Malate Dehydrogenase Isozymes Research Articles

Catalytic mechanism and kinetics of malate dehydrogenase.

Malate dehydrogenase (MDH) is a ubiquitous and central enzyme in cellular metabolism, found in all kingdoms of life, where it plays vital roles in the cytoplasm and various organelles. It catalyzes the reversible NAD+-dependent reduction of L-malate to oxaloacetate. This review describes the reaction mechanism for MDH and the effects of mutations in and around the active site on catalytic activity and substrate specificity, with a particular focus on the loop that encloses the active site after the substrates have bound. While MDH exhibits selectivity for its preferred substrates, mutations can alter the specificity of MDH for each cosubstrate. The kinetic characteristics and similarities of a variety of MDH isozymes are summarized, and they illustrate that the KM values are consistent with the relative concentrations of the substrates in cells. As a result of its existence in different cellular environments, MDH properties vary, making it an attractive model enzyme for studying enzyme activity and structure under different conditions.

Acclimation to warm temperatures modulates lactate and malate dehydrogenase isozymes in juvenile Horabagrus brachysoma (Günther)

Differential expression of isozymes enables fish to tolerate temperature fluctuations in their environment. The present study explores the modulation of lactate dehydrogenase (LDH) and cytoplasmic malate dehydrogenase (sMDH) isozyme expression in the heart, muscle, brain, liver, gill, and kidney of juvenile Horabagrus brachysoma after 30 days of acclimation at 26, 31, 33, and 36°C. LDH and sMDH zymography were performed using native polyacrylamide gel electrophoresis. The zymography revealed five distinct bands of LDH isoenzymes (labelled from cathode to anode as LDH-A4, LDH-A3B1, LDH-A2B2, LDH-A1B3, and LDH-B4) and three distinct bands of sMDH isoenzymes (labelled from cathode to anode as sMDH-A2, sMDH-AB, and sMDH-B2), with considerable variation in their expression in the tissues. Acclimation to the test temperatures did not influence the expression patterns of LDH or sMDH isozymes. Densitometric analysis of individual isozyme bands revealed a reduction in the densities of bands containing the LDH-B and sMDH-B molecules, while the densities of bands containing the LDH-A and sMDH-A molecules increased in the gills and muscle, indicating the role of these organs in adaptive responses to thermal acclimation. However, the total densities of the LDH and sMDH isozymes increased with higher acclimation temperatures, indicating that adaptation to increased temperatures in H. brachysoma is primarily characterised by quantitative changes in isozyme expression.

Kinetic characterization and thermostability of C. elegans cytoplasmic and mitochondrial malate dehydrogenases

Malate dehydrogenase (MDH) catalyzes the conversion of NAD+ and malate to NADH and oxaloacetate in the citric acid cycle. Eukaryotes have one MDH isozyme that is imported into the mitochondria and one in the cytoplasm. We overexpressed and purified Caenorhabditis elegans cytoplasmic MDH-1 and mitochondrial MDH-2 in E. coli. Our goal was to compare the kinetic and structural properties of these enzymes because C. elegans can survive adverse environmental conditions, such as lack of food and elevated temperatures. In steady-state enzyme kinetics assays, we measured KM values for oxaloacetate of 54 and 52 μM and KM values for NADH of 61 and 107 μM for MDH-1 and MDH-2, respectively. We partially purified endogenous MDH-1 and MDH-2 from a mixed population of worms and separated them using anion exchange chromatography. Both endogenous enzymes had a KM for oxaloacetate similar to that of the corresponding recombinant enzyme. Recombinant MDH-1 and MDH-2 had maximum activity at 40 °C and 35 °C, respectively. In a thermotolerance assay, MDH-1 was much more thermostable than MDH-2. Protein homology modeling predicted that MDH-1 had more intersubunit salt-bridges than mammalian MDH1 enzymes, and these ionic interactions may contribute to its thermostability. In contrast, the MDH-2 homology model predicted fewer intersubunit ionic interactions compared to mammalian MDH2 enzymes. These results suggest that the increased stability of MDH-1 may facilitate its ability to remain active in adverse environmental conditions. In contrast, MDH-2 may use other strategies, such as protein binding partners, to function under similar conditions.

Do Metabolic Enzymes Explain Osmoregulation in Juvenile American Eels

During the spring, juvenile eels (Anguilla rostrata) (5-6 cm; 50-200 mg) gather in creeks along the Hudson River Tributary Estuary after migration from the Atlantic Ocean. This requires them to quickly adapt to environments with lower salt concentrations. We wondered how this is achieved. To study eels in a lab setting, we transferred them into Instant Ocean® sea salt (100% artificial sea water [ASW]) or dilutions thereof for 2 weeks; mortality was only observed in 100% ASW (37% expired in 3 hours). Interestingly, after 4 hours, 10 or 50% ASW eels showed little change in body mass, suggesting osmoregulation. While much progress has been made in understanding the mature eel response, few studies have reported enzyme activities in young eels. We hypothesized that dehydrogenases and acetylcholine esterase activities might provide a clue to explain osmoregulation and survival. Supernatants of whole juvenile eel extracts obtained from these experiments (IACUC-approved protocol) were run on 7.5% Tris-glycine PAGE gel (150V, 50 min) and the activities of non–denatured isozyme bands were analyzed with Bio-Rad ChemiDoc™ XRS+ Imager. Denatured supernatant extracts were also run on TGX 4-15% Tris-glycine PAGE gel to assess total protein banding. There was little difference in number of protein bands between eels exposed to 10% vs 50% ASW(2 and 3 weeks); however, band intensities were significantly higher for 50% ASW. Further studies revealed that two MDH (malate dehydrogenase) isozyme bands were present in extracts of eels exposed to a broad range of salinities: a relatively heavier band as mitochondrial (m) MDH and a lighter cytoplasmic (c) MDH. Activities of the mMDH bands were more robust than the cMDH bands at 50% and 10% ASW. Although the mMDH activities in eels exposed to either salinity were similar, the cMDH activities in eels exposed to 50% ASW were greater than in eels exposed to 10%. Additional experiments identified four acetylcholine esterase (AChE) isozyme bands in eel extracts; the activity of only one was significantly prominent in all exposures. Transferring the eels from 50% to 10% ASW reduced activity of the relatively heaviest isozyme band. Notably, we could not discern any fluctuations in lactate dehydrogenase (LDH) levels. In conclusion, while these preliminary findings do not reveal any concrete trends in metabolic regulation tied to survival, it does appear several key enzymes have a translational correlation tied to saline homeostasis. We acknowledge that the interpretation of these experimental results is complicated by a lack of genetic validation (i.e., sequences information and parental lines) - “nature” . In addition, the investigators were unable to track or define the environmental stresses faced during migration by individual juvenile eels before capture, which may manifest itself in unique stress responses - “nurture.”

Isozymes of malate-and lactate dehydrogenase of Astyanax bimaculatus as biomarkers of environmental impact

The activity of certain isozymes may serve as biomarkers of specific physiological conditions of living organisms. The present work aimed to evaluate malate dehydrogenase (MDH) and lactate dehydrogenase (LDH) isozymes from the hepatic, branchial and renal tissues of the fish Astyanax bimaculatus as biochemical markers of environmental changes in the Una River Basin (Taubaté, SP, Brazil). For this study, the specimens were collected in water bodies located in three sampling sites of the basin, called P1 (Itaim stream), P2 (a stream along the Remédios municipal road) and P3 (a small lake near the Dr. José Luiz Cembranelli municipal road). Physicochemical analysis of the water from these sites indicated that P1 was the less polluted site, P2 presented high levels of electrolytes in water, and P3 presented the worst water quality among the sampling sites. The isoenzymes were separated by native-PAGE and identified by their activity on the polyacrylamide gel. The results indicated that four isozymes of MDH occur in the liver of these fish, and the activities of MDH-1 and MDH-4 were detected only in fish from P2, suggesting that these isoforms have potential as biomarkers of the presence of high levels of electrolytes in water. In the kidney, MDH-1 was detected in fish from P2 and P3, but it was not detected in those from P1, suggesting that the presence of this isozyme may be a biomarker of low-quality water. The gill MDH and LDH isozyme profiles of all tissues examined showed some similarities between individuals from the three collection sites, indicating that they are not suitable as biomarkers of the environmental conditions of these sites.

Synergistic Effect of Gamma Irradiation and Entomopathogenic Fungus Beauveria bassiana on Antioxidant Isozymes of Spodoptera littoralis (Boisd.) (Lepidoptera; Noctuidae)

Molecular resistance of Spodoptera littoralis to gamma radiation and/or fungal pathogenic Beauveria bassiana via malate dehydrogenase (Mdhs) and peroxidase (Pxs) isozymes by using native- polyacrylamide gel electrophoresis was the aim of this study. Under laboratory conditions, the pathogenicity of B. bassiana against 2nd instar larvae of S. littoralis was studied. Mortality percentage increased with the time period of fungal incubation. The LC50 value of B. bassiana was (0.4×105 spore/ml) after 5 days of treatment. Analysis of gel electrophoresis revealed 4 Mdhs and 6Pxs isozyme in the 6th instar larvae of S. littoralis. Tissue extracts have been assigned according to their mobility. Gamma rays revealed disorders of the Mdhs and Pxs isozyme expression and density. Mdh1band intensity was decreased at 100 and150 Gy, while Mdh2 band intensity was decreased only at 100 Gy. Furthermore, Px1, Px2 and Px3 isozyme intensity was decreased at 100 and 150 Gy. S. littoralis exposed to 50 Gy showed resistance to radiation effects and an increase in Pxs and Mdhs bands intensity. Through the course of infection by LC50 value of B. bassiana, Mdhs and Pxs were affected and disturbed. Combined treatment of 100 Gy and B. bassiana showed synergistic effects causing marked disturbance and decrease in the isozyme pattern intensity of Mdhs and Pxs or missing Px3. However, Mdhs and Pxs isozymes intensity and expression were greatly affected after 96 h. That reflects the depression in the resistance of S. littoralis and explains the rate of mortality after 5 days post treatment.

Variasi Biokimia Genetik Populasi Ikan Betutu (Oxyeleotris marmorata, BLKr.) di Waduk Penjalin Brebes

Penjalin water reservoir in Brebes Regency, Central Java, is one of the habitats of the sand goby. A study on its genetic diversity using approaches of isozyme analysis was needed to support domestication of the fish in this area. This study was aimed at the biochemical-genetic variation of sand goby population in Penjalin water reservoir based on esterase (EST), peroxidase (PER), malate dehydrogenase (MDH), aspartate amino-transferase (AAT), and acid phosphatase (ACP) polymorphisms. Visualization of the isozymes was carried out employing horizontal electrophoretic technique with potato starch gel and buffer system of L-histidin monohydrate. Of the five isozymes, ACP was not well-visualized in all samples tested while the remaining four showed no polymorphisms. It could be concluded that there is no biochemical-genetic variation of sand goby population in Penjalin water reservoir based on isozymes of EST, PER, MDH, and AAT.

Structure of glyoxysomal malate dehydrogenase (MDH3) from Saccharomyces cerevisiae.

Malate dehydrogenase (MDH), a carbohydrate and energy metabolism enzyme in eukaryotes, catalyzes the interconversion of malate to oxaloacetate (OAA) in conjunction with that of nicotinamide adenine dinucleotide (NAD+) to NADH. Three isozymes of MDH have been reported in Saccharomyces cerevisiae: MDH1, MDH2 and MDH3. MDH1 is a mitochondrial enzyme and a member of the tricarboxylic acid cycle, whereas MDH2 is a cytosolic enzyme that functions in the glyoxylate cycle. MDH3 is a glyoxysomal enzyme that is involved in the reoxidation of NADH, which is produced during fatty-acid β-oxidation. The affinity of MDH3 for OAA is lower than those of MDH1 and MDH2. Here, the crystal structures of yeast apo MDH3, the MDH3-NAD+ complex and the MDH3-NAD+-OAA ternary complex were determined. The structure of the ternary complex suggests that the active-site loop is in the open conformation, differing from the closed conformations in mitochondrial and cytosolic malate dehydrogenases.

Molluscicidal activity and physiological toxicity of Macleaya cordata alkaloids components on snail Oncomelania hupensis

In order to search new local plant molluscicides for the control of the vectors of schistosomiasis, leaves of Macleaya cordata (Willd) R. Br. were used to extract and separate alkaloid components by thinner acid method and column chromatography, and the molluscicidal effect of alkaloid components against snail Oncomelania hupensis was determined by bioassay. The results showed that 7 alkaloid components (AN1-7) were obtained after extracting and separating alkaloids from the leaves of M. cordata, where AN2 was found being the most toxic against snail O. hupensis with 48h LC50 and LC90 values of AN2 of 6.35mg/L and 121.23mg/L, respectively. Responses of some critical enzymes to AN2, including activities of Alkaline phosphatase (ALP), Alanine aminotransferase (ALT), Aspartate transaminase (AST), Malic dehydrogenase (MDH) and Succinate dehydrogenase (SDH) in both cephalopodium and liver, were also detected through experiments, which also explored esterase isozyme (EST) exposed to AN2 in liver tissue. The results showed that AN2 significantly inhibited the activities of SDH, MDH and esterase isozyme, as AN2 significantly stimulated the activities of ALP, ALT and AST to increase at a low concentration (e.g. 25mg/L), while significantly inhibited the activities of these enzymes at a high concentration (100mg/L). These results indicated that AN2 not only inhibited protein synthesis, and respiratory chain oxidative phosphorylation, but also caused hepatocellular injury and reduced the detoxification ability of liver.

Активність і вміст ізозимів малатдегідрогенази у тканинах яєчників і матки корів впродовж статевого циклу

Активність і вміст ізозимів малатдегідрогенази у тканинах яєчників і матки корів впродовж статевого циклу

Evidence of High Gene Flow Between Samples of Horseweed (Conyza canadensis) and Hairy Fleabane (Conyza bonariensis) as Revealed by Isozyme Polymorphisms

Native polyacrylamide gel electrophoresis was used to identify polymorphisms in α- and β-esterases loci and electrophoresis in starch gel to identify polymorphism in malate dehydrogenase (MDH; EC 1.1.1.37) and acid phosphatase (ACP; EC 3.1.3.2) isozymes loci in leaf tissues from samples of horseweed and hairy fleabane populations to determine genetic diversity and population structure. Similar or differential genetic divergence between the two species may guide specific use of herbicides. For samples of plants with high genetic similarity it is possible to adopt similar mechanisms and processes for their control. The proportion of polymorphic loci was 57.14, 50.0, and 53.6%, in samples of horseweed and hairy fleabane, for EST, MDH, and ACP isozymes, respectively. A comparison of the diversity parameters in the two species showed that the number of alleles is similar in the horseweed and hairy fleabane plants. The estimated heterozygosity in horseweed and hairy fleabane was also very close. A relatively low level of population differentiation was detected between horseweed and hairy fleabane (FST= 0.0199), which suggests a substantial genetic exchange among the two species. Accordingly, estimate of gene flow was high (Nm = 12.3172) for the alleles of the lociEst,Mdh, andAcp. The Nei's identity (I) values also was high (I = 0.9561) indicating very high similarity between the twoConyzaspecies. AMOVA showed higher genetic variation within (95%) than among (5%) the two samples. The low genetic structure and high value of genetic identity was an important indication that alleles are exchanged between horseweed and hairy fleabane populations, and provides additional evidence of occurrence of outcrossing between populations or dispersion of samples of one for other site.

On the consequences of aluminium stress in rye: repression of two mitochondrial malate dehydrogenase mRNAs.

Plants have developed several external and internal aluminium (Al) tolerance mechanisms. The external mechanism best characterised is the exudation of organic acids induced by Al. Rye (Secale cereale L.), one of the most Al-tolerant cereal crops, secretes both citrate and malate from its roots in response to Al. However, the role of malate dehydrogenase (MDH) genes in Al-induced stress has not been studied in rye. We have isolated the ScMDH1 and ScMDH2 genes, encoding two different mitochondrial MDH isozymes, in three Al-tolerant rye cultivars (Ailés, Imperial and Petkus) and one sensitive inbred rye line (Riodeva). These genes, which have seven exons and six introns, were located on the 1R (ScMDH1) and 3RL (ScMDH2) chromosomes. Exon 1 of ScMDH1 and exon 7 of ScMDH2 were the most variable among the different ryes. The hypothetical proteins encoded by these genes were classified as putative mitochondrial MDH isoforms. The phylogenetic relationships obtained using both cDNA and protein sequences indicated that the ScMDH1 and ScMDH2 proteins are orthologous to mitochondrial MDH1 and MDH2 proteins of different Poaceae species. The expression studies of the ScMDH1 and ScMDH2 genes indicate that it is more intense in roots than in leaves. Moreover, the amount of their corresponding mRNAs in roots from plants treated and not treated with Al was higher in the tolerant cultivar Petkus than in the sensitive inbred line Riodeva. In addition, ScMDH1 and ScMDH2 mRNA levels decreased in response to Al stress (repressive behaviour) in the roots of both the tolerant Petkus and the sensitive line Riodeva.

Meloidogyne lopezi n. sp. (Nematoda: Meloidogynidae), a new root-knot nematode associated with coffee (Coffea arabica L.) in Costa Rica, its diagnosis and phylogenetic relationship with other coffee-parasitising Meloidogyne species

Coffee (Coffea arabica L. cv. Catuai) seedlings with abundant small root galls caused by an unknown root-knot nematode were found in southern Costa Rica. Morphology, esterase and malate dehydrogenase isozyme phenotypes and DNA markers differentiated this nematode from known Meloidogyne spp. A new species, M. lopezi n. sp., with common name Costa Rican root-knot nematode, is suggested. Meloidogyne lopezi n. sp. is distinguished from other coffee-associated Meloidogyne spp. by size of female lips and stylet, male body length and stylet and second-stage juvenile body and tail morphology. The region of the mitochondrial genome between COII and 16S rRNA showed a unique amplicon size of 1370 bp, and digestions with restriction enzymes HinfI, AluI, DraI and DraIII revealed characteristic PCR-RFLP patterns that differed from the tropical root-knot nematode species M. arabicida, M. incognita, M. izalcoensis, M. javanica and M. paranaensis. Characterisation of the protein-coding map-1 gene and phylogenetic analyses suggested that M. lopezi n. sp. might reproduce by mitotic parthenogenesis. Phylogenies estimated using Bayesian analyses based on the region between the COII and 16S rRNA mitochondrial genes, as well as the 18S and 28S ribosomal nuclear genes, indicated that M. lopezi n. sp. is closely related to other tropical Meloidogyne spp. that infect coffee, especially M. arabicida, M. izalcoensis and M. paranaensis from Central and South America. Isozyme analyses and PCR-RFLP of the COII-16S rRNA mitochondrial gene region enable a clear diagnostic differentiation between these species.

On the species status of the root-knot nematode Meloidogyne ulmi Palmisano & Ambrogioni, 2000 (Nematoda, Meloidogynidae)

The root-knot nematode Meloidogyne ulmi is synonymised with Meloidogyne mali based on morphological and morphometric similarities, common hosts, as well as biochemical similarities at both protein and DNA levels. M. mali was first described in Japan on Malus prunifolia Borkh.; and M. ulmi in Italy on Ulmus chenmoui W.C. Cheng. Morphological and morphometric studies of their holo- and paratypes revealed important similarities in the major characters as well as some general variability in a few others. Host test also showed that besides the two species being able to parasitize the type hosts of the other, they share some other common hosts. Our study of the esterase and malate dehydrogenase isozyme phenotypes of some M. ulmi populations gave a perfectly comparable result to that already known for M. mali. Finally, phylogenetic studies of their SSU and LSU rDNA sequence data revealed that the two are not distinguishable at DNA level. All these put together, leave strong evidences to support the fact that M. ulmi is not a valid species, but a junior synonym of M. mali. Brief discussion on the biology and life cycle of M. mali is given. An overview of all known hosts and the possible distribution of M. mali in Europe are also presented.

Intraspecific variability and genetic structure in Meloidogyne chitwoodi from the USA

Meloidogyne chitwoodi is a quarantine pathogen and a severe problem of potato. Intraspecific variation and genetic structure are not well characterised for M. chitwoodi, but are critical to avoid misidentification and to optimise management strategies. The objective of this study was to analyse the morphological and molecular variation of four M. chitwoodi isolates, representing all races and pathotypes currently known in the USA. Despite statistically significant morphological variation among adult females, morphometrics were not able reliably to distinguish M. chitwoodi isolates. In contrast to morphology, molecular traits that are determined by nuclear ribosomal genes were stable across all isolates. Malate dehydrogenase, esterase and superoxide dismutase isozyme phenotypes were conserved in all isolates, which is an important finding for diagnostics. To gain insight into the genetic structure of M. chitwoodi, we analysed a mitochondrial DNA segment including a partial region of COII, tRNA-His and 16S rRNA genes. Genetic structure was weak and marked by high haplotype and low nucleotide diversity. We found a high level of mitochondrial heteroplasmy in M. chitwoodi. Taken together, our results indicate that there is significant intraspecific morphological and molecular variation in M. chitwoodi. Consequences for resistance breeding in potato and directions for phylogeographic studies to trace the origin of M. chitwoodi are discussed.

First Report of Laurel Oak as a Host for the Pecan Root-Knot Nematode, Meloidogyne partityla, in Florida

Roots of laurel oak (Quercus laurifolia Michx.), member of the family Fagaceae, were found to be heavily galled by the pecan root-knot nematode, Meloidogyne partityla, in two separate home gardens between 2010 and 2012, in Alachua Co., FL. Distinct round galls were observed on secondary and tertiary roots. Internally, root-knot nematode females were clearly visible when the roots were thinly sliced and egg masses were seen protruding from the root surfaces. The nematode species identification was performed using morphology of the male stylet, selected characters of the second-stage juveniles (J2), female perineal patterns, and esterase (EST) and malate dehydrogenase (Mdh) isozyme phenotypes. Morphology of perineal patterns of females, body, stylet, and tail length of the J2 and males all matched those of the original description of M. partityla (2). A swollen deeply grooved rectum was observed in the J2. The male stylet had a blunt tip with a prominent thickening at the junction between the cone and shaft. The stylet knobs of males and females were bipartite, each incised by a deep medium longitudinal groove (2). The isozyme phenotypes (EST = Mp3; Mdh = N1a) were consistent with those previously reported for M. partityla from Florida (1). Mitochondrial DNA (mtDNA) (3) and ribosomal internal transcriber spacer (ITS) DNA (4) of females were amplified to further confirm the nematode species identification. The mtDNA amplification using the C2F3/1108 primer set (3) and the ITS amplification using a recently available M. partityla specific primer set (4) produced fragments of approximately 530 bp and 550 bp, respectively. These were consistent with those already reported for this nematode species. This first report of a plant host for the pecan root-knot nematode outside of the family Juglandaceae indicates that the nematode may have migrated from Quercus species to pecan trees during the period when orchards were being established in Florida. To our knowledge, this is the first report of the pecan root-knot nematode infecting laurel oak.

Enzyme activity and heart failure I: do lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) isozyme activities in several organs reflect pathophysiological alterations in heart failure

A recent review (Stanley et al., 2005) suggested that differential protein expression in various tissues in early stages of heart failure (HF) may contribute to symptoms. The present study investigates two enzymes, lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) to determine whether their activities show parallel changes in different tissues in control and end-stage HF dogs. LDH isozyme activities in skeletal muscle (SM), aorta (AO) and right atrium (HA) showed alterations in the banding pattern [on polyacrylamide gel electrophoresis (PAGE)] in HF animals compared to controls. Overall, LDH activity in left ventricle (HV) was comparable in both control and HF animals, though there is one less isozyme band in the HF animal. In contrast, MDH isozyme activities in HF tissues (SM, AO, HA, HV) appear to be similar in band composition and intensities to control tissues. These differential effects may reflect a subtle interplay of metabolic activities in HF organs. The present study also implies that physiological changes in end-stage HF may be due to or be a consequence of metabolic alterations in a number of organs. This work has received partial support from a Pace Scholarly Research grant.

Characterization of a new insect cell line (NTU-YB) derived from the common grass yellow butterfly, Eurema hecabe (Linnaeus) (Pieridae: Lepidoptera) and its susceptibility to microsporidia

A new lepidopteran cell line, NTU-YB, was derived from pupal tissue of Eurema hecabe (Linnaeus) (Pieridae: Lepidoptera). The doubling time of YB cells in TNM-FH medium supplemented with 8% FBS at 28 °C was 26.87 h. The chromosome numbers of YB cells varied widely from 21 to 196 with a mean of 86. Compared to other insect cell lines, the YB cells produced distinct esterase, malate dehydrogenase, and lactate dehydrogenase isozyme patterns. Identity of the internal transcribed spacer region-I (ITS-I) of YB cells to E. hecabe larvae was 96% and to Eurema blanda larvae (tissue isolated from head) was 81%. The YB cells were permissive to Nosema sp. isolated from E. blanda and the infected YB cells showed obvious cytopathic effects after 3 weeks post inoculation. The highest level of spore production was at 4 weeks post inoculation when cells were infected with the Nosema isolate, and spore production was 1.34 ± 0.9 × 10 6 spore/ml. Ultrastructrual studies showed that YB cells can host in vitro propagation of the E. blanda Nosema isolate, and developing stages were observed in the host cell nuclei as observed in the natural host, E. blanda. The NTU-YB cell line is also susceptible to Nosema bombycis.

Meloidogyne chitwoodi and Meloidogyne fallax

<i>Meloidogyne chitwoodi</i> and <i>Meloidogyne fallax</i>

Subcellular localization of isozymes of NAD-dependent malate dehydrogenase in sugar beet Beta vulgaris L.

Subcellular localization of isozymes of NAD-dependent malate dehydrogenase (MDH) in sugar beet was studied. Isozymes ss and 11 controlled by loci Mdh2 and Mdh3, respectively, were shown to locate in mitochondria, whereas isozyme pp controlled by locus Mdh1, in microbodies. All examined samples lack hybrid MDH isozymes, which could testify to the interaction between products of nonallelic Mdh genes. This can be explained by the localization of nonallelic isozymes in various compartments of the cell and organelles.