Studies in the morphology and systematics of berberidaceae

The floral vasculature in three allied genera,Plagiorhegma, Jeffersoria andAchyls is investigated, and the results are compared with those ofEpimedium andVancouveria which are related closely toPlagiorhegma andJeffersonia. The vasculature in the receptacle ofPlagiorhegma andJeffersonia is similar, but that ofAchlys is much simpler. Slightly different trace patterns are observed in the sepals ofPlagiorhegma andJeffersonia. InJeffersonia, the 3-trace condition leaving 2 or 3 gaps is most frequently observed, but inPlagiorhegma traces of a double nature leaving a single gap are more frequent. The traces to the innermost sepals, petals and stamens are usually of a double nature leaving a single gap in both genera. Regular division and fusion are not observed in the receptacular stele. The vascular differentiation between sepals and petals is more advanced inPlagiorhegma andJeffersonia than inEpimedium andVancouveria. InAchlys, the traces are all staminal and single throughout their course. Two parts recognized in the pistils ofPlagiorhegma, Jeffersonia andAchlys are traversed by independent vasculature. The comparisons of pistil morphology including vasculature ofPlagiorhegma, Jeffersonia, Achlys, Epimedium andVancouveria lead to the interpretation that the pistils are based on the same morphological plan. The probable evolutionary trend in pistil is then suggested in these five genera.     

Systematic revision of the catfish genusSilurus,with description of a new species from Thailand and Burma

On the basis of external morphology and anatomy, 17 scpeies of the genusSilurus Linnaeus including a new species,S. torrentis from Thailand and Burma, are recognized as valid.S. bedfordi Regan is synonymized withS. asotus, andS. goae Haig is transferred to the genusOmpok. From an anatomical study of 12 species, the diagnostic feature of the genusParasilurus Bleeker is revealed to be invalid, and the genus is synonymized withSilurus. From the phylogenetic analysis, the genusSilurus is divided into two major species groups, thecochinchinensis group which is disributed mainly in Southeast Asia, and theglanis group which is further separated into three subgroups occurring separately in East Asia and Europe. The pattern of distribution and relationships between ontogeny and phytogeny in the genusSilurus are briefly discussed.     

Drift variances of FSTand GST statistics obtained from a finite number of isolated populations

Approximate formulas for the mean and variance of the F_STor G_ST statistic in a finite number of isolated populations are developed under the effect of random genetic drift. Computer simulation has shown that the approximate formulas give a fairly accurate result unless the initial frequency of one of the alleles involved is close to 1 and t/2N is large, where N is the effective size of a subpopulation and t is the number of generations. It is shown that when the number of subpopulations (s) is small, the mean of F_STor G_ST depends on the initial gene frequencies as well as on s. When the initial frequencies of all alleles are nearly equal to each other and the number of subpopulations is large, the distribution of F_ST in the early generations is bell-shaped. In this case Lewontin and Krakauer's k parameter is approximately 2 or less. However, if one of the initial allele frequencies is close to 1, the distribution is skewed and leptokurtic, and the k parameter often becomes larger than 2 in later generations. Thus, even under pure random genetic drift, Lewontin and Krakauer's test of selective neutrality of polymorphic genes in terms of F_ST is not always valid. It is also shown that Jacquard's approximate formula for k generally gives an overestimate.     

Infrageneric classification of the genusEleutherococcus maxim. (Araliaceae) with a new sectionCissifolius

The genusEleutherococcus Maxim, is divided into five sections based on the morphology;Eleutherococcus, Cissifolius C.H. Kim and B.-Y. Sun (sect, nov.),Acanthopanax (Decne. & Planch.) H. Ohashi,Cephalopanax (Baill.) H. Ohashi andZanthoxylopanax (Harms) H. Ohashi. SectionAcanthopanax is further divided into two subsections;Acanthopanax andIonostachyae (Nakai) C.H. Kim & B.-Y Sun (comb. nov.). The new sectCissifolius is distinguished from others in having five fused carpels with free styles, solitary umbels at the end of branches, dioecious sexuality, and absence of tufted hairs in abaxial surface of leaf veins. The new section is most closely related toAcanthopanax in having free styles, solitary umbels, and dioecious sexuality. It is also related toEleutherococcus in having five carpels and lacking tufted hairs on abaxial surface of leaves. SectionCephalopanax shares all characteristics other than the number of carpels withEleutherococcus. SectionZanthoxylopanax is closely related toAcanthopanax in having two carpels with free styles, while it is also related toCephalopanax by having bisexual flowers and umbels arranged in a simple cyme. Considering the evolutionary trend in the family Araliaceae, five-carpellate sectionsEleutherococcus andCissifolius are more primitive than two-carpellate sectionsAcanthopanax, Cephalopanax, andZanthoxylopanax. SectionZanthoxylopanax seems to be intermediate betweenAcanthopanax andCephalopanax.     

Three genes encode 3-hydroxy-3-methylglutaryl-coenzyme A reductase in Hevea brasiliensis: hmg1 and hmg3 are differentially expressed

The enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) catalyses an important step in isoprenoid biosynthesis in plants. In Hevea brasiliensis, HMGR is encoded by a small gene family comprised of three members, hmg1, hmg2 and hmg3. We have previously described hmg1 and hmg2 (Plant Mol Biol 16: 567–577, 1991). Here we report the isolation and characterization of hmg3 genomic and cDNA clones. In comparison to hmg1 which is more highly expressed in laticifers than in leaves, the level of hmg3 mRNA level is equally abundant in laticifers and leaves. In situ hybridization experiments showed that the expression of hmg3 is not cell-type specific while hmg1 is expressed predominantly in the laticifers. Primer-extension experiments using laticifer RNA showed that hmg1 is induced by ethylene while hmg3 expression remains constitutive. The hmg3 promoter, like the promoters of most house-keeping genes, lacks a TATA box. Our results suggest that hmg1 is likely to encode the enzyme involved in rubber biosynthesis while hmg3 is possibly involved in isoprenoid biosynthesis of a housekeeping nature.     

The distribution of calanoid copepods in the plankton of Wisconsin Lakes

Zooplankton communities from 499 lakes were examined for calanoid copepod species. Limnocalanus macrurus and Senecella calaloides are confined to Lakes Michigan, Superior and one inland lake each. Eurytemora affinis has recently become established in the coastal waters of Lakes Michigan and Superior. Epischura lacustris is present in the summer plankton of a wide variety of lake types. Aglaodiaptomus leptopus is sensitive to fish predation and confined to small lakes without fish. Leptodiaptomus ashlandi is restricted to Lakes Michigan and Superior, but L. sicilis is also found in some inland lakes. Leptodiaptomus minutus is a boreal species found mostly in lakes of the far north. Skistodiaptomus oregonensis is the most commonly occurring calanoid and seems well adapted to lakes of the meso-to low eutrophic types. Skistodiaptomus pallidus is also generally distributed throughout the state, but less common than oregonensis and adapted to more eutrophic lakes. Leptodiaptomus siciloides and A. clavipes are western species, adapted to eutrophic lakes, which are expanding their ranges eastward, aided by cultural eutrophication.     

Linkage of autophagy to fungal development,lipid storage and virulence in Metarhizium robertsii

Autophagy is a highly conserved process that maintains intracellular homeostasis by degrading proteins or organelles in all eukaryotes. The effect of autophagy on fungal biology and infection of insect pathogens is unknown. Here, we report the function of MrATG8, an ortholog of yeast ATG8, in the entomopathogenic fungus Metarhizium robertsii. MrATG8 can complement an ATG8-defective yeast strain and deletion of MrATG8 impaired autophagy, conidiation and fungal infection biology in M. robertsii. Compared with the wild-type and gene-rescued mutant, Mratg8Δ is not inductive to form the infection-structure appressorium and is impaired in defense response against insect immunity. In addition, accumulation of lipid droplets (LDs) is significantly reduced in the conidia of Mratg8Δ and the pathogenicity of the mutant is drastically impaired. We also found that the cellular level of a LD-specific perilipin-like protein is significantly lowered by deletion of MrATG8 and that the carboxyl terminus beyond the predicted protease cleavage site is dispensable for MrAtg8 function. To corroborate the role of autophagy in fungal physiology, the homologous genes of yeast ATG1, ATG4 and ATG15, designated as MrATG1, MrATG4 and MrATG15, were also deleted in M. robertsii. In contrast to Mratg8Δ, these mutants could form appressoria, however, the LD accumulation and virulence were also considerably impaired in the mutant strains. Our data showed that autophagy is required in M. robertsii for fungal differentiation, lipid biogenesis and insect infection. The results advance our understanding of autophagic process in fungi and provide evidence to connect autophagy with lipid metabolism.     

Organization of the origins of replication of the chromosomes of Mycobacterium smegmatis, Mycobacterium leprae and Mycobacterium tuberculosis and isolation of a functional origin from M. smegmatis

The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae.     

Nuclear DNA variation in Eu-Sorghums

There are significant differences in nuclear DNA amount between Eu-Sorghum species. The DNA variation is considerable. For example Sorghum durra has 63 per cent more DNA than Sorghum roxburghii. Increase in nuclear DNA is accompanied by increase in the mass of the nucleolus and of non-nucleolar material including the chromosomes. The ratio of DNA to non-DNA material is constant between species. The DNA concentration per unit volume at interphase in somatic nuclei and per unit of chromosome length is significantly lower in the wild species S. sudanense and S. virgatum than in the cultivated species S. caudatum, S. conspicuum, S. durra and S. roxburghii. It is suggested that the lower DNA concentration may reflect a lower proportion of heterochromatin relative to euchromatin in the wild as compared with the cultivated forms.     

Locus determining the human sperm-specific lactate dehydrogenase,LDHC, is syntenic with LDHC

From the data presented in this report, the human LDHC gene locus is assigned to chromosome 11. Three genes determine lactate dehydrogenase (LDH) in man. LDHA and LDHB are expressed in most somatic tissues, while expression of LDHC is confined to the germinal epithelium of the testes. A human LDHC cDNA clone was used as a probe to analyze genomic DNA from rodent/human somatic cell hybrids. The pattern of bands with LDHC hybridization is easily distinguished from the pattern detected by LDHA hybridization, and the LDHC probe is specific for testis mRNA. The structural gene LDHA has been previously assigned to human chromosome 11, while LDHB maps to chromosome 12. Studies of pigeon LDH have shown tight linkage between LDHB and LDHC leading to the expectation that these genes would be syntenic in man. However, the data presented in this paper show conclusively that LDHC is syntenic with LDHA on human chromosome 11. The terminology for LDH genes LDHA, LDHB, and LDHC is equivalent to Ldhl, Ldh2, and Ldh3, respectively.     

The mathematical theory of group selection. I. Full solution of a nonlinear Levins E = E(x) model

The first complete overtime solution is obtained for a group selection model of Levins E = E(x) type with recolonization but no other gene flow between islands. Assuming a subdivided population at carrying capacity, the model describes selection at a biallelic locus (A, a) where a is opposed by Mendelian selection but is favored by a lower rate of extinction of demes having high a frequency. By contrast to the linear diffusion equations encountered in classical mathematical genetics, the PDE governing the dynamics is now nonlinear in the metapopulation gene frequency distribution φ(x, t); furthermore, the initial conditions now heavily influence the equilibrium distribution φ_∞(x). A fully explicit formula (20) expressing this dependence is derived. The results indicate that a fixation is never reached, but (A, a) polymorphism in the metapopulation will result if , where s 1 parametrizes the strength of Mendelian selection, E(x) is the Levins extinction operator, h (typically in the open interval (0, 1)) is the dominance of a, and B is a parameter measuring the flatness of the initial distribution f(x) in the x → 1 limit.     

Morphometric and molecular (RAPD) analysis of six <Emphasis Type="Italic">Serapias</Emphasis> taxa from Croatia

The morphometric analyses and genetic variability assessed by RAPD markers have been used to analyse relations among six Serapias taxa from Croatia (S. istriaca, S. pulae originally described as hybrid, S. ionica, S. vomeracea, S. lingua and S. cordigera). S. istriaca distributed in southern Istria and the island of Lošinj and S. pulae stenoendemic taxon distributed only in southern Istria S. ionica is endemic to the Ionian and Dalmatian islands, while the remaining taxa are more widely distributed. The obtained results shows that the endemic S. istriaca is a well characterised taxon, that S. pulae is a hybrid between S. istriaca and S. lingua and that the hybrid is morphologically and genetically more similar to S. lingua than the second parental species S. istriaca. The division into the subsections Steno-, Medio- and Platypetalae is founded based on the floral morphology while the division into the sections Serapias and Bilamellaria is not evident in the quantitative morphological and genetic analyses. Furthermore, considerable genetic resemblance between S. vomeracea and S. ionica was established.     

The we Gene is a Modifier of the walGene in Mice

Interaction of gene wellhaarig (we) with genes waved alopecia(wal) and hairless (hr) was studied in mice. The mutant gene weis responsible for the development of a specific waved coat in homozygotes. Homozygous mice carrying mutant gene walalso have a wavy coat, though a partial alopecia develops with time in these animals. In homozygotes for thehr gene, hair loss is observed beginning from the age of ten days. A series of crosses we/weand wal/wal yielded animals with we/+wal/wal and we/we wal/wal genotypes. In micewe/+wal/wal carrying gene we at a single dose, alopecia is accelerated significantly as compared to the single-dose homozygotes +/+wal/wal. In we/we wal/wal mice, alopecia starts earlier than in we/+wal/wal mice; by the age of one month, the double homozygotes are almost hairless except for small body areas covered with a sparse coat. In addition, curliness of the first-generation hair in mice we/we wal/wal is much more expressed than in +/+wal/wal and we/we+/+ mice. The obtained evidence suggests that the wegene is a modifier of the wal gene because the former enhances the effects of the walgene, which is confirmed by the earlier onset of alopecia and progression of the latter in mice having the we/+wal/wal genotype and especially in we/we wal/wal animals. The we/we hr/+ mice do not differ in coat from we/we+/+ mice; in both cases, the coat is wavy. The coat of double homozygotes we/we hr/hr, is similar to that of we/we+/+ mice until ten days of age, when the signs of alopecia appear. By the age of 21 days, mice we/we hr/hr have lost their coat completely like mice +/+ hr/hr. Hence, the we gene is a modifier of the walgene though it does not interact with hrgene during the coat formation.     

Molecular phylogenetics of Paphiopedilum (Cypripedioideae; Orchidaceae) based on nuclear ribosomal ITS and plastid sequences

Phylogenetic relationships in the genus Paphiopedilum were studied using nuclear ribosomal internal transcribed spacer (ITS) and plastid sequence data. The results confirm that the genus Paphiopedilum is monophyletic, and the division of the genus into three subgenera Parvisepalum, Brachypetalum and Paphiopedilum is well supported. Four sections of subgenus Paphiopedilum (Pardalopetalum, Cochlopetalum, Paphiopedilum and Barbata) are recovered as in a recent infrageneric treatment, with strong support. Section Coryopedilum is also recovered, with low bootstrap but high posterior probability values for support of monophyly. Relationships in section Barbata remain unresolved, and short branch lengths and the narrow geographical distribution of many species in the section suggest that it possibly underwent rapid radiation. Mapping chromosome and genome size data (including some new genome size measurements) onto the phylogenetic framework shows that there is no clear trend in increase in chromosome number in the genus. However, the diploid chromosome number of 2n = 26 in subgenera Parvisepalum and Brachypetalum suggests that this is the ancestral condition, and higher chromosome numbers in sections Cochlopetalum and Barbata suggest that centric fission has possibly occurred in parallel in these sections. The trend for genome size evolution is also unclear, although species in section Barbata have larger genome sizes than those in other sections. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 176–196.