以谷蛋白GluA-2信号肽增强外源蛋白在转基因水稻胚乳中的表达与积累

提高外源蛋白在特定目标组织器官中的表达量是转基因植物研究与开发的核心技术之一。谷蛋白是水稻种子中最主要的贮藏蛋白,其表达具有严格的时空特异性。为进一步研究谷蛋白信号肽序列在指导基因表达中的作用,本研究克隆了水稻谷蛋白Glu A-2基因的启动子及其信号肽编码序列,并与GUS报告基因编码区融合,构建了分别含有和不含有信号肽的表达载体p13GG和p13GSG;经农杆菌介导法分别转入同一水稻品种中,获得了20多个独立转化子,PCR证明外源基因都已整合进了水稻基因组中。Northern杂交结果表明,融合Glu A-2信号肽编码序列可显著提高GUS基因在水稻胚乳中的转录;利用GUS特异的抗体进行Western杂交分析,显示该信号肽序列可显著提高外源蛋白在转基因水稻胚乳中的积累,但是其所指导表达的GUS蛋白在水稻胚乳中并没有表现出相应的活性,其机制有待进一步深入解析。相关结果对于水稻品质改良基因工程研究以及以水稻种子作为生物反应器高效表达外源蛋白具有重要的指导作用。     

The role of ear environment in postharvest susceptibility of maize to toxigenic Aspergillus flavus

A kernel screening assay (KSA) was used to assess the genetic and environmental effects on the vulnerability of maize to aflatoxin accumulation. Kernels of 26 inbred lines that had been grown in seven environments, and 190 lines of the Intermated B73xMo17 (IBM) population grown in one location in the United States, were inoculated with a toxigenic strain of A. flavus and incubated in the dark at 30°C for 6 days. Percent kernel colonization (PKC), sporulation and aflatoxin were influenced by the maize genotypes (G), the location (“ear environment” or E) and the GxE interactions. Overall, low broad‐sense heritabilities were observed for PKC, sporulation and aflatoxin. PKC was significantly correlated with sporulation in all environments. Aflatoxin was positively correlated with colonization for two and with sporulation for all ear environments. Higher grain sulphur or magnesium in IBM was associated with less colonization or aflatoxin. Postharvest susceptibility of maize to aflatoxin is thus influenced by factors that are modulated by the ear environment. In a KSA, sporulation could be a proxy test for aflatoxin accumulation.     

Separating the effects of habitat amount and fragmentation on invertebrate abundance using a multi-scale framework

Context

Herbicide treatments in viticulture can generate highly contrasting mosaics of vegetated and bare vineyards, of which vegetated fields often provide better conditions for biodiversity. In southern Switzerland, where herbicides are applied at large scales, vegetated vineyards are limited in extent and isolated from one another, potentially limiting the distribution and dispersal ability of organisms.

Objectives

We tested the separate and interactive effects of habitat amount and fragmentation on invertebrate abundance using a multi-scale framework, along with additional environmental factors. We identified which variables at which scales were most important in predicting patterns of invertebrate abundance.

Methods

We used a factorial design to sample across a gradient of habitat amount (area of vegetated vineyards, measured as percentage of landscape PLAND) and fragmentation (number of vegetated patches, measured as patch density PD). Using 10 different spatial scales, we identified the factors and scales that most strongly predicted invertebrate abundance and tested potential interactions between habitat amount and fragmentation.

Results

Habitat amount (PLAND index) was most important in predicting invertebrate numbers at a field scale (50 m radius). In contrast, we found a negative effect of fragmentation (PD) at a broad scale of 450 m radius, but no interactive effect between the two.

Conclusions

The spatial scales at which habitat amount and fragmentation affect invertebrates differ, underpinning the importance of spatially explicit study designs in disentangling the effects between habitat amount and configuration. We showed that the amount of vegetated vineyards has more influence on invertebrate abundance, but that fragmentation also contributed substantially. This suggests that efforts for augmenting the area of vegetated vineyards is more beneficial for invertebrate numbers than attempts to connect them.

     

Host Plant-Based Artificial Diets Enhance Development,Survival and Fecundity of the Edible Long-Horned Grasshopper Ruspolia differens (Orthoptera: Tettigoniidae)

Wild swarms of the long-horned grasshoppers Ruspolia differens (Serville) which are widely harvested for consumption and sale in Africa are seasonal and unsustainable, hence the need for innovative ways of artificially producing the insects. We investigated the development, survival, and reproduction of R. differens in the laboratory on diets mixed with host plants [Digitaria gayana Kunth, Cynodon dactylon (L.) and Megathyrsus maximus Jacq (Poales: Poaceae); Ageratum conyzoides L. (Asterales: Asteraceae)] identified from guts of their wild conspecifics with a view to developing a suitable diet for artificial mass rearing of the edible insect. A standard diet comprising ground black soldier fly, Hermetia illucens L. (Diptera: Startiomyidae) larvae, soybean flour, maize flour, vitamin premix, and ground bones was tested for rearing R. differens as a control against the same ingredients incorporated with individual powders of the different host plants. Whereas R. differens developed more slowly in the diet mixed with D. gayana than in the control diet; its development was faster in the diet mixed with C. dactylon. Mortalities of R. differens in host plant-based diets were 42.5–52.5%, far lower than in the control diet with 71% mortality. The insects raised on the diet mixed with M. maximus laid approximately twice more eggs compared to R. differens fecundities from the rest of the diets. However, inclusion of host plants in the diets had no detectable influence on R. differens adult weight and longevity. These findings support inclusion of specific host plants in artificial diets used for mass rearing of R. differens to enhance its survival, development, and fecundity.     

Persistence and binding of DDT and gamma-HCH in a sandy loam soil under field conditions in Delhi,India

Persistence and binding capacity of [¹⁴C]p, p′-DDT and [¹⁴C]y-HCH were studied for one year in a sandy loam soil of Delhi, India, after surface treatment during monsoon, winter and summer seasons under field conditions. Both DDT and HCH dissipated more rapidly under the Indian subtropical climate than reported for temperate regions. In all three seasons, both insecticides dissipated most rapidly during the initial 60 days. However, in the final six months there was very little change in the residue levels. After one year, the final soil burden of DDT varied from 33 to 36% and of HCH from 14 to 15% of the initial concentrations in the different experiments. HCH bound more with the soil as, out of the total residues present after one year, more than 75% of HCH was in bound form compared with only 24% of DDT. The observed time for 50% initial dissipation of DDT ranged from 60 to 120 days, while in the case of HCH it varied from 30 to 45 days. However, the rate of loss of residues which persisted for more than 6 months was equivalent to a half-life of between 500 and 10000 days for DDT, and between 700 and 2000 days for HCH, thus illustrating the very long persistence of aged residues. Since degradation of both insecticides was apparently minimal, the data indicate that dissipation of DDT and HCH was largely due to volatilisation.     

Study of cattle persistently infected with bovine viral diarrhea virus that lack detectable virus in serum

OBJECTIVE: To determine whether cattle persistently infected with bovine viral diarrhea virus (BVDV) that lack virus detectable in serum by use of the immunoperoxidase microtiter assay (IPMA) can transmit the virus to susceptible herdmates and determine prevalence of these cattle. DESIGN: Clinical trial and serologic survey. SAMPLE POPULATION: 2 cattle and 1,952 blood samples. PROCEDURE: A persistently infected cow in which virus could not be detected in serum was housed with a BVDV-seronegative steer. Blood and nasal swab specimens were tested via virus isolation and serum virus neutralization. Parallel WBC preparations and sera from blood samples of 1,952 adult cows were screened for BVDV by use of IPMA. RESULTS: The steer seroconverted to BVDV within 4 weeks of contact with the cow. Virus was detected in sera and WBC of 5 adult cows that were verified as persistently infected by retest 3 weeks later. Cattle persistently infected with BVDV in which virus could not be detected in both serum and WBC by use of IPMA were not found. CONCLUSION AND CLINICAL RELEVANCE: Cattle persistently infected with BVDV in which virus cannot be detected in serum by use of IPMA may serve as virus reservoirs for infecting susceptible cattle. Persistent infection was detected at a prevalence of 0.26%. Screening adult cattle by use of IPMA on serum samples appears to be a reliable means of detecting persistent infection with BVDV. Prevalence of cattle persistently infected with BVDV that have negative results of IPMA on serum is extremely low.