Photosynthetic efficiency and nitrogen distribution under different nitrogen management and relationship with physiological N-use efficiency in three rice genotypes

Nitrogen fertilization strategies were widely adopted to enhance grain production and improve nitrogen utilization in rice all over the world. For fertilization timing strategy, ear fertilization was usually employed in recent years. For fertilization amount strategy, nitrogen fertilization would continually increase to meet the demands of increasing people for food. However, under heavy ear fertilization as well as great nitrogen amount (NA), physiological N-use efficiency (PE, defined as grain production per unit nitrogen uptake by plants) decreased. Under three NA and two ratios of fertilization given during ear development period to total NA (ear fertilization distribution ratio, EFDR), net photosynthetic rate (Pn), Pn to nitrogen content per unit area (photosynthetic N-use efficiency, Pn/N), nitrogen accumulation in plant tissues and PE of three rice (Oryza sativaL.) genotypes, Jinyou 253, Liangyoupeijiu and Baguixiang were screened in the first and second seasons in 2002 so as to understand the fluctuation patterns of Pn/N and nitrogen distribution in leaf blades under great NA & EFDR and relationship with PE in rice. Results showed that under greater NA & EFDR, Pn in flag leaves at heading and plant nitrogen accumulation at maturity always increased and PE & Pn/N always decreased in spite of increased grain production. Rice distributed more nitrogen in leaf blade under greater NA and EFDR. PE indicated significantly (P<0.05) positive relationship with Pn/N and negative relationship with nitrogen distribution ratio in leaf blades at heading and maturity, and no association with Pn in two growing seasons. Results suggested that low PE in rice under great NA and heavy ear fertilization is associated to more nitrogen distribution in leaf blades and decreases in photosynthetic efficiency.     

江苏沿海滩涂中华补血草的保护性研究

中华补血草是一种经济价值、生态价值较高的盐生植物,花朵细小艳丽,全草含各种黄酮体和杨梅树皮甙等有效成份,不仅可供观赏,还可药用.中华补血草可改善盐碱土的土壤结构,使盐土脱盐,被誉为盐碱地改造的"先锋植物".由于沿海滩涂开发速度加快,中华补血草的适生环境受到极大的威胁,导致种群数量越来越少.因此,加强对中华补血草的研究与迁地保护,势在必行.     

Characterization and crystallization of human DPY-30-like protein, an essential component of dosage compensation complex

Human DPY-30-like is a homolog of C. elegans DPY-30. DPY-30 is an essential component of dosage compensation machinery and loss of dpy-30 activity results in XX-specific lethality. In XO animals, DPY-30 is required for developmental processes other than dosage compensation. In yeast, the homolog of DPY-30, Saf19p, functions as a member of histone 3 lysine 4 methylation complex, which is the key part of epigenetic developmental control. In this report, human DPY-30-like protein was overexpressed and purified with the goal of structure determination. It was crystallized at 291 K in hanging drops by the vapour diffusion technique from a precipitant solution consisting of (NH4)2SO4 (1.5-2.0 M), Tris-HCl (0.1 M, pH 8.0). The crystal diffracted to 2.7 A resolution at 100 K in-house and belongs to the space group P4(1)2(1)2 or P4(3)2(1)2 with unit-cell parameters of a=b=74.5 A, c=87.0 A, alpha=beta=gamma=90.0 degrees. The asymmetric unit contains two molecules with 49% solvent content. We also analyzed its biochemical and biophysical characterizations. Efforts are now under way to determine the molecular structure of the DPY-30-like. These studies will open a new avenue towards the structure-based functional analysis of human DPY-30-like and dosage compensation machinery.     

中华须鳗嗅觉器官形态学观察

利用光学显微镜和扫描电镜观察了10尾不同体长中华须鳗嗅觉器官的结构.结果表明:中华须鳗嗅囊呈楔型;嗅囊膜和嗅囊腹面的透明膜共同围成嗅囊腔;嗅囊长径与眼径的平均比值为2.2倍;每侧嗅囊嗅板数变化范围在30～44之间;嗅板远轴端有一纤毛和嗅孔密集的舌状游离突;嗅板上皮纤毛密集,纤毛细胞表现为3种类型:纤毛感觉细胞、纤毛非感觉细胞和微绒毛感觉细胞;纤毛非感觉细胞和微绒毛细胞也出现在嗅囊壁.嗅板上大量的纤毛表明,中华须鳗嗅囊的水动力机制应属嗅板纤毛搅动型(isosmates).除观察到嗅囊壁表面有两种类型的微嵴外,还首次在嗅板上观察到一种呈荸荠状的杆状细胞.     

Investigating mechanisms of collagen thermal denaturation by high resolution second-harmonic generation imaging

We apply the technique of second-harmonic generation (SHG) microscopy to obtain large area submicron resolution image of Type I collagen from rat tail tendon as it is heated from 40 degrees C to 70 degrees C for 0-180 min. The change in the collagen structure as reflected in its SHG image is observed at length scales from submicron to hundreds of microns. We observed that heating the tendon below the temperature of 54 degrees C does not produce any change in the averaged SHG intensity. At the heating temperature of 54 degrees C and above, we find that increasing the heating temperature and time leads to decreasing SHG intensity. As the tendon is heated above 54 degrees C, the regions where the SHG signal vanish and form a tiger-tail like pattern. In addition, a decrease in the SHG signal occurs uniformly throughout the tendon. By comparing the relative SHG intensities in small and large areas, we found that the denaturation process responsible for forming the tiger-tail like pattern occurs at a higher rate than the global denaturation process occurring throughout the tendon. We also measured the fibril spacing and found that it remains constant at 1.61 +/- 0.04 micron for all heating temperature and times. The constant fibril density shows that the global denaturation process occurs at a length scale smaller than the size of the fibril. Our results show that second-harmonic generation microscopy is effective in monitoring the thermal damage to collagen and has potential applications in biomedicine.     

Microbial diversity in water and sediment of Lake Chaka, an athalassohaline lake in northwestern China

We employed culture-dependent and -independent techniques to study microbial diversity in Lake Chaka, a unique hypersaline lake (32.5% salinity) in northwest China. It is situated at 3,214 m above sea level in a dry climate. The average water depth is 2 to 3 cm. Halophilic isolates were obtained from the lake water, and halotolerant isolates were obtained from the shallow sediment. The isolates exhibited resistance to UV and gamma radiation. Microbial abundance in the sediments ranged from 10(8) cells/g at the water-sediment interface to 10(7) cells/g at a sediment depth of 42 cm. A major change in the bacterial community composition was observed across the interface. In the lake water, clone sequences affiliated with the Bacteroidetes were the most abundant, whereas in the sediments, sequences related to low G+C gram-positive bacteria were predominant. A similar change was also present in the archaeal community. While all archaeal clone sequences in the lake water belonged to the Halobacteriales, the majority of the sequences in the sediments were related to those previously obtained from methanogenic soils and sediments. The observed changes in the microbial community structure across the water-sediment interface were correlated with a decrease in salinity from the lake water (32.5%) to the sediments (approximately 4%). Across the interface, the redox state also changed from oxic to anoxic and may also have contributed to the observed shift in the microbial community.     

KNOCKDOWN OF THE IONOTROPIC γ‐AMINOBUTYRIC ACID RECEPTOR (GABAR) RDL GENE DECREASES FIPRONIL SUSCEPTIBILITY OF THE SMALL BROWN PLANTHOPPER,Laodelphax striatellus (HEMIPTERA: DELPHACIDAE)

Insect γ‐aminobutyric acid receptors (GABARs) are important molecular targets of cyclodiene and phenylpyrazole insecticides. Previously GABARs encoding rdl (resistant to dieldrin) genes responsible for dieldrin and fipronil resistance were identified in various economically important insect pests. In this study, we cloned the open reading frame cDNA sequence of rdl gene from fipronil‐susceptible and fipronil‐resistant strains of Laodelphax striatellus (Lsrdl). Sequence analysis confirmed the presence of a previously identified resistance‐conferring mutation. Different alternative splicing variants of Lsrdl were noted. Injection of dsLsrdl reduced the mRNA abundance of Lsrdl by 27–82%, and greatly decreased fipronil‐induced mortality of individuals from both susceptible and resistant strains. These data indicate that Lsrdl encodes a functional RDL subunit that mediates susceptibility to fipronil. Additionally, temporal and spatial expression analysis showed that Lsrdl was expressed at higher levels in eggs, fifth‐instar nymphs, and female adults than in third‐instar and fourth‐instar nymphs. Lsrdl was predominantly expressed in the heads of 2‐day‐old female adults. All these results provide useful background knowledge for better understanding of fipronil resistance related ionotropic GABA receptor rdl gene expressed variants and potential functional differences in insects.     

Human Organoids as a Promising Platform for Fighting COVID-19

The coronavirus disease 2019 (COVID-19) global pandemic evoked by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has triggered a major public health problem with significant morbidity and mortality. Understanding the pathogenesis and molecular mechanisms underlying this novel virus is crucial for both fundamental research and clinical trials in order to devise effective therapies and vaccination regimens. Basic research on SARS-CoV-2 largely depends on ex vivo models that allow viral invasion and replication. Organoid models are now emerging as a valuable tool to investigate viral biology and disease progression, serving as an efficient platform to investigate potential therapies for COVID-19. Here, we summarize various human stem cell-derived organoid types employed in SARS-CoV-2 studies. We highlight key findings from these models, including cell tropisms and molecular mechanisms in viral infection. We also describe their use in identifying potential therapeutic agents against SARS-CoV-2. As more and more advanced organoids emerge, they will facilitate the understanding of disease pathogenesis for drug development in this dreaded pandemic.