Amplified Fragment Length Polymorphism Fingerprinting of 16 Banana Cultivars (Musa cvs.)

Banana is one of the most important subtropical crops. The genetic system, however, is relatively unknown and is complicated by specific interhybridization, heterozygosity, and polyploidy, which are common in most clones. These factors make identification of closely related banana cultivars difficult, particularly when sterile. Amplified fragment length polymorphism (AFLP) analysis using eight primer combinations was carried out on 16 banana cultivars. Results showed that AFLP could be used to distinguish the different cultivars by their unique banding patterns. Unique AFLP molecular markers were detected for 12 banana cultivars, which can be used to develop specific probes for identification purposes. The cluster analysis also revealed the need for a link between genotype studies using molecular techniques and the current system of classification of Musa cultivars based purely on morphological traits.     

Impact of fumigants on soil microbial communities.

Agricultural soils are typically fumigated to provide effective control of nematodes, soilborne pathogens, and weeds in preparation for planting of high-value cash crops. The ability of soil microbial communities to recover after treatment with fumigants was examined using culture-dependent (Biolog) and culture-independent (phospholipid fatty acid [PLFA] analysis and denaturing gradient gel electrophoresis [DGGE] of 16S ribosomal DNA [rDNA] fragments amplified directly from soil DNA) approaches. Changes in soil microbial community structure were examined in a microcosm experiment following the application of methyl bromide (MeBr), methyl isothiocyanate, 1,3-dichloropropene (1,3-D), and chloropicrin. Variations among Biolog fingerprints showed that the effect of MeBr on heterotrophic microbial activities was most severe in the first week and that thereafter the effects of MeBr and the other fumigants were expressed at much lower levels. The results of PLFA analysis demonstrated a community shift in all treatments to a community dominated by gram-positive bacterial biomass. Different 16S rDNA profiles from fumigated soils were quantified by analyzing the DGGE band patterns. The Shannon-Weaver index of diversity, H, was calculated for each fumigated soil sample. High diversity indices were maintained between the control soil and the fumigant-treated soils, except for MeBr (H decreased from 1.14 to 0.13). After 12 weeks of incubation, H increased to 0.73 in the MeBr-treated samples. Sequence analysis of clones generated from unique bands showed the presence of taxonomically unique clones that had emerged from the MeBr-treated samples and were dominated by clones closely related to Bacillus spp. and Heliothrix oregonensis. Variations in the data were much higher in the Biolog assay than in the PLFA and DGGE assays, suggesting a high sensitivity of PLFA analysis and DGGE in monitoring the effects of fumigants on soil community composition and structure. Our results indicate that MeBr has the greatest impact on soil microbial communities and that 1,3-D has the least impact.     

甘蔗节间伸长过程赤霉素生物合成关键基因的表达及相关植物激素动态变化

以甘蔗(Saccharum officinarum)优良品种桂糖42号(GT42)为研究材料, 分别于未伸长期(9-10叶龄以前) (Ls1)、伸长初期(12-13叶龄) (Ls2)和伸长盛期(15-16叶龄) (Ls3)取甘蔗第2片真叶(自顶部起)对应的节间组织, 测定其赤霉素(GA)、生长素(IAA)、油菜素甾醇(BR)、细胞分裂素(CTK)、乙烯(ETH)和脱落酸(ABA)的含量, 并通过实时荧光定量PCR (qRT-PCR)分析赤霉素合成途径关键基因GA₂₀氧化酶基因(GA20-Oxidase1)、赤霉素受体基因(GID1)和DELLA蛋白编码基因(GAI)的差异表达。结果表明, 在甘蔗伸长期间, GA和IAA含量呈现上升趋势, CTK和ABA含量呈下降趋势, ETH含量先上升后下降, BR含量则变化不明显; GA20-Oxidase1和GID1的表达呈上升趋势, 而GAI的表达则呈下降趋势, 这与相关植物激素的变化基本一致。综上, 甘蔗节间伸长过程主要与GA和IAA相关, 其次为CTK和ABA, 而ETH受到IAA的调控影响节间伸长; 植物激素间通过相互作用调控GA20-Oxidase1、GID1和GAI的表达, 影响GA含量和GA的信号转导过程, 进而影响甘蔗节间的伸长。该研究揭示了甘蔗节间伸长过程中赤霉素生物合成途径和信号转导关键基因的差异表达及植物激素含量的动态变化规律。     

Crystal structure at 2.8 A of an FcRn/heterodimeric Fc complex: mechanism of pH-dependent binding

The neonatal Fc receptor (FcRn) transports immunoglobulin G (IgG) across epithelia, binding IgG in acidic vesicles (pH < or = 6.5) and releasing IgG in the blood at pH 7.4. Well-ordered FcRn/Fc crystals are prevented by the formation of "oligomeric ribbons" of FcRn dimers bridged by Fc homodimers, thus we crystallized a 1:1 complex between rat FcRn and a heterodimeric Fc containing only one FcRn binding site. The 2.8 A complex structure demonstrates that FcRn uses its alpha2 and beta2-microglobulin domains and carbohydrate to interact with the Fc C(gamma)2-C(gamma)3 interface. The structure reveals conformational changes in Fc and three titratable salt bridges that confer pH-dependent binding, and can be used to guide rational design of therapeutic IgGs with longer serum half-lives.     

New pollen classification of Chenopodiaceae for exploring and tracing desert vegetation evolution in eastern arid central Asia

Members of the Chenopodiaceae are the most dominant elements in the central Asian desert. The different genera and species within this family are common in desert vegetation types. Should it prove possible to link pollen types in this family to specific desert vegetation, it would be feasible to trace vegetation successions in the geological past. Nevertheless, the morphological similarity of pollen grains in the Chenopodiaceae rarely permits identification at the generic level. Although some pollen classifications of Chenopodiaceae have been proposed, none of them tried to link pollen types to specific desert vegetation types in order to explore their ecological significance. Based on the pollen morphological characters of 13 genera and 24 species within the Chenopodiaceae of eastern central Asia, we provide a new pollen classification of this family with six pollen types and link them to those plant communities dominated by Chenopodiaceae, for example, temperate dwarf semi‐arboreal desert (Haloxylon type), temperate succulent halophytic dwarf semi‐shrubby desert (Suaeda, Kalidium, and Atriplex types), temperate annual graminoid desert (Kalidium type), temperate semi‐shrubby and dwarf semi‐shrubby desert (Kalidium, Iljini, and Haloxylon types), and alpine cushion dwarf semi‐shrubby desert (Krascheninnikovia type). These findings represent a new approach for detecting specific desert vegetation types and deciphering ecosystem evolution in eastern central Asia.     

Proteomic analysis of Saccharomyces cerevisiae under high gravity fermentation conditions

Saccharomyces cerevisiae KAY446 was utilized for ethanol production, with glucose concentrations ranging from 120 g/L (normal) to 300 g/L (high). Although grown in a high glucose environment, S. cerevisiae still retained the ability to produce ethanol with a high degree of glucose utilization. iTRAQ-mediated shotgun proteomics was applied to identify relative expression change of proteins under the different glucose conditions. A total of 413 proteins were identified from three replicate, independent LC-MS/MS runs. Unsurprisingly, many proteins in the glycolysis/gluconeogenesis pathway showed significant changes in expression level. Twenty five proteins involved in amino acid metabolism decreased their expression, while the expressions of 12 heat-shock related proteins were also identified. Under high glucose conditions, ethanol was produced as a major product. However, the assimilation of glucose as well as a number of byproducts was also enhanced. Therefore, to optimize the ethanol production under very high gravity conditions, a number of pathways will need to be deactivated, while still maintaining the correct cellular redox or osmotic state. Proteomics is demonstrated here as a tool to aid in this forward metabolic engineering.     

Molecular typing of Salmonella enterica serovar Sofia in Australia by pulsed‐field gel electrophoresis and repetitive element PCR typing

Aims: In this study, we used two molecular fingerprinting methods to investigate the genetic and clonal relationship shared by Australian Salmonella Sofia isolates. Methods and Results: A total of 84 Australian Salm. Sofia isolates from various states in Australia were typed using pulsed‐field gel electrophoresis (PFGE) (XbaI and SpeI) and repetitive element PCR (REP1R‐I primer). The previous problem of DNA degradation of Salm. Sofia strains was solved by modifying the lysis solution used to treat the bacterial plugs, allowing Salm. Sofia to be subtyped using PFGE. Molecular typing of isolates resulted in the generation of eight XbaI, six SpeI and five REP1 pattern profiles. Individual typing methods showed low discrimination index values (<0·5), indicating the poor discriminatory ability of the methods. However, the combination of the typing methods was able to improve the discrimination of isolates, further dividing them into 16 subtypes and raising the index value to 0·721. Conclusions: The combination of typing methods was shown to be the best approach to fingerprint Salm. Sofia. The Australian Salm. Sofia isolates only showed limited genetic diversity and probably share a clonal relationship. A majority of the Salm. Sofia isolates were not geographically restricted with the predominant pattern subtype observed amongst the isolates from various states. Significance and Impact of the Study: We have successfully devised a PFGE protocol that counteracts DNase activity of Salm. Sofia, enabling typing of this serovar.