The influence of the Miocene Mediterranean desiccation on the geographical expansion and genetic variation of Androcymbium gramineum (Cav.) McBride (Colchicaceae)

Chloroplast DNA (cpDNA) restriction site and isozyme data were combined to explore the spatial-temporal influence of the Messinian desiccation in the Mediterranean on the disjunct distribution of Androcymbium gramineum in Almería and Morocco (north and south of the straits of Gibraltar, respectively). Lack of evidence for different selective pressures, divergence time estimates based on the calibration of the isozyme molecular clock with the cpDNA data, the basal position of Almerian populations in the A. gramineum clade, and the much higher isozyme polymorphism in Almería suggest that (i) only a southern European range of A. gramineum existed before the Messinian [ approximately 11.2 million years ago (Ma), in the middle Miocene] and (ii) the desiccation of the Mediterranean basin about 5.5-4.5 Ma induced the migration of A. gramineum from Almería to Morocco (between 4.9 and 4.6 Ma, according to our time estimates). After the split into two allopatric units following the refilling of the Mediterranean, the major influence of drift associated with Plio-Pleistocene recurrent glaciation cycles and range expansions/contractions probably fostered the substantial interpopulation genetic differentiation observed within Almería (CGST = 0.41, average DNei = 0.185) and, to a lesser extent, within Morocco (CGST = 0.24, average DNei = 0.089), but did not hinder the maintenance of considerable levels of genetic variation in either geographical area (A = 2.14, HE = 0.230 and A = 1.90, HE = 0.213, respectively).     

A reagent less fluorescent sol-gel biosensor for uric acid detection in biological fluids

The simultaneous encapsulation of a coupled uricase-peroxidase system and amplex red in a sol-gel matrix allows one to obtain a reagent-less and ready-to-use fluorescent biosensor for the accurate detection of uric acid in highly diluted biological fluids. The detection limit of the prepared biosensor was found to be 20 nM and was linear up to 1 microM. The high sensitivity found for the biosensor permitted a reliable determination of uric acid concentrations in the presence of interfering species (e.g., ascorbic acid) just by sample dilution (up to 50000 for urine and 10000 for serum and blood). The sol-gel encapsulation preserved the hierarchy of the enzyme activity as demonstrated by the performance of the fluorescent biosensor.     

Peroxidase-catalyzed oxidation of capsaicinoids: steady-state and transient-state kinetic studies

Capsaicinoids are the pungent compounds in Capsicum fruits (i.e., "hot" peppers). Peroxidases catalyze capsaicinoid oxidation and may play a central role in their metabolism. However, key kinetic aspects of peroxidase-catalyzed capsaicinoid oxidation remain unresolved. Using transient-state methods, we evaluated horseradish peroxidase compound I and II reduction by two prominent capsaicinoids (25 degrees C, pH 7.0). We determined rate constants approaching 2 x 10(7) and 5 x 10(5)M(-1)s(-1) for compound I and compound II reduction, respectively. We also determined k(app) values for steady-state capsaicinoid oxidation approaching 8 x 10(5)M(-1)s(-1) (25 degrees C, pH 7.0). Accounting for stoichiometry, these are in excellent agreement with constants for compound II reduction, suggesting that this reaction governs capsaicinoid-dependent peroxidase turnover. Ascorbate rapidly reduced capsaicinoid radicals, assisting in the determination of the kinetic constants reported. Because ascorbate accumulates in Capsicum fruits, it may also be an important determinant for capsaicinoid content and preservation in Capsicum fruits and related products.     

Molecular evolution and structure--function relationships of the superoxide dismutase gene families in angiosperms and their relationship to other eukaryotic and prokaryotic superoxide dismutases

This study assesses whether the phylogenetic relationships between SODs from different organisms could assist in elucidating the functional relationships among these enzymes from evolutionarily distinct species. Phylogenetic trees and intron positions were compared to determine the relationships among these enzymes. Alignment of Cu/ZnSOD amino acid sequences indicates high homology among plant sequences, with some features that distinguish chloroplastic from cytosolic Cu/ZnSODs. Among eukaryotes, the plant SODs group together. Alignment of the Mn and FeSOD amino acid sequences indicates a higher degree of homology within the group of MnSODs (>70%) than within FeSODs (approximately 60%). Tree topologies are similar and reflect the taxonomic classification of the corresponding species. Intron number and position in the Cu/Zn Sod genes are highly conserved in plants. Genes encoding cytosolic SODs have seven introns and genes encoding chloroplastic SODs have eight introns, except the chloroplastic maize Sod1, which has seven. In Mn Sod genes the number and position of introns are highly conserved among plant species, but not among nonplant species. The link between the phylogenetic relationships and SOD functions remains unclear. Our findings suggest that the 5' region of these genes played a pivotal role in the evolution of function of these enzymes. Nevertheless, the system of SODs is highly structured and it is critical to understand the physiological differences between the SODs in response to different stresses in order to compare their functions and evolutionary history.     

Functional interactions between the noncovalently associated N- and C-terminal halves of mammalian Type I hexokinase

The 100 kDa Type I isozyme of mammalian hexokinase has evolved by duplication and fusion of a gene encoding an ancestral 50 kDa hexokinase. Although the N- and C-terminal halves are similar in sequence, they differ in function, catalytic activity being associated only with the C-terminal half while the N-terminal half serves a regulatory role. The N- and C-terminal halves of rat Type I hexokinase have been coexpressed in M + R 42 cells. The halves associate noncovalently to produce a 100 kDa form that exhibits characteristics seen with the intact Type I isozyme but not with the isolated catalytic C-terminal half, i.e., characteristics that are influenced by interactions between the halves. These include a decreased K(m) for the substrate ATP and the ability of P(i) to antagonize inhibition by Glc-6-P or its analog, 1-5-anhydroglucitol-6-P. Thus, functional interactions between the N- and C-terminal halves do not require their covalent linkage.     

Salicylic acid changes the properties of extracellular peroxidase activity secreted from wounded wheat (Triticum aestivum L.) roots

Summary.  Wheat (Triticum aestivum L.) roots released proteins showing peroxidase activity in the apoplastic solution in response to wound stress. Preincubation of excised roots with 1 mM salicylic acid at pH 7.0 enhanced the guaiacol peroxidase activity of the extracellular solution (so-called extracellular peroxidase). The soluble enzymes were partially purified by precipitation with ammonium sulfate followed by size exclusion and ion exchange chromatography. Despite an increase in the total activity of secreted peroxidase induced by pretreatment of excised roots with salicylic acid, the specific activity of the partially purified protein was significantly lower compared to that of the control. Purification of the corresponding proteins by ion exchange chromatography indicates that several isoforms of peroxidase occurred in both control and salicylic acid-treated samples. The activities of the extracellular peroxidases secreted by the salicylic acid-treated roots responded differently to calcium and lectins compared with those from untreated roots. Taken together, our data suggest that salicylic acid changes the isoforms of peroxidase secreted by wounded wheat roots. Received June 10, 2002; accepted September 24, 2002; published online May 21, 2003 RID="*" ID="*" Correspondence and reprints: Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia.     

Isozyme electrophoresis patterns of the liver fluke, Clonorchis sinensis from Kimhae, Korea and from Shenyang, China

An enzyme analysis of the liver fluke, Clonorchis sinensis from Kimhae, Korea and from Shenyang, China was conducted using a horizontal starch gel electrophoresis in order to elucidate their genetic relationships. A total of eight enzymes was employed from two different kinds of buffer systems. Two loci from each enzyme of aconitase and esterase (alpha-Na and beta-Na); and only one locus each from six enzymes, glucose-6-phosphate dehydrogenase (G6PD), alpha-glycerophosphate dehydrogenase (GPD), 3-hydroxybutyrate dehydrogenase (HBDH), malate dehydrogenase (MDH), phosphoglucose isomerase (PGI), and phosphoglucomutase (PGM) were detected. Most of loci in two populations of C. sinensis showed homozygous monomorphic banding patterns and one of them, GPD was specific as genetic markers between two different populations. However, esterase (alpha-Na), GPD, HBDH and PGI loci showed polymorphic banding patterns. Two populations of C. sinensis were more closely clustered within the range of genetic identity value of 0.998-1.0. In summarizing the above results, two populations of C. sinensis employed in this study showed mostly monomorphic enzyme protein banding patterns, and genetic differences specific between two populations.     

两种肚倍型蚜虫之两种同功酶及可溶性蛋白的比较

应用电泳分析方法,对青麸杨上幼锤形信子与长枣形倍子内蚜虫进行了酯酶同功酶、过氧化物同功酶及可溶蛋白质的比较研究。结果表明：经形态学鉴定同为肚倍蚜可致瘿形成纺锤形与长枣形倍子。2种倍形内蚜虫在可溶性蛋白及酯酶同功酶上有较大差异。相异系数分别为02571,0067。说明肚倍蚜种内已出现分化,不同变形体倍子内蚜虫在分子水平上已具有向不同生物型分化的趋势。     

Analysis of genetic variability of South American wild rice populations (Oryza glumaepatula) with isozymes and RAPD markers

The knowledge of population structure and genetic diversity of wild relatives of rice is needed to investigate their evolutionary history and potential use in breeding programs. Very little is known about the wild rice species ( Oryza spp.), particularly those that are native to South America. A study using isozyme and RAPD markers was conducted to estimate the level of genetic diversity of four South American wild rice populations ( Oryza glumaepatula ) recently collected in the Amazon forest and western Brazil rivers. F -statistics and genetic diversity parameters calculated from isozyme and RAPD markers indicated high values for inbreeding coefficients and differentiation among the four populations. In agreement with this, a pattern of greater variation between than within populations was observed with both types of markers. These findings were corroborated by an AMOVA analysis, which indicated that a large portion of the total genetic variation was attributed to regional divergence. The partition of the AMOVA analysis among populations showed that most of the genetic diversity was due to differences among populations. This distribution pattern of genetic variation of O. glumaepatula populations is in agreement with the expectation for an autogamous species and provides important baseline data for conservation and collection strategies for this species.     

紫外线辐射对柑桔过氧化物酶活性和电频率特性的影响

介绍了紫外线辐照柑桔后,柑桔过氧化物酶活性等生理参量和电学频率特性等物理参量随贮藏时间变化的实验结果,并对结果作了简单分析。结果表明：适当剂量的紫外辐照,可以降低柑桔的过氧化物酶活性,使柑桔电学频率特性等保持贮藏初期的特点,延缓柑桔内部结构和所含成分的变化,具有一定的保鲜效果。