A novel approach to the establishment of dual cultures of pearl millet and Sclerospora graminicola

Dual cultures were successfully established using malformed florets of pearl millet infected with Sclerospora graminicola, the downy mildew pathogen. A higher proportion (86%) of calli from malformed florets formed dual cultures on Murashige and Skoog's (MS) medium with 2 mg 1^-1 of 2,4-dichlorophenoxy acetic acid (2,4-d), compared to shoot tips (25%). Fungal mycelium covered the entire surface of the callus within 30 days of placement of explants on the MS medium with 2 mg 1^-1 of 2,4-d. The infected calli also differentiated and produced plantlets when transferred to MS medium without 2,4-d.     

Effect of exogenous plant growth regulators on in vitro seed growth,embryo development,and haploid production in a cross between H. vulgare (L.) and H. bulbosum (L.)

Exogenous plant growth regulators are known to increase the efficiency of interspecific and intergeneric crosses. In vitro floret culture provides a defined system for assessing the importance of various plant growth regulators on the determinants of haploid production efficiency (seed set, embryos per seeds, and plants per embryos) in Hordeum vulgare × Hordeum bulbosum crosses. The individual and combined effects of three plant growth regulators (2,4-D, GA₃ and kinetin) on in vitro seed growth, embryo development and haploid production efficiency were tested in floret culture of the cross H. vulgare, cultivar Klages × H. bulbosum. All treatments, except kinetin alone, produced larger seeds and more embryos/100 seeds than the control (no plant growth regulator). 2,4-D alone was superior to GA₃ alone in haploid production efficiency (70.6 vs. 51.5) as measured by the number of plants regenerated/100 florets pollinated. Although kinetin +2,4-D+GA₃ produced the largest seeds and embryos, no advantage over 2,4-D alone was observed in haploid production efficiency. 2,4-D alone or kinetin +2,4-D are recommended for the purpose of barley haploid production in floret culture using the bulbosum method.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid     

Anatomy and dendrochronological potential of Moringa peregrina from the hyper-arid desert in Egypt

The annual growth and wood characteristics of tree species at southern Mediterranean countries, and its relationship with climate variables are recently two important topics for the researchers in this region. Although Moringa peregrina (Forssk.) Fiori is a key species in Africa due to its medicinal and economic values (e.g. as fuel, food and water purifier), little is known about its annual growth or its response to climate variables. In this study, we analyze its dendrochronological potential, macroscopic and microscopic wood structure, and correlation with climate. Wood discs were collected from two desert sites in Egypt: Saint Catherine (SC) and Hurghada (HG). Wood discs and micro-slides were prepared, and the distinctness and pattern of rings, vessels, and ray structure were examined microscopically. The ring boundaries of M. peregrina were distinct and marked by thick-walled and flattened fibers. For the HG site, the resulting ring-width chronology spans 16 years, from 2001 to 2016. A significant positive relationship was found between tree growth at HG and precipitation prior to the vegetation period (January-March). April temperature of the year prior to growth had a significant positive relationship with M. peregrina growth. In contrast, April and May-August temperatures of the current growing season had a significant negative relationship with tree growth. We could not develop a chronology for M. peregrina at SC site due to the presence of growth anomalies in the collected wood discs from the site. Consequently, we did not get a clear picture on the climate- annual growth relationship for M. peregrina trees at this site. At SC, M. peregrina trees respond to stressful environmental conditions by adjusting their anatomical structure to produce a high number of small vessels. Moreover, there was spatial variability in the architecture of ray parenchyma that reflected the degree of stress in both sites. The results of this study improve our understanding of the growth-climate relationship in sub-tropical trees and the potential role of ray parenchyma in stressed environments.     

Penicamedine A,a Highly Oxygenated Hexacyclic Indole Alkaloid from Penicillium camemberti

A highly oxygenated hexacyclic indole alkaloid, penicamedine A ( 1 ), bearing a rare furan ring, was isolated from the culture broth of Penicillium camemberti, together with two known analogs, iso‐α‐cyclopiazonic acid ( 2 ) and cyclopiazonic acid ( 3 ). The structure of 1 was elucidated by comprehensive spectroscopic analyses including NMR and HR‐ESI‐MS. Its absolute configuration was further confirmed unambiguously by single‐crystal X‐ray diffraction analysis. Compound 1 was evaluated for anti‐HIV activity with p24 assays and tested for cytotoxic activities against five human cancer cell lines, including HL‐60, SMMC‐7721, A‐549, MCF‐7, SW480, and the immortalized non‐cancerous human pulmonary epithelial cell line BEAS‐2B by MTS method.     

Modeling biological invasions into periodically fragmented environments

Range expansion of a single species in a regularly striped environment is studied by using an extended Fisher model, in which the rates of diffusion and reproduction periodically fluctuate between favorable and unfavorable habitats. The model is analyzed for two initial conditions: the initial population density is concentrated on a straight line or at the origin. For each case, we derive a mathematical formula which characterizes the spatio-temporal pattern of range expansion. When initial distribution starts from a straight line, it evolves to a traveling periodic wave (TPW), whose frontal speed is analytically determinable. When the range starts from the origin, it tends to expand radially at a constant average speed in each direction (ray speed) keeping its frontal envelope in a similar shape. By examining the relation between the ray speed and the TPW speed, we derive the ray speed in a parametric form, from which the envelope of the expanding range can be predicted. Thus we analyze how the pattern and speed of the range expansion are affected by the pattern and scale of fragmentation, and the qualities of favorable and unfavorable habitats. The major results include: (1). The envelope of the expanding range show a variety of patterns, nearly circular, oval-like, spindle-like, depending on parameter values; (2). All these patterns are elongated in the direction of stripes; (3). When the scale of fragmentation is enlarged without changing the relative spatial pattern, the ray speed in any direction increases, i.e., the rate of range expansion increases.     

Immunohistochemical localization of agatharesinol,a heartwood norlignan,in Cryptomeria japonica

Localization of a heartwood norlignan, agatharesinol, in Sugi (Japanese cedar, Cryptomeria japonica D. Don, Taxodiaceae) was investigated by immunohistochemistry. Immuno light microscopy showed that the contents of ray parenchyma cells were immunostained in heartwood but not in sapwood. The staining of the heartwood tissue was competitively inhibited by agatharesinol but not by other Sugi heartwood extractives, and was, furthermore, markedly reduced by pre-extraction of the tissue with MeOH. These results indicated that the staining can be ascribed to the immunolabeling of agatharesinol in situ. The accumulations over the inner surface of some tracheid cell walls adjacent to the ray parenchyma cells were also immunolabeled, while the contents in axial parenchyma cells were not. In conclusion, agatharesinol was localized in the ray parenchyma cells in Sugi heartwood, and differences between the chemical structure of the contents of ray and axial parenchyma cells were also suggested.     

北京萤火虫复眼的模型小眼设计与光线追迹

以实际的北京萤火虫复眼结构与生理参数与依据,基于已知的ＧＲＩＮ透镜特征,把小眼的整个光学系统分成几个部分被模型化。模型中,在晶体柱部分使用了一个径向梯度折射率透镜柱具有的抛物线轮廓折射率公式;在晶锥末端所接的半椭球ＧＲＩＮ透镜部分,使用了一个径向梯度和纵向梯度分布都存在的折射率公式．模型的尺寸与折射率的大小根据实际晶锥的测量值．通过对模型小眼的光线追迹,证明模型小眼基本上是一个平行光入射,年行光出射的望远镜系统．小眼光学系统的前半部分把入射的平行光束聚焦到中间焦点,而这个点的位置恰好位于实际晶锥的腰的部位,而光线再次经过晶锥近端以后又以大致平行光束从晶锥末端出射。此模型小眼的最大入射角为３０度,在这个入射角内其角放大率基本上是相同的。随着对平行入射光束与小眼光轴的角度的增加,所产生的中间像越来越远离晶锥光轴。     

Molecular Evolution of Duplicated Ray Finned Fish HoxA Clusters: Increased Synonymous Substitution Rate and Asymmetrical Co-divergence of Coding and Non-coding Sequences

In this study the molecular evolution of duplicated HoxA genes in zebrafish and fugu has been investigated. All 18 duplicated HoxA genes studied have a higher non-synonymous substitution rate than the corresponding genes in either bichir or paddlefish, where these genes are not duplicated. The higher rate of evolution is not due solely to a higher non-synonymous-to-synonymous rate ratio but to an increase in both the non-synonymous as well as the synonymous substitution rate. The synonymous rate increase can be explained by a change in base composition, codon usage, or mutation rate. We found no changes in nucleotide composition or codon bias. Thus, we suggest that the HoxA genes may experience an increased mutation rate following cluster duplication. In the non-Hox nuclear gene RAG1 only an increase in non-synonymous substitutions could be detected, suggesting that the increased mutation rate is specific to duplicated Hox clusters and might be related to the structural instability of Hox clusters following duplication. The divergence among paralog genes tends to be asymmetric, with one paralog diverging faster than the other. In fugu, all b-paralogs diverge faster than the a-paralogs, while in zebrafish Hoxa-13a diverges faster. This asymmetry corresponds to the asymmetry in the divergence rate of conserved non-coding sequences, i.e., putative cis-regulatory elements. These results suggest that the 5′ HoxA genes in the same cluster belong to a co-evolutionary unit in which genes have a tendency to diverge together. Reviewing Editor: Dr. Axel Meyer     

Differential Response of Floret Opening in Male-Sterile and Male-Fertile Rices to Methy Jasmonate

Effects of methyl jasmonate (MeJA) on floret opening were investigated in male-sterile and male-fertile rice ( Oryza sativa subsp. indica ). Excised or intact panicles with several top florets flowered one day before the experiments were soaked in MeJA, salicylic acid (SA), 24-epibrassinolide (24-epiBL) or control solution for 2 min. MeJA at the concentration of 4 mmol/L significantly promoted rice floret opening; the response of floret opening of male-sterile rice to MeJA was more sensitive than that of male-fertile rice (such as maintenance line and conventional variety). The percentage of finally opened-floret per panicle of Zhenshan 97A (cytoplasmic male sterile line) or Pei'ai 64S (thermo-sensitive genic male sterile line) treated with MeJA was over 40% in the day of experiment, that of Zhenshan 97B (maintenance) and Pei'ai 64 (conventional variety) was (21±1.5)% and (25±2.1)%, respectively; floret opening of intact Pei'ai 64S panicles in the field could also be induced by 2-mmol/L MeJA. The percentage of opened floret in all control panicles was 0% or less than 5% in the day of experiment. The percentage of fertilized-grain of Zhenshan 97A and Longtepu A could be increased over 24% by spraying panicles with 2-mmol/L MeJA solution （circa 6.0 μmol per panicle）. The lag time (time from the finishing of treatment to first floret opening) of male sterile line responsing to MeJA was 10 min shorter than that of male fertile line. MeJA induction on the rice floret opening could markedly be inhibited by SA solution at the concentration of 1 mmol/L, and the inhibition of SA on MeJA induction on floret opening of male-sterile rice could be nullified by MeJA treatment again. MeJA effect on floret opening of male-sterile rice could be clearly synergized by pretreatment with 24-epibrassinolide (24-epiBL).