Production of native and modified recombinant Der p 1 molecules in tobacco plants

Background As a complex molecule requiring post‐translational processing, it has been difficult to produce the Der p 1 major allergen from the Dermatophagoides pteronyssinus house dust mite in a recombinant form. Objective Here, we tested whether transgenic tobacco plants are suitable to express Der p 1, either as a wild‐type molecule or as variants lacking N‐glycosylation sites (Gly^?) and/or cysteine protease activity (Enz^?). Methods Using Agrobacterium tumefaciens‐based transformation, pro Der p 1 molecules bearing mutations within either the N‐glycosylation sites (N34Q, N150Q) and/or the cysteine protease‐active site (C132V) were expressed in tobacco plants. After purification by ion exchange chromatography, allergens were characterized using immunoblotting, circular dichroism (CD), as well as basophil and T lymphocyte stimulation assays. Results Four forms of recombinant Der p 1 (i.e. wild‐type Gly⁺/Enz⁺, as well as Gly^?/Enz⁺, Gly⁺/Enz^? or Gly^?/Enz^? variants) were successfully expressed in tobacco leaves as pro Der p 1 molecules. Spontaneous cleavage of the pro‐peptide was observed in tobacco leaf extracts for all forms of recombinant Der p 1 (r Der p 1). CD confirmed that all r Der p 1 molecules, with the exception of the Gly^?/Enz^? variant, exhibited secondary structures comparable to the natural protein. A cysteine protease activity was associated only with the Gly⁺/Enz⁺ form. All these molecules exhibit a profile similar to natural Der p 1 with respect to IgE immunoreactivity, basophil activation and T cell recognition. Conclusion A tobacco plant expression system allows the production of various forms of mature Der p 1, which could be used for diagnostic or immunotherapeutic purposes.     

Cryptochrome 2 and phototropin 2 regulate resistance protein-mediated viral defense by negatively regulating an E3 ubiquitin ligase

Light harvested by plants is essential for the survival of most life forms. This light perception ability requires the activities of proteins termed photoreceptors. We report a function for photoreceptors in mediating resistance (R) protein-derived plant defense. The blue-light photoreceptors, cryptochrome (CRY) 2 and phototropin (PHOT) 2, are required for the stability of the R protein HRT, and thereby resistance to Turnip Crinkle virus (TCV). Exposure to darkness or blue-light induces degradation of CRY2, and in turn HRT, resulting in susceptibility. Overexpression of HRT can compensate for the absence of PHOT2 but not CRY2. HRT does not directly associate with either CRY2 or PHOT2 but does bind the CRY2-/PHOT2-interacting E3 ubiquitin ligase, COP1. Application of the proteasome inhibitor, MG132, prevents blue-light-dependent degradation of HRT, consequently these plants show resistance to TCV under blue-light. We propose that CRY2/PHOT2 negatively regulate the proteasome-mediated degradation of HRT, likely via COP1, and blue-light relieves this repression resulting in HRT degradation.     

Plant flotillins are required for infection by nitrogen-fixing bacteria

To establish compatible rhizobial-legume symbioses, plant roots support bacterial infection via host-derived infection threads (ITs). Here, we report the requirement of plant flotillin-like genes (FLOTs) in Sinorhizobium meliloti infection of its host legume Medicago truncatula. Flotillins in other organisms have roles in viral pathogenesis, endocytosis, and membrane shaping. We identified seven FLOT genes in the M. truncatula genome and show that two, FLOT2 and FLOT4, are strongly up-regulated during early symbiotic events. This up-regulation depends on bacterial Nod Factor and the plant''s ability to perceive Nod Factor. Microscopy data suggest that M. truncatula FLOT2 and FLOT4 localize to membrane microdomains. Upon rhizobial inoculation, FLOT4 uniquely becomes localized to the tips of elongating root hairs. Silencing FLOT2 and FLOT4 gene expression reveals a nonredundant requirement for both genes in IT initiation and nodule formation. FLOT4 is uniquely required for IT elongation, and FLOT4 localizes to IT membranes. This work reveals a critical role for plant flotillins in symbiotic bacterial infection.     

Synergy between pathogen release and resource availability in plant invasion

Why do some exotic plant species become invasive? Two common hypotheses, increased resource availability and enemy release, may more effectively explain invasion if they favor the same species, and therefore act in concert. This would be expected if plant species adapted to high levels of available resources in their native range are particularly susceptible to enemies, and therefore benefit most from a paucity of enemies in their new range. We tested this possibility by examining how resource adaptations influence pathogen richness and release among 243 European plant species naturalized in the United States. Plant species adapted to higher resource availability hosted more pathogen species in their native range. Plants from mesic environments hosted more fungi than plants from xeric environments, and plants from nitrogen-rich environments hosted more viruses than plants from nitrogen-poor environments. Furthermore, plants classified as competitors hosted more than 4 times as many fungi and viruses as did stress tolerators. Patterns of enemy release mirrored those of pathogen richness: competitors and species from mesic and nitrogen-rich environments were released from many pathogen species, while stress tolerators and species from xeric and nitrogen-poor environments were released from relatively few pathogen species. These results suggest that enemy release contributes most to invasion by fast-growing species adapted to resource-rich environments. Consequently, enemy release and increases in resource availability may act synergistically to favor exotic over native species.     

Assessment of Th1 and Th2 cytokine modulatory activity of an edible fern,Diplazium esculentum

The present study was conducted to determine the effect of Diplazium esculentum on Th1 and Th2 cytokine modulation in Swiss albino mice that were administered orally with different doses of boiled D. esculentum (BDE), daily within a span of 180 days. After the treatment, serum was collected. Splenocytes were also cultured in vitro with different concentrations of BDE, and culture supernatant was collected. Both serum and culture supernatant were used for cytokine determination by enzyme-linked immunosorbent assay (ELISA) for different Th1 (IL-2 and IFN-γ) and Th2 (IL-4 and IL-10) cytokines. Results indicated significant decreases (p < 0.05, p < 0.01, and p < 0.001) in both Th1 and Th2 cytokine concentrations when compared with their respective controls. These results suggest that the intake of D. esculentum, even after cooking, may evoke immune dysfunction by altering Th1 and Th2 cytokine balance, may induce severe immunosuppression, and may be considered as alarming.     

中国常见植物食物中植物甾醇的含量和居民摄入量初估

目的对我国植物食物中植物甾醇的含量和分布进行分析,并初步估计了中国居民膳食植物甾醇摄入量。方法选择了常见7大类约160余种植物食物样品,用气相色谱法分析了β-谷甾醇、菜油甾醇、豆甾醇、谷甾烷醇、菜油甾烷醇含量并计算总植物甾醇含量;同时利用2002年居民营养与健康状况调查结果,初步测算我国城乡居民膳食植物甾醇的日平均摄入量。结果植物甾醇含量较高的植物食物包括植物油类、坚果种子类、豆类等;谷类中面粉植物甾醇含量远高于稻米,且粮谷类食品加工越精细,植物甾醇含量越低;蔬菜水果及薯类中植物甾醇含量较低。初步估计我国居民日均植物甾醇的摄入量为322.41mg/d,谷类食物和植物油类各提供约40%的膳食植物甾醇,其他类食物提供的比例较小。结论植物甾醇含量分析和摄入量估计对科学指导膳食有重要意义。在我国膳食模式下,增加面粉类、豆类、蔬菜水果类食物的摄入量,有助于提高居民植物甾醇摄入量和减少慢性病。     

洁肤康护肤液杀菌性能的实验室观察

以当归、白芷、紫草等中药提取液为主要成分的洁肤康护肤液，稀释成０１２５％溶液，对大肠杆菌与淋病双球菌作用１ｍｉｎ，对金黄色葡萄球菌作用２ｍｉｎ，对白色念珠菌作用７ｍｉｎ，杀灭率均达９９９％以上。有机物对其杀菌作用有明显影响。该原液放置于５６℃条件下２周，杀菌效果无明显变化     

弓形虫多表位基因植物表达载体的构建

目的构建弓形虫多表位基因(TGMG)植物表达载体。方法①将TGMG亚克隆人pBAC55构建中间载体pB35MG,再将其中E35S/TGMG/NOS3′结构单元亚克隆人pCAMBIA2300构建植物表达载体pC35MG。②将番茄果实特异性启动子E81.1插入pB35MG构建中间载体pB35E1MG,再将其中E35SE81.1/TGMG/NOS3′结构单元亚克隆人pCAMBIA2300构建植物表达载体pC35E1MG。③将番茄果实特异性启动子E82.2插入pB35MG构建中间载体pBE2MG,再将其中E82.2/TGMG/NOS3′结构单元亚克隆人pCAMBIA2300构建植物表达载体pCE2MG。测序鉴定pB35MG、pC35E1MG、pCE2MG中的TGMG序列。④pC35MG、pC35E1MG、pCE2MG转化根癌农杆菌LBA404。结果重组质粒用酶切鉴定均得到预期片段,pB35MG、pC35E1MG、pCE2MG测序结果正确。结论成功构建TGMG中间载体pB35MG、pB35E1MG、pBE2MG,以及植物表达载体pC35MG、pC35E1MG、pCE2MG。并将3种植物表达载体导入根癌农杆菌。     

Heterogeneous evolutionary processes affect R gene diversity in natural populations of Solanum pimpinellifolium

Resistance (R) genes of plants are responsible for pathogen recognition and encode proteins that trigger a cascade of responses when a pathogen invades a plant. R genes are assumed to be under strong selection, but there is limited knowledge of the processes affecting R gene diversity in the wild. In this study, DNA sequence variation of Cf-2 homologs was surveyed in populations of Solanum pimpinellifolium, a wild relative of the cultivated tomato. The Cf-2 locus is involved in resistance to strains of the fungus Cladosporium fulvum. At least 26 different Cf-2 homologs were detected in natural populations of S. pimpinellifolium. These homologs differ by single base pair substitutions as well as indels in regions coding for leucine-rich repeats. Molecular population genetic analyses suggest that natural selection has acted heterogeneously on Cf-2 homologs, with selection against amino acid substitutions occurring in the 5' portion of the genes, and possible restricted positive selection in the 3' end. Balancing selection may have maintained haplotypes at the 5' end of the genes. Limited sequence exchange between genes has also contributed to sequence variation. S. pimpinellifolium individuals differ in the number of Cf-2 homologs they contain, obscuring the relationships of orthology and paralogy. This survey of Cf-2 variation in S. pimpinellifolium illustrates the wealth of R gene diversity that exists in wild plant populations, as well as the complexity of interacting genetic and evolutionary processes that generate such diversity.