山西省黍稷种质资源抗倒性鉴定及相关形态特征研究

黍稷种质的倒伏是造成黍稷减产的一大要素,如何防止黍稷的倒伏,筛选和培育抗倒的种质是解决黍稷倒伏最根本和有效的方法。通过对山西省的1192份黍稷种质资源进行抗倒性鉴定,筛选出71份高抗倒的种质。同时对高抗倒种质和不抗倒种质茎、根的形态特征进行了比较研究,证明黍稷种质的抗倒性与茎、根的形态特征有密切关系,高抗倒种质在茎、根形态特征上所占的优势是形成高抗倒的重要原因。     

Infectious plasmid resistance and efflux pump mediated resistance

Various bacterial plasmids can be eliminated from bacterial species cultured as pure or mixed bacterial cultures by non-mutagenic heterocyclic compounds at subinhibitory concentrations. For plasmid curing, the replication should be inhibited at three different levels simultaneously: the intracellular replication of plasmid DNA, partition and intercellular transconjugal transfer. The antiplasmid action of the compounds depends on the chemical structure. The targets for antiplasmid compounds were analysed in detail. It was found that amplified extrachromosomal DNA in the superhelical state binds more drug molecules than does the linear or open-circular form of the plasmid or the chromosome, without stereospecificity which leads to functional inactivation of the extrachromosomal genetic code. Plasmid elimination also occurs in ecosystems containing numerous bacterial species simultaneously, but the elimination of antibiotic resistance-encoding plasmids from all individual cells of the population is never complete. The medical significance of plasmid elimination in vitro is, it provides a method to isolate plasmid-free bacteria for biotechnology without any risk of mutations, and it opens up a new perspective in rational drug design against bacterial plasmids. Hypothetically, the combination of antiplasmid drugs and antibiotics may improve the effectivity of antibiotics against resistant bacteria; therefore, the results cannot be exploited until the curing efficiency reaches 100%. Inhibition of the conjugational transfer of antibiotic resistance plasmids can be exploited to reduce the spreading of these plasmids in ecosystems.     

Resisting resistance

This month's Genome Watch describes how knowledge of the malaria parasite genome can be used to better understand and mitigate the emergence of drug resistance.     

Nematode resistance

Plant-parasitic nematodes are major pests of both temperate and tropical agriculture. Many of the most damaging species employ an advanced parasitic strategy in which they induce redifferentiation of root cells to form specialized feeding structures able to support nematode growth and reproduction over several weeks. Current control measures, particularly in intensive agriculture systems, rely heavily on nematicides but alternative strategies are required as effective chemicals are withdrawn from use. Here, we review the different approaches that are being developed to provide resistance to a range of nematode species. Natural, R gene-based resistance is currently exploited in traditional breeding programmes and research is ongoing to characterize the molecular basis for the observed resistant phenotypes. A number of transgenic approaches hold promise, the best described being the expression of proteinase inhibitors to disrupt nematode digestion. The application of plant-delivered RNA interference (RNAi) to silence essential nematode genes has recently emerged as a potentially valuable resistance strategy.     

Replicase-mediated resistance

Transformation of a plant with a DNA sequence derived from a gene encoding a viral replicase can endow it with a high level of resistance to the virus. To date, plants have been made resistant to tobacco mosaic virus, pea early browning virus, cucumber mosaic virus and potato virus X. It is considered that expression of replicase-derived sequences at the protein level interferes with normal functioning and/or assembly of viral replicase enzyme complexes leading to a general, marked inhibition of viral replication in the cells of these transgenic plants. Analogous studies of animal viruses in tissues culture cells indicate that mutants of viral-encoded replication-associated proteins can act as inhibitors of virus replication. This paper discusses the present status and future prospects for the control of virus disease using sequences derived from viral genes encoding replicase and replication-associated proteins.     

Ivermectin resistance

In this review of ivermectin resistance, Wesley Shoop discusses the definition of resistance, catalogs all known cases of ivermectin resistance, argues that overmectins and milbemycins belong in the same action family, discusses the possibility of resistance in the filariae, and suggests that detection of ivermectin resistance is the area where future research is most needed.     

Glucocorticoid resistance

Glucocorticoids contribute fundame ntally to the maintenance of basal and stress-related homeostasis in all higher organisms. The major roles of these steroids in physiology are amply matched by their remarkable contributions to pathology. Glucocorticoid resistance is a rare familial, or sporadic condition characterized by partial end-organ insensitivity to glucocorticoids. The molecular basis of glucocorticoid resistance in several families and sporadic cases has been ascribed to mutations in the human glucocorticoid receptor α (hGRα) gene, which impair the ability of the receptor to transduce the glucocorticoid signal. Glucocorticoids are crucial for life, and therefore complete glucocorticoid resistance is uncommon. The purpose of this review is to discuss the many structural and functional features of the glucocorticoid receptor and also to evaluate the main clinical and laboratory characteristics of cortisol resistance. Published in Russian in Biokhimiyo, 2006, Vol. 71, No. 10, pp. 1328–1337.