Loss of function of OsDCL1 affects microRNA accumulation and causes developmental defects in rice

MicroRNAs (miRNAs) and small interfering RNAs (siRNAs) are two types of noncoding RNAs involved in developmental regulation, genome maintenance, and defense in eukaryotes. The activity of Dicer or Dicer-like (DCL) proteins is required for the maturation of miRNAs and siRNAs. In this study, we cloned and sequenced 66 candidate rice (Oryza sativa) miRNAs out of 1,650 small RNA sequences (19 to approximately 25 nt), and they could be further grouped into 21 families, 12 of which are newly identified and three of which, OsmiR528, OsmiR529, and OsmiR530, have been confirmed by northern blot. To study the function of rice DCL proteins (OsDCLs) in the biogenesis of miRNAs and siRNAs, we searched genome databases and identified four OsDCLs. An RNA interference approach was applied to knock down two OsDCLs, OsDCL1 and OsDCL4, respectively. Strong loss of function of OsDCL1IR transformants that expressed inverted repeats of OsDCL1 resulted in developmental arrest at the seedling stage, and weak loss of function of OsDCL1IR transformants caused pleiotropic developmental defects. Moreover, all miRNAs tested were greatly reduced in OsDCL1IR but not OsDCL4IR transformants, indicating that OsDCL1 plays a critical role in miRNA processing in rice. In contrast, the production of siRNA from transgenic inverted repeats and endogenous CentO regions were not affected in either OsDCL1IR or OsDCL4IR transformants, suggesting that the production of miRNAs and siRNAs is via distinct OsDCLs.     

广东金山温泉沉积物中原核与真核微生物多样性初步分析

[目的]本研究旨在采用不同的PCR引物对广东省恩平市金山温泉的高温水底沉积物微生物多样性进行初步的分析.[方法]采用改进的玻璃珠法抽提温泉沉积物中环境基因组DNA,通过对用4对引物分别扩增得到的原核微生物16S rRNA基因和真核微生物ITS序列的分析,将所得到的数据与国际基因数据库GenBank进行相似性比较并构建系统发育树.[结果]研究发现原核类群G的 14个优势克隆中7个都属于蛭弧菌属(Bdellovibrio).与它们最相似的序列是从海洋中分离到的两个菌株 Bacteriovorax sp. NE1 (EF092445)和Bdellovibrio sp. JS5 (AF084859),相似性分别为96%和99%.原核类群X的4个序列主要属于蓝细菌类群,其中JS-X2与在美国黄石公园温泉发现的Uncultured Cyanobacterium (L35331)有95%的相似性,并且与已经全基因组测序的嗜热蓝细菌聚球藻Thermosynechococcus elongatus BP-1 (47118315)有89%的相似性.真核类群Z有三个类群,分别是Penicillium sp.,Lodderomyces sp.和Gloeotinia sp..其中大部分序列与青霉属相似性在88%～ 90%之间.[结论]所得到的结果显示金山温泉中的微生物多样性十分丰富.     

Studies on the Free Amino Acid Content in Anthers of Malesterile and Fertile Plants of Taigu Wheat,with Special Reference to Free Proline Content

Biochemical analyses were made on anthers and pistils at various developmental stages of both male-sterne and fertile plants of Taigu wheat. Analyses ineluded total free amino aeids and free proline. The following results were obtained: 1. There was no significant difference between the content of free proline in anthers of male-sterile and fertile plants at reduction division of mierospore mother cells. 2. In anthers with early uninucleate miorospores, the content of free proline of fertile plants was remarkably higher than that of male-sterile plants. It is interesting to note that at this stage the content of free proline in fertile plants rose to 1.65% of the dry weight of the anther, constituting 50% of the total free amino acids, and amounted to 7-fold of that in male-sterile plants. This result is in line with the results obtained with most cytoplasmic malesterile plants reported by other workers, although malesterility in Taigu wheat is controlled by the nueleus. 3. In pistils, at the stages eorresponding to the early uninneleate and the binueleate stages of the pollen, the free proline content of fertile plants was twice as much as that of the male-sterile plants. This differenee disappeared gradually after fertilization. 4. Tile content of total free amino aoids did not fluetuate as much as the free proline content. There was no differenee in anthers of both types of plants during reduction division of mierospore mother cells. In anthers with early uninueleate pollen grains, total free amino acid content of fertile plants exceeded that of male-sterile plant, the difference levelled off at latter stages. In pistils, before fertilization, the content of total free amino acids of the fertile phmts was slightly higher than that of the male-sterile plants. After fertilization t}fis difference was no nmre noticeable.     

The enzymes of a marine bacterial isolate from the brown alga <Emphasis Type="Italic">Sargassum polycystum</Emphasis> agardh, 1821, that catalyzes the transformation of polyanionic oligo-and polysaccharides

A search for enzymes involved in the degradation of polyanionic polysaccharides (fucoidans and alginic acid) was conducted among bacterial epiphytes of the brown alga Sargassum polycystum that grows in the territorial waters of the Socialist Republic of Vietnam. Two resistant bacterial strains, F10 and F14, have been isolated from the algal microflora that degrade the thallus of the alga under laboratory conditions. These bacterial strains differed in the morphological, physiological, and biochemical characteristics and in the composition of enzymes. The strains were studied for the ability to synthesize intracellular oligo-and polysaccharide hydrolases and alginate lyases. The optimal conditions for the growth of bacterial strain F14 and the biosynthesis of fucoidanase and polymannuronate-specific alginate lyase were determined. The partially purified alginate lyase was stable at a temperature up to 40°C and had an optimal pH 6.0 and an optimal temperature 35°C.     

Stable Li Metal Anode Enabled by Space Confinement and Uniform Curvature through Lithiophilic Nanotube Arrays

The application of lithium (Li) metal anodes in rechargeable batteries is primarily restricted by Li dendrite growth on the metal's surface, which leads to shortened cycle life and safety concerns. Herein, well‐spaced nanotubes with ultrauniform surface curvature are introduced as a Li metal anode structure. The ultrauniform nanotubular surface generates uniform local electric fields that evenly attract Li‐ions to the surface, thereby inducing even current density distribution. Moreover, the well‐defined nanotube spacing offers Li diffusion pathways to the electroactive areas as well as the confined spaces to host deposited Li. These structural attributes create a unique electrodeposition manner; i.e., Li metal homogenously deposits on the nanotubular wall, causing each Li nanotube to grow in circumference without obvious sign of dendritic formation. Thus, the full‐cell battery with the spaced Li nanotubes exhibits a high specific capacity of 132 mA h g^?1 at 1 C and an excellent coulombic efficiency of ≈99.85% over 400 cycles.     

BcMF9, a novel polygalacturonase gene, is required for both Brassica campestris intine and exine formation

Background and Aims

The polygalacturonase (PG) gene family has been found to be enriched in pollen of several species; however, little is currently known about the function of the PG gene in pollen development. To investigate the exact role that the PG gene has played in pollen development and about this family in general, one putative PG gene, Brassica campestris Male Fertility 9 (BcMF9), was isolated from Chinese cabbage (Brassica campestris ssp. chinensis, syn. B. rapa ssp. chinensis) and characterized.

Methods

RT-PCR, northern blotting and in situ hybridization were used to analyse the expression pattern of BcMF9, and antisense RNA technology was applied to study the function of this gene.

Key Results

BcMF9 is expressed in particular in the tapetum and microspore during the late stages of pollen development. Antisense RNA transgenic plants that displayed decreased expression of BcMF9 showed pollen morphological defects that resulted in reduced pollen germination efficiency. Transmission electron microscopy revealed that the homogeneous pectic exintine layer of pollen facing the exterior was over-developed and predominantly occupied the intine, reversing the normal proportional distribution of the internal endintine layer and the external exintine in transgenic pollen. Inhibition of BcMF9 also resulted in break-up of the previously formed tectum and baculae from the beginning of the binucleate stage, as a result of premature degradation of tapetum.

Conclusions

Several lines of evidence, including patterns of BcMF9 expression and phenotypic defects, suggest a sporophytic role in exine patterning, and a gametophytic mode of action of BcMF9 in intine formation. BcMF9 might act as a co-ordinator in the late stages of tapetum degeneration, and subsequently in the regulation of wall material secretion and, in turn, exine formation. BcMF9 might also play a role in intine formation, possibly via regulation of the dynamic metabolism of pectin.Key words: Brassica campestris, Chinese cabbage, exine, intine, PG, pollen wall, polygalacturonase, BcMF9     

Characteristic chemical probing patterns of loop motifs improve prediction accuracy of RNA secondary structures

RNA structures play a fundamental role in nearly every aspect of cellular physiology and pathology. Gaining insights into the functions of RNA molecules requires accurate predictions of RNA secondary structures. However, the existing thermodynamic folding models remain less accurate than desired, even when chemical probing data, such as selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) reactivities, are used as restraints. Unlike most SHAPE-directed algorithms that only consider SHAPE restraints for base pairing, we extract two-dimensional structural features encoded in SHAPE data and establish robust relationships between characteristic SHAPE patterns and loop motifs of various types (hairpin, internal, and bulge) and lengths (2–11 nucleotides). Such characteristic SHAPE patterns are closely related to the sugar pucker conformations of loop residues. Based on these patterns, we propose a computational method, SHAPELoop, which refines the predicted results of the existing methods, thereby further improving their prediction accuracy. In addition, SHAPELoop can provide information about local or global structural rearrangements (including pseudoknots) and help researchers to easily test their hypothesized secondary structures.