Within‐field spatial distribution patterns of corn planthopper,Peregrinus maidis,and severity of hopperburn and Maize mosaic virus symptoms as influenced by sunn hemp intercropping

Habitat management (e.g., intercropping) may alter within‐field spatial distribution patterns of herbivores, from a typical pattern as observed in a monoculture, and may influence patterns of crop injury. Field trials were conducted to study the effect of intercropping maize, Zea mays L. (Poaceae), with sunn hemp, Crotalaria juncea L. (Fabaceae) strips on within‐field spatial distribution patterns of corn planthopper, Peregrinus maidis (Ashmead) (Hemiptera: Delphacidae), and combined severity of hopperburn and Maize mosaic virus (MMV) (Rhabdoviridae: Nucleorhabdovirus) symptoms. In each field trial, spatially explicit data on P. maidis counts and ratings of severity of symptoms were obtained by sampling maize plants at weekly intervals. These data were used to examine the spatial patterns of P. maidis and severity of symptoms in maize‐intercropped and monoculture plots with Spatial Analysis for Distance IndicEs (SADIE) methodology. Spatial aggregation patterns of P. maidis in each treatment plot were not consistent among the field trials and tended to be mediated by their population densities. Interpolation of local cluster indices showed that P. maidis were more often aggregated at the field edges, irrespective of treatment. At times of MMV incidence in field trials (fall 2010 and spring 2011), the patch clusters of P. maidis and symptomatic plants were located at the field edges, but were spatially unassociated in both treatment plots. The results provided an approximation of the unpredictability of P. maidis spatial patterns at different population densities and their association with severity of symptoms in two maize‐cropping systems. However, the gap clusters of symptomatic plants were primarily located at the field interiors and were larger in intercropped than in monoculture plots. Such spatial pattern of symptomatic plants resulted in the reduced incidence of MMV in the intercropped plot compared with the monoculture plot, suggesting intercropping sunn hemp can be a useful tool in the management of MMV in maize fields.     

Hold your breath beetle—Mites!

Respiratory gas exchange in insects occurs via a branching tracheal system. The entrances to the air‐filled tracheae are the spiracles, which are gate‐like structures in the exoskeleton. The open or closed state of spiracles defines the three possible gas exchange patterns of insects. In resting insects, spiracles may open and close over time in a repeatable fashion that results in a discontinuous gas exchange (DGE) pattern characterized by periods of zero organism‐to‐environment gas exchange. Several adaptive hypotheses have been proposed to explain why insects engage in DGE, but none have attracted overwhelming support. We provide support for a previously untested hypothesis that posits that DGE minimizes the risk of infestation of the tracheal system by mites and other agents. Here, we analyze the respiratory patterns of 15 species of ground beetle (Carabidae), of which more than 40% of individuals harbored external mites. Compared with mite‐free individuals, infested one's engaged significantly more often in DGE. Mite‐free individuals predominantly employed a cyclic or continuous gas exchange pattern, which did not include complete spiracle closure. Complete spiracle closure may prevent parasites from invading, clogging, or transferring pathogens to the tracheal system or from foraging on tissue not protected by thick chitinous layers.     

Elm leaves ‘warned’ by insect egg deposition reduce survival of hatching larvae by a shift in their quantitative leaf metabolite pattern

Plants may take insect eggs on their leaves as a warning of future herbivory and intensify their defence against feeding larvae. Responsible agents are, however, largely unknown, and little knowledge is available on this phenomenon in perennial plants. We investigated how egg deposition affects the anti‐herbivore defence of elm against the multivoltine elm leaf beetle. Prior egg deposition caused changes in the quality of feeding‐damaged leaves that resulted in increased larval mortality and reduced reproductive capacity of the herbivore by harming especially female larvae. Chemical analyses of primary and secondary leaf metabolites in feeding‐damaged, egg‐free (F) and feeding‐damaged, egg‐deposited (EF)‐leaves revealed only small differences in concentrations when comparing metabolites singly. However, a pattern‐focused analysis showed clearly separable patterns of (F) and (EF)‐leaves because of concentration differences in especially nitrogen and phenolics, of which robinin was consumed in greater amounts by larvae on (EF) than on (F)‐leaves. Our study shows that insect egg deposition mediates a shift in the quantitative nutritional pattern of feeding‐damaged leaves, and thus might limit the herbivore's population growth by reducing the number of especially female herbivores. This may be a strategy that pays off in a long run particularly in perennial plants against multivoltine herbivores.     

Four receptor‐like cytoplasmic kinases regulate development and immunity in rice

Receptor‐like cytoplasmic kinases (RLCKs) represent a large family of proteins in plants. However, few RLCKs have been well characterized. Here, we report the functional characterization of four rice RLCKs – OsRLCK57, OsRLCK107, OsRLCK118 and OsRLCK176 from subfamily VII. These OsRLCKs interact with the rice brassinosteroid receptor, OsBRI1 in yeast cell, but not the XA21 immune receptor. Transgenic lines silenced for each of these genes have enlarged leaf angles and are hypersensitive to brassinolide treatment compared to wild type rice. Transgenic plants silenced for OsRLCK57 had significantly fewer tillers and reduced panicle secondary branching, and lines silenced for OsRLCK107 and OsRLCK118 produce fewer seeds. Silencing of these genes decreased Xa21 gene expression and compromised XA21‐mediated immunity to Xanthomonas oryzae pv. oryzae. Our study demonstrates that these OsRLCKs negatively regulate BR signalling, while positively regulating immune responses by contributing to the expression of the immune receptor XA21.     

The low mitochondrial diversities in lizardfish Saurida elongate: Recent population expansion and selection

To investigate the phylogeographic pattern and historical demography of Saurida elongata, a 463 base pair fragment of the mitochondrial DNA control region was analyzed in 118 individuals collected from five populations in the East China Sea and South China Sea. The results revealed remarkably low nucleotide diversity in S. elongata, which was probably caused by selection during Pleistocene drastic climate fluctuations. Phylogenetic relationship was continuous, but a localized clade was found dominating Beihai population. Mismatch analyses showed that S. elongata experienced both demographic and range expansions. Among these populations, Beihai population expanded latest. Localization of haplotypes clade in Beihai was likely a result of the selection when new habitat was established during a range expansion, and indicated limited gene flow between Beihai and other populations. Our results suggested Beihai population should be managed separately in fishery.     

精子介导GFP基因在小鼠早期胚胎中的表达

利用 DIG 末端标记技术和免疫组化技术分析了小鼠精子体外结合内化外源DNA的效率。试验结果表明,不同小鼠个体的精子结合外源DNA的阳性率有明显差异（P<0.01）,平均为13%。利用考马斯亮蓝染色评价了小鼠精子顶体反应发生的情况,筛选出TYH培养液为较合适的体外受精液。利用小鼠体外受精技术,将体外转染GFP基因并获能的小鼠精子与成熟卵母细胞进行体外受精,受精卵进行体外培养,表达GFP胎的阳性率为4.7%。验证了精子介导制备转基因小鼠胚胎的可行性,并建立了利用精子载体法制备转基因小鼠胚胎的平台。     

Monitoring individual development of isolated wheat zygotes: a novel approach to study early embryogenesis

Summary A culture method has been established by which development of isolated wheat (Triticum aestivum L.) zygotes can be monitored individually until formation of multicellular structures. As was shown recently, these isolated zygotes have a high capacity to form differentiated embryos and normal plants, and thus constitute a suitable object to study early embryogenesis. After being isolated within 6 h after pollination (hap), zygotes were immobilized in an agarose droplet directly on a microscopic chamber slide, which allows for both subsequent development through co-culture with feeder aggregates, as well as detailed observation and photographic documentation of individiual behavior. Shortly after fertilization, the wheat zygote, like the unfertilized egg cell, is characterized by one conspicuous nucleolus. Typically, a second and a third nucleolus appeared between 5 and 8.5 hap. Between 7 and 15 hap, we observed nucleolar vacuolation indicating enhanced ribosomal activity. Continuous cell expansion with slight cell elongation was detected until around 15 hap, followed by a period of transitory reduction in cell volume which roughly corresponded with mitosis. Mitotic prophase of a zygote could easily be detected by the disappearance of all nucleoli within a few minutes. The division plane was generally established perpendicular to the formerly established cell elongation axis. At cytokinesis, which was completed by 19 hap in 90% of the individuals observed, 2 or 3 nucleoli were detected again per daughter cell. The first cell division, including the establishment of a cleavage furrow with intercellular spaces, was completed in all cases within 23 hap. Since this result is in accordance with what is known from earlier studies based upon fixed material, and since the zygotes subsequently continue embryogenesis, in vitro development is assumed to be analogous to that in planta. This experimental system constitutes a valuable experimental tool for further detailed research, both at the cellular and at the molecular level.Abbreviations hap hours after pollination - NOR nucleolus-organizing region     

Protein tyrosine kinase-dependent release of intracellular calcium in the sea urchin egg

The aminoguanide, methylglyoxal bis(guanylhydrazone) (MGBG), was shown to stimulate phosphorylation of RR-SRC, a synthetic protein tyrosine kinase (PTK) substrate, and different levels of tyrosyl phosphorylation of endogenous proteins in a sea urchin egg membrane-cortex preparation. Stimulating protein tyrosine kinase activity in the sea urchin egg stimulated intracellular Ca2+ release, because microinjection of 1-5 mM of MGBG into unfertilized eggs triggered a transient rise in intracellular Ca2+ activity ([Ca2+]i) after a brief latent period. Pretreating eggs with PTK-specific inhibitors, genistein or tyrphostin B42, significantly inhibited the MGBG-induced rise in [Ca2+]i. Methylglyoxal bis(guanylhydrazone) stimulation of PTK activities in the unfertilized sea urchin egg appeared to trigger Ca2+ release through phospholipase C (PLC)-dependent inositol 1,4,5-trisphosphate (InsP3) production. The MGBG-induced Ca2+ response could be suppressed in eggs preloaded with the InsP3 receptor antagonist, heparin, and was reduced in eggs pretreated with U73122, a PLC inhibitor. However, the response was unchanged in eggs treated with nicotinamide, an inhibitor of ADP-ribosyl cyclase, or nifedipine, an inhibitor of nicotinic acid adenine dinucleotide phosphate activity. These results suggest that MGBG may be useful as a chemical agonist of PTK in sea urchin eggs and allow direct testing of the PTK requirement for the transient rise in [Ca2+]i in sea urchin eggs during fertilization. Although genistein was observed to significantly delay the onset, the sperm-induced Ca2+ response in PTK inhibitor-loaded eggs otherwise appeared normal. Therefore, it was concluded that sea urchin eggs contain a PTK-dependent pathway that can mediate intracellular Ca2+ release, but PTK activity does not appear to be required for the fertilization response.     

Distribution of Lectin Binding Sites in Xenopus laevis Egg Jelly

Eggs from the anuran Xenopus laevis are surrounded by a thick jelly coat that is required during fertilization. The jelly coat contains three morphologically distinct layers, designated J1, J2, and J3. We examined the lectin binding properties of the individual jelly coat layers as a step in identifying jelly glycoproteins that may be essential in fertilization. The reactivity of 31 lectins with isolated jelly coat layers was examined with enzyme-linked lectin-assays (ELLAs). Using ELLA we found that most of the lectins tested showed some reactivity to all three jelly layers; however, two lectins showed jelly layer selectivity. The lectin Maackia amurensis (MAA) reacted only with J1 and J2, while the lectin Trichosanthes kirilowii (TKA) reacted only with J2 and J3. Some lectins were localized in the jelly coat using confocal microscopy, which revealed substantial heterogeneity in lectin binding site distribution among and within jelly coat layers. Wheat germ agglutinin (WGA) bound only to the outermost region of J3 and produced a thin, but very intense, band of fluorescence at the J1/J2 interface while the remainder of J2 stained lightly. The lectin MAA produced an intense fluorescence-staining pattern only at the J1/J2 interface. Several lectins were also tested for the ability to inhibit fertilization. WGA, MAA, and concanavalin A significantly inhibited fertilization and WGA was found to block fertilization by preventing sperm from penetrating the jelly. Using Western blotting, we identified high-molecular-weight components in J1 and J2 that may be important in fertilization.