Genome expansion and gene loss in powdery mildew fungi reveal tradeoffs in extreme parasitism

Powdery mildews are phytopathogens whose growth and reproduction are entirely dependent on living plant cells. The molecular basis of this life-style, obligate biotrophy, remains unknown. We present the genome analysis of barley powdery mildew, Blumeria graminis f.sp. hordei (Blumeria), as well as a comparison with the analysis of two powdery mildews pathogenic on dicotyledonous plants. These genomes display massive retrotransposon proliferation, genome-size expansion, and gene losses. The missing genes encode enzymes of primary and secondary metabolism, carbohydrate-active enzymes, and transporters, probably reflecting their redundancy in an exclusively biotrophic life-style. Among the 248 candidate effectors of pathogenesis identified in the Blumeria genome, very few (less than 10) define a core set conserved in all three mildews, suggesting that most effectors represent species-specific adaptations.     

Genetic Variation and Population Structure of the Grape Powdery Mildew Fungus, <Emphasis Type="Italic">Erysiphe necator</Emphasis>, in Southern France

Erysiphe necator, the causative agent of powdery mildew in grapevine, was introduced into Europe from North America during the middle of the 19th century. Our objective was to analyze the genetic variation and the population structure of the fungus in southern France. The sample comprised 101 isolates and was mainly of flag shoot origin, i.e., infection of sprouting shoots after overwintering of mycelium in buds. RAPD analysis identified different haplotypes that clustered in two genetic groups (A and B). The most frequent haplotypes of each group were found in several different locations in two areas separated by 100 km and throughout the 3 year period. Several haplotypes of both groups originated from flag shoots and were recovered over successive years indicating that there is no correlation between genetic group and overwintering mode. All isolates of group A were of mating type +, but those in group B could be either + or −. Lower genotypic diversity was detected within group A than within group B. These results were consistent with the hypothesis that group A reproduces only asexually.     

Phosphinate inhibition studies of cholinesterases

The kinetic constants, K_d, k₂, and k_i, were determined for the inhibition by 4-nitro-phenyl methyl(phenyl)phosphinate of three cholinesterases: butyrylcholinesterase, bovine erythrocyte acetylcholinesterase and eel acetylcholinesterase. Stopped-flow kinetic evaluations and automated data acquisition and processing were employed. A broad range in affinity for the phosphinate inhibitor was observed as reflected by the binding constants, K_d. A similar wide range in the k₂ values for the unimolecular inhibition step was obtained. The net bimolecular rate constants, ki, indicate equal overall reactivity for butyrylcholinesterase and eel acetylcholinesterase with a smaller inhibition rate constant for bovine erythrocyte acetylcholinesterase.     

Inhibition of two acetylcholinesterases by the 4-nitrophenyl esters of methyl-, ethyl-, and isopropyl(phenyl)phosphinic acid

The inhibition of eel acetylcholinesterase and bovine erythrocyte acetylcholinesterase by the 4-nitrophenyl esters of methyl-, ethyl-, and isopropyl(phenyl)phosphinic acid (MPP, EPP, and IPP, respectively) was investigated at pH 6.90 in 0.067 M phosphate buffer (25.0°C) using stopped-flow instrumentation and automated data processing. Our evaluation of the dissociation constant, K_d, the unimolecular bonding rate constant, k₂, and the bimolecular reaction constant, k_i, are the first reported values for these constants for a homologous series of this class of organophosphorus compounds. The largest k₁ value (29,428 M^?1 sec^?1) was observed for the reaction of eel acetylcholinesterase with 4-nitrophenyl methyl(phenyl)phosphinate. The smallest k_i value (9.6 M^?1 sec^?1) was observed for the reaction of bovine erythrocyte acetylcholinesterase with 4-nitrophenyl isopropyl(phenyl)phosphinate.     

大熊猫文化历史现状及打造大熊猫文化品牌的几点思考

"国宝"大熊猫是大自然赋予人类的珍贵遗产,是生物进化奇迹和动物保护旗舰,享有无与伦比的世界知名度.但大熊猫文化却一直埋于自然,深藏闺中,鲜为人知.发掘和弘扬最古老、最有价值的大熊猫文化,进而推动和丰富大熊猫文化,逐步实现大熊猫文化品牌的市场化、战略化,是我们每一个炎黄子孙义不容辞的责任.本文分析了大熊猫文化历史发展现状、当前大熊猫文化发展存在的突出问题,提出了打造大熊猫文化品牌的几点思考:(1)用科学发展观来重新认识和定位大熊猫文化品牌及其核心价值;(2)用整合策划的手段来规划大熊猫文化品牌;(3)用市场化来打造大熊猫文化品牌;(4)推动大熊猫文化品牌产业化.