-like kinase 1 (Plk1). Ubiquitination of Plk1 by Chfr delays the activation of the Cdc25C phosphatase and the inactivation of the Wee1 kinase, leading to a delay in Cdc2 activation. Thus, the Chfr pathway represents a novel checkpoint pathway that regulates the entry into mitosis by ubiquitin-dependent proteolysis.     

Colonisation of freshwater habitats by the European eel Anguilla anguilla

1. The spatial distribution of European eels in 18 U.K. rivers was related to distance from tidal limit using a negative exponential model. This function accounted for between 19 and 90% of the variation in eel density where quantitative data was available. For semiquantitative data the negative exponential function was a significant predictor of eel densities in only six out of 10 cases, although all rivers showed a consistent decline in abundance with distance upstream from the tidal limit. 2. The spatial distribution of different age groups of European eel in River Severn showed an initial rapid dispersion into freshwater followed by a much slower dispersion rate. Movement of the population upstream by a wave‐form migration process does not occur in this system. Instead colonisation of freshwaters can be seen as a two‐phase dispersion. Phase‐1 is a rapid dispersion upstream driven by density at the point source. Phase‐2 commences once the eels become yellow eels and is equivalent to random diffusion of particles. 3. These processes have important implications for the penetration of freshwaters with reduced numbers of eel larvae arriving on the coast of Europe and North America. Eel abundance will decrease more in freshwaters in an upstream direction whilst it may remain stable or decrease to a lesser extent in estuaries. They are also able to explain the demography of eels migrating upstream over weirs and the observations of varying sex ratios within catchments. We conclude that a dispersion model dependent on age, temperature, difficulty of migration, habitat quality and density of eels should be an important part of freshwater eel management.     

桉树人工林树液流动密度随边材径向深度的变化

树液流动密度 (SFD)随边材径向深度的变化对于准确估测流经边材的树液通量是非常重要的 ,后者又制约着HeatPulse的应用精度。但迄今为止 ,只有很少的研究估计了由于SFD随径向的梯度变化而带来的误差 ,SFD沿树干径向分布规律的获得往往依靠对少数几棵树的观测资料。基于在广东雷州半岛对两块 3～ 4年生桉树 (Euca lyptusurophyllaS .T .Blake)人工林 1年的HeatPulse观测 ,探讨了对来自 39株立木大量观测资料的综合处理方法 ,发现这两个样地 (纪家和河头 )的林分中SFD随边材径向深度的变化可以用如下回归方程来描述 :纪家 :y =3.6 6 75x3 - 7.2 95 5x2 3.6 82 6x 0 .5 6 74 (R2 =0 .9391,n =80 ,P =0 .0 1)河头 :y =5 .0 0 6 2x3 - 9.116 1x2 4.4 5 4 4x 0 .4 6 34(R2 =0 .80 6 9,n =72 ,P =0 .0 1)式中 :y———某一树液感应器所测得的SFD与不同深度的 4个感应器所测得的SFD的平均值之比 ;x—某一树液感应器在边材中的深度与边材厚度之比。从形成层到心材 ,SFD最初有所增加 ,随后持续减小 ,但由于树木年龄很小 ,最大的SFD只比最小的SFD大 0 .33～ 0 .36倍。     

A self-contained system for the field production of plant recombinant interleukin-10

The production of pharmaceutical proteins in plants is creating a broad spectrum of new high-value traits in traditional crop species. As the production of these recombinant proteins moves from bench to field scale, containment and the presence of unwanted secondary metabolites are significant practical issues. We have developed a hybrid male-sterile low-alkaloid tobacco (MSLA) production platform. Recombinant protein is produced in leaves that are harvested prior to flowering. If considered for direct in vivo mammalian use the low-alkaloid background genotype addresses concerns about nicotine, and male sterility further reduces the risk of gene leakage. We have applied this system to the production of human interleukin-10 (phIL-10), a contra-inflammatory cytokine with potential application in the treatment of inflammatory bowel disease and autoimmune diseases. Transgenic low-alkaloid tobacco lines properly assembled a biologically active phIL-10 homodimer. Hybrids made by crossing a single homozygous high-expressing phIL-10 line with a MSLA female were field tested in a high density production system and harvested after 30 days. Recombinant phIL-10 yields were found to be similar in the hybrids and the homozygous control. MSLA tobacco is a practical, self-contained system for the production of plant recombinant proteins.