Characterization of embryo and protocorm development of Paphiopedilum spicerianum.

Paphiopedilum spicerianum (P. spicerianum) is a rare orchid species with high ornamental value. Asymbiotic germination is the most efficient propagation method for conservation and commercial purposes because clonal propagation is very difficult and the separation of native species of Paphiopedilum through aseptic seeding is uncommon owing to their conservatism. However, a high protocorm developmental arresting rate during the asymbiotic germination is the major obstacle for seedling establishment. The fundamental understanding of embryo and protocorm developmental mechanisms will guide the development of an effective propagation method. The morphological and physiological characterization of the key developmental process of embryos and protocorms shows that the mature seeds of P. spicerianum consist of a spherical embryo without an endosperm. Seed coats become heavily lignified once the embryo is mature. Embryo cell size is relatively uniform, and significant structure polarity and cell size gradients occur at the early protocorm stage. The high level of auxin and cytokinin accumulation at the early stage of embryo development and protocorm stage may help to facilitate cell division. The transcriptome profiles of protocorms at three different developmental stages were compared to explore the regulatory mechanism of protocorm development. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that differentially expressed genes were implicated in secondary metabolite metabolism, plant hormone signal transduction and photosynthesis. The temporal expression patterns of candidate genes related to embryo and shoot development were analyzed to reveal their roles in protocorm development: in the early stage of protocorm development, embryonic development related genes such as SERKs and BBM1 were active, while in the late stage of protocorm, shoot apical meristem related genes such as WOX8, CLAVATA2, CUC2, and SCR were active.

Seasonal Pattern of Nutrient Limitation in a Eutrophic Lake and Quantitative Analysis of the Impacts from Internal Nutrient Cycling.

Nutrient dynamics in lakes are determined by the external anthropogenic discharges and unobserved internal cycling processes. In this work, a decadal nutrient data set from the eutrophic Lake Taihu, China, revealed a strong seasonal pattern of nutrient concentration and limitation. A nutrient-driven dynamic eutrophication model based on a Bayesian hierarchical framework was established to quantify the relative contributions to temporal variations from external discharges and internal processes. Results showed that after years of efforts on nutrient reduction, external discharges were relatively small and fluctuated less between seasons compared to the internal processes. A quantitative relationship between monthly nutrient concentration and corresponding internal loading was observed. Lake sediment could transform from a source of phosphorus in overlying water in summer and autumn to a sink in winter and spring. Together with temporal variations in nitrification and denitrification, seasonal transformation from the limitation of phosphorus induced colimitation of nitrogen and phosphorus. Understanding the potential impact of internal nutrient cycling on a seasonal pattern of nutrient concentration and limitation, the growth of phytoplankton, and, possibly, phytoplankton community composition should be emphasized, given the change in the relative importance of external discharges and internal loading in the process of lake restoration.

Near-infrared carbon dots-based fluorescence turn on aptasensor for determination of carcinoembryonic antigen in pleural effusion.

Early detection of carcinoembryonic antigen (CEA) is of great significance for the screening, diagnosis, monitoring and prognosis analysis of lung cancer. Herein, a novel fluorescence aptasensor with high signal-noise ratio (SNR) was constructed to achieve highly-sensitive detection of CEA relied upon the fluorescence resonance energy transfer (FRET) between near-infrared carbon dots (NIR-CDs) and gold nanorods (AuNRs). Initially, AuNRs@SiO2-Aptamer and NIR-CDs-DNA probe were prepared via the covalent bonding reaction between their corresponding carboxyl and amino groups, respectively. After DNA hybridization, the aptasensor was formed, meanwhile, the fluorescence of NIR-CDs was quenched by AuNRs@SiO2. Once CEA encountered the aptasensor, it would selectively combine with CEA aptamer to unwind the preformed DNA double-strand architecture thereby resulting in the NIR-CDs-DNA detach from the surface of AuNRs@SiO2. The attendant fluorescence recovery of NIR-CDs was linearly correlated with the concentration of CEA. According to this relationship, the NIR-CDs based "turn on" sensing system was constructed and exhibited prominent responses toward CEA in the concentration range of 0.1-5000 pg/mL and a relatively low detection limit (0.02 pg/mL). Moreover, it displayed high specificity against other biomarkers or proteins, good reproducibility and acceptable accuracy regarding human pleural effusion samples.