Simulated Yeast with Mobile Polarity Sites Is More Sensitive to Pheromone Gradients

Cell polarity is the asymmetric distribution of cellular components and molecules. It is crucially important for effective cell motility and other directional functions. However, practically all types of cells were exposed in a large amount of molecular noise which interfered cell polarity, leading the cells to polarize in the wrong direction. Interestingly, though exposed in molecular noise, yeast cells can usually find and polarize in the direction of extracellular pheromone gradients during mating. This study investigated how yeast cells decoded the extracellular pheromone gradient to polarize in the right direction despite the noise. With particle-based simulations, we found that when exposed to a shallow signal gradient, the simulated yeast with mobile polarity sites interpreted the direction of the signal more accurately than the one with static polarity sites. Therefore, the highly dynamic polarity sites could help yeast cells to decode the extracellular pheromone gradient against molecular noise. Future studies will focus on adding more complex signaling pathways to the simulated yeast models to further investigate the effect of mobile polarity sites on yeast polarity establishment.Bachelor of Scienc

The Responses of the Quantitative Characteristics of a Ramet Population of the Ephemeroid Rhizomatous Sedge Carex physodes

In this study, the soil moisture content was measured, and the quantitative characteristics of this sedge species were compared. The phenotypic plasticity of each parameter and the linear regression relationships were analyzed. The results showed that the soil moisture content was significantly affected by location, soil depth, and sampling date. The aboveground biomass, underground biomass, biomass density, and population density at the peak were significantly higher than elsewhere on the dune. However, the morphological plasticity index of the quantitative characteristics was higher at the base and middle of the dune. When the soil moisture content decreased, the underground biomass and ramet biomass density increased. The aboveground and underground biomasses were strongly negatively correlated, but the ramet height and aboveground biomass were strongly positively correlated. These results indicated that the soil water content significantly affected the clonal growth of C. physodes. The responsiveness of C. physodes may be adaptive when the soil resource supply is low. The strong morphological plasticity of the species appears to be ecologically important for the maintenance and dominance of this species in the dune habitat

Isolation and Characterization of Microsatellite Loci for Hibiscus aridicola (Malvaceae), an Endangered Plant Endemic to the Dry-Hot Valleys of Jinsha River in Southwest China

Hibiscus aridicola (Malvaceae) is an endangered ornamental shrub endemic to the dry-hot valleys of Jinsha River in southwest China. Only four natural populations of H. aridicola exist in the wild according to our field investigation. It can be inferred that H. aridicola is facing a very high risk of extinction in the wild and an urgent conservation strategy is required. By using a modified biotin-streptavidin capture method, a total of 40 microsatellite markers were developed and characterized in H. aridicola for the first time. Polymorphisms were evaluated in 39 individuals from four natural populations. Fifteen of the markers showed polymorphisms with two to six alleles per locus; the observed heterozygosity ranged from 0.19 to 0.72. These microsatellite loci would be useful tools for population genetics studies on H. aridicola and other con-generic species which are important to the conservation and development of endangered species

Emended Circumscription of Begonia silletensis (Begoniaceae) and Description of a New Subspecies from Yunnan, China

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Particle-based simulations reveal two positive feedback loops allow relocation and stabilization of the polarity site during yeast mating.

Many cells adjust the direction of polarized growth or migration in response to external directional cues. The yeast Saccharomyces cerevisiae orient their cell fronts (also called polarity sites) up pheromone gradients in the course of mating. However, the initial polarity site is often not oriented towards the eventual mating partner, and cells relocate the polarity site in an indecisive manner before developing a stable orientation. During this reorientation phase, the polarity site displays erratic assembly-disassembly behavior and moves around the cell cortex. The mechanisms underlying this dynamic behavior remain poorly understood. Particle-based simulations of the core polarity circuit revealed that molecular-level fluctuations are unlikely to overcome the strong positive feedback required for polarization and generate relocating polarity sites. Surprisingly, inclusion of a second pathway that promotes polarity site orientation generated relocating polarity sites with properties similar to those observed experimentally. This pathway forms a second positive feedback loop involving the recruitment of receptors to the cell membrane and couples polarity establishment to gradient sensing. This second positive feedback loop also allows cells to stabilize their polarity site once the site is aligned with the pheromone gradient

Identity and distribution of weedy Pedicularis kansuensis Maxim. (Orobanchaceae) in Tianshan mountains of Xinjiang: morphological, anatomical and molecular evidence

Weedy plants affect the biodiversity and ecosystem function as well as the crop and fodder plant production. However, adequate management requires detailed knowledge of the taxonomic identity of these plants. Here, we focused on a hemiparasitic Pedicularis species (Orobanchaceae), which occurs at high densities and results in significant biomass reductions in forage grasses in Bayanbulak Grassland of Xinjiang. The identity of this target species is not clear, with conflicting reports in publications and in herbarium collections. Hence, clear and management-relevant information on demography and reproductive ecology is difficult to be obtained from the literature. Therefore, we analyzed field and archival materials collected from Xinjiang in order to clarify the identity and distribution of the target species. Morphological analyses suggested that the populations at Bayanbulak Grassland should be Pedicularis kansuensis Maxim. rather than P. verticillata L. which has been accepted in the available literature. Phylogenetic analysis with a combination of three barcodes (matK, rbcL and trnH-psbA) uniting a clade of P. kansuensis and individuals from Bayanbulak Grassland populations with 100% bootstrap support, confirmed the target species to be P. kansuensis. Anatomical investigations and field observations showed that the target species is an annual or biennial herb, which also fits with the life cycle as P. kansuensis. Based on archive material and field observations, we verified that the distribution of P. kansuensis is mainly concentrated in the Tianshan Mountains of Xinjiang

Characteristics and utilization of plant diversity and resources in Central Asia

The geographical region of Central Asia comprises Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, Turkmenistan, and the Xinjiang Uygur Autonomous Region of China. Central Asia’s temperate forests, steppes, and sandy deserts, including riparian tugai forests, have been identified by the World Wide Fund for Nature as Global 200 ecoregions, and the Mountains of Central Asia are considered biodiversity hotspots. Here, we describe and analyze the diverse characteristics and utilization of plant diversity and resources of the region. We confirm that there are 9520 species of higher plants, 20% of which are endemic species, belonging to 138 families and 1176 genera. The vegetation geography of Central Asia can be divided into 5 provinces and 33 districts, and more than 65% species have a Central Asian geographical distribution pattern. Plant resource utilization can be grouped into 5 categories and 31 subcategories, including food, medicine, industry, environmental protection, construction, and plant germplasm. In this review, we also discuss the principal threats to plant biodiversity in Central Asia posed by global climate change and offer recommendations for conservation strategies

N-P Fertilization Inhibits Growth of Root Hemiparasite Pedicularis kansuensis in Natural Grassland

Fertilization has been shown to affect interactions between root hemiparasitic plants and their host plants, alleviating damage to the hosts by parasitism. However, as a majority of studies were conducted in pot cultivation, the influence of fertilizer application on root hemiparasites and the surrounding plant community in field conditions as well as relevant mechanisms remain unclear. We manipulated soil nutrient resources in a semi-arid subalpine grassland in the Tianshan Mountains, northwestern China, to explore the links between fertilization and plant community composition, productivity, survival, and growth of a weedy root hemiparasite (Pedicularis kansuensis). Nitrogen (at a low rate, LN, 30 kg N ha-1 year-1 as urea; or at a high rate, HN, 90 kg N ha-1 year-1 as urea) and phosphorus [100 kg ha-1 year-1 as Ca(H2PO4)2⋅H2O] were added during two growing seasons. Patterns of foliar nutrient balances were described with isometric log ratios for the different plant functional groups receiving these fertilization regimes. Fertilization with LN, HN, and P reduced above-ground biomass of P. kansuensis, with above-ground biomass in the fertilization treatments, respectively, 12, 1, and 39% of the value found in the unfertilized control. Up to three times more above-ground biomass was produced in graminoids receiving fertilizers, whereas forb above-ground biomass was virtually unchanged by the fertilization regimes and forb species richness was reduced by 52% in the HN treatment. Fertilization altered foliar nutrient balances, and distinct patterns emerged for each plant functional group. Foliar [C | P,N] balance in the plant community was negatively correlated with above-ground biomass (P = 0.03). The inhibited competitiveness of P. kansuensis, which showed a much higher [C | P,N] balance, could be attributed to reduced C assimilation rather than mineral nutrient acquisition, as shown by significant increase in foliar N and P concentrations but little increase in C concentration following fertilization