Tomato Spotted Wilt Tospovirus Adapts to the TSWV N Gene-Derived Resistance by Genome Reassortment

ABSTRACT Pathogen- and host-derived resistance have been shown to suppress infection by many plant viruses. Tomato spotted wilt tospovirus (TSWV) is among these systems; however, it has easily overcome nearly all host resistance genes and has recently been shown to overcome resistance mediated by the TSWV N gene. To better understand the resistance-breaking mechanisms, we have chosen TSWV N gene-derived resistance (TNDR) as a model to study how plant viruses defeat resistance genes. A defined viral population of isolates TSWV-D and TSWV-10, both suppressed by TNDR, was subjected to TNDR selection by serial passage in an N-gene transgenic plant. The genotype analysis demonstrated that the mixed viral population was driven to form a specific reassortant, L(10)M(10)S(D), in the presence of TNDR selection, but remained as a heterogeneous mixture in the absence of the selection. A genotype assay of 120 local lesion isolates from the first, fourth, and seventh transfers confirmed the shift of genomic composition. Further analysis demonstrated that the individual L(10), M(10), and S(D) RNA segments were each selected independently in response to TNDR selection rather than to a mutation or recombination event. Following the seventh transfer on the N-gene transgenic plants, TSWV S RNA remained essentially identical to the S RNA from TSWV-D, indicating that no intermolecular recombination occurred between the two S RNAs from TSWV-10 and TSWV-D nor with the transferred N gene. These results support the hypothesis that TSWV utilizes genome reassortment to adapt to new host genotypes rapidly and that elements from two or more segments of the genome are involved in suppression of the resistance reaction.     

β-Tubulins in Gibberella zeae: their characterization and contribution to carbendazim resistance

BACKGROUND: Fusarium head blight caused by Gibberella zeae is an important disease of wheat and barley because it reduces grain yield and quality and results in the contamination of grain with mycotoxins. Recent studies have shown that carbendazim resistance in field strains of G. zeae is not caused by mutation of the β‐tubulin gene (β₁tub), which is the case with other filamentous fungi, but that fungicide resistance is greatly increased by deletion of β₁tub. The aim of the present study was to clarify the function of β₁tub and its role in carbendazim resistance in G. zeae by artificial gene operation. RESULTS: Deletion of β₁tub reduced vegetative growth and pathogenicity but increased asexual reproduction in G. zeae. All the mutants were more resistant to carbendazim than parent strains. A three‐dimensional model of β₁tub was constructed, and the possible carbendazim binding site was analysed. CONCLUSION: β₁tub is not an essential gene in G. zeae, but it affects the sensitivity of the fungus to carbendazim. Copyright © 2012 Society of Chemical Industry     

Genetic diversity and phylogenetic analysis of glycoprotein 5 of PRRSV isolates in mainland China from 1996 to 2006: coexistence of two NA-subgenotypes with great diversity

GP5, the most important neutralizing antigen of porcine reproductive and respiratory syndrome virus (PRRSV), has the highest genetic diversity among isolates. To more fully understand the extent of genetic diversity of PRRSV in China, we analyzed and compared the GP5 sequences of 42 PRRSV isolated from 1996 to 2006 in mainland China. We found that all of the Chinese isolates examined belong to the North American (NA) type. Among them two highly diverse subgroups were clearly demarcated on the NA-genotype phylogenetic tree. All the subgroup 1 isolates were found to be high variable in the primary neutralizing epitope and the viruses were geographically restricted to regions in southeast China. The subgroup 2 isolates shared a high identity with MLV vaccine and its parent virus VR-2332. These results may contribute to the knowledge of PRRSV epidemiology in China, and may help to explain the low efficiency of MLV or killed CH-1a vaccine to protect the subgroup 1 virus infected pigs, and the great genetic diversity should be taken into consideration for control and preventive measures.     

贵州大学学生体育达标现状浅析

采用测试、统计、调查的方法对贵州大学2000～2002年，大学三、四年级在校学生进行体育达标测试，并对测试结果进行分析、比较和研究。结果显示，只有8％的被测试者达到国家《大学生体育合格标准》的优秀等级，有18％的被测试者未能达到或通过合格等级，其不尽如人意显而易见。学生在测试过程中暴露出许多不良的考纪考风问题，也应引起我们的关注和思考。如何提高我校学生的身体素质，进一步提升体育教学水平，从政策、措施、教学手段、教学方法进行探讨。提出通过各种内部和外部的因素去激发学生积极参与体育锻炼的热情，增强学生体育锻炼的自觉性，变被动单纯的学习为自觉行为，为国家输送全面发展的合格人才。     

THE DIRECTING MECHANISM OF V-NOTCHF WITHJN V-NOTCHJNG BLASTING

Based on the blasting theory and "Fracture Mechanics " , the directing effect mechanism of V-netch in V-rotching blasting is studied and the positive splitting and directional explanding of crack within V-notching blasting and the priority of crack's expanding in the V-notch axle-plane etc are expounded. It's just these fracture characteristics mentioned above that ensure the fine control of the cracking plane.     

Experimental Investigation on Buckling Behaviors of Irregularly Shaped Aluminum Alloy Structural Components Under Axial Compression Load

The experimental and numerical investigations on buckling behaviors of aluminum alloy components with different irregularly shaped sections were carried out. The buckling load carrying capacity obtained through experiments, numerical simulations, and equations described in the design code were compared. Results obtained through experiments and numerical simulations in good agreement, which shows the validation of the numerical model. And the validated FEM model will be used for parametric analysis of buckling behavior of irregularly shaped aluminum alloy structural component. Equations in the design code do not include effects of the buckling type and need to be improved further.     

A THEORETIC BREAKDOWN CRITERION OF HYDROFRACTURING IN ROCK SALT

Experimental results of the basic mechanical properties and failure mode performed on rock salt demonstrate that rock salt is a typical and peculiar soft rock , whose" Young' s modulus/strength(E/S)"ratio is extremely small,and whose failure follows the deformation failure criterion. With these results,this paper develops a theoretic breakdown criterion of hydraulic fracturing in rock salt,which is based on the greatest tension strain failure theory and includes the vertical stress effects. It has been suggested that the critical tension strain should be determined from uniaxial compression tests. This theoretic criterion exceedingly agrees with experimental results and is applicable for every soft rock with small E/S ratio under various stresses.