Divergent evolution of oxidosqualene cyclases in plants

Triterpenes are one of the largest classes of plant metabolites and have important functions. A diverse array of triterpenoid skeletons are synthesized via the isoprenoid pathway by enzymatic cyclization of 2,3-oxidosqualene. The genomes of the lower plants Chlamydomonas reinhardtii and moss (Physcomitrella patens) contain just one oxidosqualene cyclase (OSC) gene (for sterol biosynthesis), whereas the genomes of higher plants contain nine to 16 OSC genes. Here we carry out functional analysis of rice OSCs and rigorous phylogenetic analysis of 96 OSCs from higher plants, including Arabidopsis thaliana, Oryza sativa, Sorghum bicolor and Brachypodium distachyon. The functional analysis identified an amino acid sequence for isoarborinol synthase (OsIAS) (encoded by Os11g35710/OsOSC11) in rice. Our phylogenetic analysis suggests that expansion of OSC members in higher plants has occurred mainly through tandem duplication followed by positive selection and diversifying evolution, and consolidated the previous suggestion that dicot triterpene synthases have been derived from an ancestral lanosterol synthase instead of directly from their cycloartenol synthases. The phylogenetic trees are consistent with the reaction mechanisms of the protosteryl and dammarenyl cations which parent a wide variety of triterpene skeletal types, allowing us to predict the functions of the uncharacterized OSCs.     

Variation in grain arsenic assessed in a diverse panel of rice (Oryza sativa) grown in multiple sites

? Inorganic arsenic (As(i) ) in rice (Oryza sativa) grains is a possible threat to human health, with risk being strongly linked to total dietary rice consumption and consumed rice As(i) content. This study aimed to identify the range and stability of genetic variation in grain arsenic (As) in rice. ? Six field trials were conducted (one each in Bangladesh and China, two in Arkansas, USA over 2 yr, and two in Texas, USA comparing flooded and nonflood treatments) on a large number of common rice cultivars (c. 300) representing genetic diversity among international rice cultivars. ? Within each field there was a 3-34 fold range in grain As concentration which varied between rice subpopulations. Importantly, As(i) correlated strongly with total As among a subset of 40 cultivars harvested in Bangladesh and China. ? Genetic variation at all field sites was a large determining factor for grain As concentration, indicating that cultivars low in grain As could be developed through breeding. The temperate japonicas exhibited lower grain As compared with other subpopulations. Effects for year, location and flooding management were also statistically significant, suggesting that breeding strategies must take into account environmental factors.     

Simulated microgravity affects semicarbazide-sensitive amine oxidase expression in recombinant Escherichia coli by HPLC-ESI-QQQ analysis

Simulated microgravity has been reported to affect the gene, protein expression, and its function in the cells. Semicarbazide-sensitive amine oxidase (SSAO; E.C.1.4.3.6.) is widely distributed in vascular cells, smooth muscle cells, and adipocytes. It is noteworthy whether the expression of SSAO is affected under simulated microgravity or not. In this study, an SSAO-transformed Escherichia coli BL21 was constructed firstly. Then, a sensitive, selective, and accurate method based on high-performance liquid chromatography electrospray ionization triple quadrupole (HPLC-ESI-QQQ) was developed to determine the amount of SSAO in the E. coli BL21. The limit of detection and limit of quantification were 5.0 and 10 fmol, respectively. Finally, SSAO expression in the recombinant E. coli BL21 was evaluated with various gravity and temperature conditions by HPLC-ESI-QQQ analysis. It is interesting that the tendency in the alteration of SSAO under simulated microgravity showed temperature difference. At 18 °C, the amount of SSAO in the inclusion bodies and soluble fractions under the simulated microgravity increased by 83% and 116%, respectively, compared with normal gravity. However, the decrease by 38% and 49% in the inclusion bodies and soluble fractions under the simulated microgravity was observed at 37 °C. Results obtained here indicate that the SSAO expression under simulated microgravity is dramatically sensitive to the temperature. On the other hand, a novel bioreactor from this study may also be useful for the recombinant protein expression in the field of gene engineering.     

Cotton shoot plays a major role in mediating senescence induced by potassium deficiency

The objective of this study was to determine the roles of shoot and root in the regulation of premature leaf senescence induced by potassium (K) deficiency in cotton (Gossypium hirsutum L.). Two contrasting cultivars (CCRI41, more sensitive to K deficiency; and SCRC22, a less sensitive cultivar) were selected for self- and reciprocal-grafting, using standard grafting (one scion/one rootstock), Y grafting (two scions/one rootstock) and inverted Y grafting (one scion/two rootstocks) at the seedling stage. Standard grafting was studied in the field in 2007 and 2008. There were no obvious differences in senescence between CCRI41 and SCRC22 scions while supplied with sufficient K. However, SCRC22 scions showed significantly greater K content, SPAD values (chlorophyll content), soluble protein content and net photosynthetic rates than CCRI41 scions while grown in K deficient solution or soil, regardless of rootstock cultivars, grafting types, growth stage and growth conditions. Also, SCRC22 scions had greater yield and less variation in boll weight either between upper- and lower sympodials, or between proximal and distal fruit positions from the main stem in the field under K deficiency, probably owing to reduced leaf senescence. Although the effect of rootstocks on leaf senescence under K deficiency was significant in some cases, the scion cultivars explained the highest percentage of variations within grafting treatments. The shoot-to-root feedback signal(s), rather than high shoot demand for K nutrition, was involved in the shoot regulation of premature senescence in cotton plants, achieved possibly by altering root K uptake.     

Wnt1/βcatenin injury response activates the epicardium and cardiac fibroblasts to promote cardiac repair

Wnts are required for cardiogenesis but the role of specific Wnts in cardiac repair remains unknown. In this report, we show that a dynamic Wnt1/βcatenin injury response activates the epicardium and cardiac fibroblasts to promote cardiac repair. Acute ischaemic cardiac injury upregulates Wnt1 that is initially expressed in the epicardium and subsequently by cardiac fibroblasts in the region of injury. Following cardiac injury, the epicardium is activated organ-wide in a Wnt-dependent manner, expands, undergoes epithelial-mesenchymal transition (EMT) to generate cardiac fibroblasts, which localize in the subepicardial space. The injured regions in the heart are Wnt responsive as well and Wnt1 induces cardiac fibroblasts to proliferate and express pro-fibrotic genes. Disruption of downstream Wnt signalling in epicardial cells decreases epicardial expansion, EMT and leads to impaired cardiac function and ventricular dilatation after cardiac injury. Furthermore, disruption of Wnt/βcatenin signalling in cardiac fibroblasts impairs wound healing and decreases cardiac performance as well. These findings reveal that a pro-fibrotic Wnt1/βcatenin injury response is critically required for preserving cardiac function after acute ischaemic cardiac injury.     

The genome in space and time: Does form always follow function?

Recent systematic studies using newly developed genomic approaches have revealed common mechanisms and principles that underpin the spatial organization of eukaryotic genomes and allow them to respond and adapt to diverse functional demands. Genomes harbor, interpret, and propagate genetic and epigenetic information, and the three-dimensional (3D) organization of genomes in the nucleus should be intrinsically linked to their biological functions. However, our understanding of the mechanisms underlying both the topological organization of genomes and the various nuclear processes is still largely incomplete. In this essay, we focus on the functional relevance as well as the biophysical properties of common organizational themes in genomes (e.g. looping, clustering, compartmentalization, and dynamics), and examine the interconnection between genome structure and function from this angle. Present evidence supports the idea that, in general, genome architecture reflects and influences genome function, and is relatively stable. However, the answer as to whether genome architecture is a hallmark of cell identity remains elusive.     

Population genetics of wild Hizikia fusiformis (Sargassaceae, Phaeophyta) along China’s coast

Hizikia fusiformis is one of the important commercially cultivated seaweeds in China. Inter-simple sequence repeats (ISSR) and sequence-related amplified polymorphism (SRAP) markers were used to assess genetic structure of nine wild H. fusiformis populations collected along the coast of China. Of the 255 bands generated by 21 ISSR primers, 99.61% were polymorphic and 99.71% of 344 bands amplified by 30 SRAP primers were polymorphic. The tested high genetic diversities show that the average Nei’s genetic diversity (H) were 0.1519 and 0.1624, and average Shannon’s information index (I) were 0.2248 and 0.2400 in ISSR and SRAP analyses, respectively. Unweighted pair group method with arithmetic mean (UPGMA) dendrograms of the nine populations were divided into two main groups. The ISSR and SRAP analyses values of gene differentiation (G _ST, 0.5955, 0.5486, respectively) indicate that high variation exists among the nine populations, likely due to external interferences and limitation of gene flow (N _m?=?0.3397, 0.4114). Our study indicated that human activities and herbivore overgrazing had influenced the natural Hizikia populations and that the understanding of population genetics would be helpful in sustainable utilization and biomass conservation of Sargassaceae resources.     

Morphological and molecular characterization of free-floating and attached green macroalgae Ulva spp. in the Yellow Sea of China

During the summer of 2008 and 2009, massive algal blooms repeatedly broke out in the Yellow Sea of China. These were undoubtedly caused by the accumulations of one or more species in the macroalgal genus Ulva. In previous reports, morphological observation indicated that the species involved in this phenomenon is Ulva prolifera but molecular analyses indicated that the species belongs to an Ulva linza–procera–prolifera (LPP) clade. Correct identification of the bloom species is required to understand and manage the blooms, but the taxonomic status of the bloom species remains unclear. In the current study, the taxonomic status of 22 selected specimens from the Yellow Sea was assessed by using both morphological and molecular (ITS and rbcL sequences) data. In addition, 5S rDNA analyses were performed for those samples clustering in the LPP clade, and phylogenetic tree and ribotype analyses were constructed for determining the possible origin of the bloom. Three free-floating and two attached Ulva species were distinguished and described: Ulva compressa Linnaeus and Ulva pertusa Kjellman were found in free-floating samples; U. linza Linnaeus was found on rocks; and U. prolifera O.F. Müller was found in both habitats. Diversity in free-floating Ulva of the Yellow Sea appears to be greater than previously thought. The dominant free-floating Ulva species, U. prolifera, was not closely related to local populations attached to rocks but was closely related to populations from Japan.     

Study on the destructive effect to inherent quality of Fritillaria thunbergii Miq. (Zhebeimu) by sulfur-fumigated process using chromatographic fingerprinting analysis

The after-harvesting sun-dried processing of Fritillariae thunbergii bulbus (Zhebeimu) was the traditional treatment for commodity. Over recent decades the natural drying process for bulbus of Fritillariae has been replaced by sulfur-fumigation for reducing the drying duration and pest control. We used ultra-performance liquid chromatography coupled with evaporative light scattering detection (UPLC-ELSD) fingerprinting analysis and major alkaloids determination to investigate the potential damaging effect of the sulfur-fumigating process. The experimental conditions were as follows: Chromatography was proceeded on Waters Acquity UPLC BEH C(18) column; the linear gradient elution was conducted with mobile phase prepared from acetonitrile-0.02% triethylamine; the drift tube temperature was set at 40°C with a nitrogen flow-rate of 30psi, and the spray parameter was set 40%. All calibration curves showed good linear regression (R>0.9991) within the tested range. The method was validated for precision, accuracy, limit of detection and quantification. The study also has shown that sulfur-fumigated samples had significant loss of the main active compounds and a more destructive fingerprint profile when compared to the sun-dried samples.