bluuebunny/crossref_metadata_2025 huggingface dataset:
Host‐pathogen relationship of geographically diverse isolates of Septoria tritici and wheat cultivars
Authors: AHMED H. U. , MUNDT C. C. , COAKLEY S. M.
Published: April 2007

Pathogenic variability of 14 Septoria tritici isolates from different locations in the USA (California, Oregon, and Texas) was determined on seedlings of two sets of geographically diverse wheat cultivars under greenhouse conditions. Significant isolate effects, cultivar effects, and isolate × cultivar interactions were found, and a substantial amount of variation was accounted for by the interaction terms compared with the main effects of isolate and cultivar. All isolates were pathogenic on the cultivars tested but the degree of virulence on the individual cultivars varied among isolates. Linear contrasts between all homologous combinations (isolate × cultivar combination of same geographic location) and all heterologous combinations (isolate × cultivar combination of different locations) indicated that homologous combinations produced significantly more disease than heterologous combinations. The results demonstrate location‐specific adaptation of S. tritici. Implications of pathogenic variability and local adaptation in S. tritici are discussed.
Population diversity of Pseudomonas syringae subsp. savastanoi on olive and oleander
Authors: CAPONERO A. , CONTESINI A. M. , IACOBELLIS N. S.
Published: April 2007

Twenty‐one strains of Pseudomonas syringae subsp. savastanoi, isolated from knots on olive and oleander trees growing in close proximity to or in physical contact with one another, were evaluated for knot induction and for bacteriocin production. In addition, DNA preparations from the bacterial strains were tested for hybridization to probes containing the tryptophan monooxygenase (iaaM) and isopentenyl transferase (ipt) genes, which are involved in indole‐3‐acetic acid and cytokinin biosynthesis, respectively, in P.s. subsp. savastanoi.

The strains showed features characteristic of strains usually isolated from their respective host plants. For example, all 10 oleander strains were virulent both to oleander and olive, did not produce bacteriocins and harboured the iaaM gene on plasmids. In contrast, all 11 olive strains were virulent only to olive, 10 strains produced bacteriocins, and nine strains carried the iaaM gene on the chromosome. Two olive strains (OAll, OD21) harboured the gene coding for iaaM on plasmids. Furthermore, strain OD21 carried the iaaM gene on the same plasmid as the ipt gene. This is the first report both of a plasmid‐borne iaaM in typical olive strains (virulent only to olive and bacteriocin producers), and of the presence of the ipt gene on the same plasmid. In olive and oleander strains the ipt gene was located either on plasmids or on the chromosome. These results suggest that under natural conditions the pathogen does not appear to spread from oleander to olive even when trees are growing in close proximity or in physical contact.

The location of the phytohormone genes on plasmids or on the chromosome is discussed in relationship to bacteriocin‐production and knot‐induction on the host species.
The reliability of visual estimates of disease severity on cereal leaves
Authors: PARKER S. R. , SHAW M. W. , ROYLE D. J.
Published: April 2007

Visual estimates of wheat disease severity were compared with actual severities determined using image analysis of tracings of diseased leaves. Septoria tritici, leaf senescence and Erysiphe graminis were studied. Observer estimates were widely scattered about the actual severities (i.e. they were imprecise), differed substantially from the actual severities even after averaging (i.e. they were inacctirate), and varied considerably over short time‐scales. Relative bias decreased with increasing disease severity. In a comparison of three seed treatments to control powdery mildew on winter barley, visual assessment errors altered the conclusions of the experiment. Two treatments were statistically indistinguishable on the basis of visual severity estimates, while estimates obtained by image analysis showed that one seed treatment was twice as effective as the other.
Susceptibility of pines in South Africa to the pitch cankerfungus subglutinansf.sp. pini
Authors: VILJOEN A. , WINGFIELD M. J. , KEMP G. H. J. , MARASAS W. F O.
Published: April 2007

Fusarium subglutinans f.sp. pini (F.s. pini)is the causal agent of pitch canker of pines. The fungus has recently been found in South Africa on the diseased roots of seedlings, but has as yet not been detected on mature trees in commercial forests. Inoculation of 1 ‐year‐old and seedlings with isolates of resulted in canker development and shoot mortality. No significant differences in virulence were found among eight isolates of the pathogen on and but isolate MRC 6214 was significantly more virulent on seedlings than MRC 6209. Disease development was significantly more severe on and than on Pathogenicity tests on 4‐year‐old and trees yielded comparable results. Resinous cankers, similar to those described for pitch canker, developed on trees in the vicinity of inoculation points but development ceased before stems were girdled.
Biological control of Fusarium oxysporum f. sp. lycopersici
Authors: DE CAL A. , PASCUAL S. , LARENA I. , MELGAREJO P.
Published: April 2007

Fungi known to produce lytic enzymes were used in an attempt to control wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (FOL). Some of the fungal species (Penicillium oxalicum, Penicillium purpurogenum and Aspergillus nidulans) damaged hyphae of FOL in vitro and reduced the numbers of microconidia in the soil. Treatments with fungi did not result in a reduction in either chlamydospores of FOL in soil or populations of FOL in the rhizosphere of tomato. P. oxalicum was the most effective agent of biocontrol, and it reduced disease severity in both non‐autoclaved (20% decrease) and sterile soil. In sterile soil, P. oxalicum reduced disease with different levels of severity (27% decrease at high levels and 50% decrease at low levels). Disease control by A. nidulans and P purpurogenum was only achieved when disease severity was low in sterile soil (55% and 45%, respectively).
Incidence of bacteria inhibitory to Erwinia amylovora from blossoms in New Zealand apple orchards
Authors: KEARNS L. P. , HALE C. N.
Published: April 2007

Populations of total bacteria and Erwinia herbicola were monitored on apple blossom in selected orchards at two different geographical regions in New Zealand (Canterbury and Hawke's Bay). In all four orchards surveyed E. herbicola populations remained negligible (less than 50cfu/blossom) throughout flowering, increasing rapidly at petal drop to reach levels of 1 × 103 cfu/blossom (Hawke's Bay) to 1 × 105 cfu/blossom (Canterbury). Total bacterial populations increased 100‐fold at petal drop in both locations. Pseudomonas populations were predominant in Canterbury throughout all flowering stages and in Hawkes Bay after early flowering. When screened for inhibitory activity to E. amylovora, 26% of all isolates from Canterbury showed some inhibition in vitro, but none of the isolates from Hawke's Bay showed inhibition of E. amylovora in vitro. Two Canterbury isolates with strong in vitro inhibitory activity also inhibited E. amylovora in immature pear fruit. One isolate was identified as E. herbicola and one isolate as Pseudomonas fluorescens.
Plant‐pathogen interactions of sunflower and Macrophomina phaseolina in vitro and in vivo
Authors: DAY J. P. , MacDONALD M. V.
Published: April 2007

The relative pathogenicity of isolates of Macrophomina phaseolina was comparable both on sunflower tissue cultures and on mature plants and seedlings. The relative susceptibility of the different sunflower lines in vitro showed a similar pattern for cotyledon callus cultures, but not for immature embryo cultures. Although these protocols appear to be unsuitable for the selection of novel disease resistance, they do offer the potential for a rapid, non‐destructive screen for resistant material.
Recombination and selection in populations of plant pathogens
Authors: BROWN J. K. M.
Published: April 2007

A theoretical model has been used to study the dynamics of the frequencies of the following: a virulence gene which is selected by part of the host plant population; an unnecessary virulence gene, which is not required for infection of the host; and the gametic disequilibrium between the two genes. If the two genes are not initially in gametic equilibrium, the frequency of the unnecessary virulence may be altered greatly by hitch‐hiking selection, because of the increased frequency of the selected virulence. The hitchhiking effect is strongest if reproduction is entirely asexual, but can still be significant if the frequency of recombination is less than the fraction of the host population which consists of selectively resistant plants. The frequency of recombination may be reduced if reproduction is partly clonal, rather than fully sexual, or if the two genes are linked. Selection against unnecessary virulence may give rise to complex dynamics of both virulence alleles; in particular, the frequency of an unnecessary virulence can rise substantially, by hitch‐hiking selection, even if there is some sex or recombination. The direction in which the unnecessary virulence's frequency changes depends on the sign of the gametic disequilibrium between it and the selected gene, and on the existence of selection against unnecessary virulence. If there is no such selection, the long‐term dynamics of genotype frequencies in a largely asexual pathogen population may be unpredictable. Consequently, disease control strategies based on planned replacements of one resistance gene by another are unlikely to be effective.
Electrophoretic karyotype variation among pathotypes of Fusarium oxysporum f.sp. dianthi
Authors: MIGHELI Q. , BERIO T. , GULLINO M. L. , GARIBALDI A.
Published: April 2007

Karyotype analysis by pulsed‐field gel electrophoresis was applied to characterize isolates of Fusarium oxysporum f.sp. dianthi, the causal agent of Fusarium wilt on carnation. Eleven distinct chromosomal DNA patterns were detected among 38 pathogenic isolates, and the total genome size was estimated to range from 23·7 to 36·4 Mb. Except for isolates belonging to pathotypes 2 and 4, all members of the same pathotype shared overlapping electrophoretic karyotypes. Karyotypes of isolates assigned to pathotypes 1 and 8 showed a high degree of similarity, in accordance with VCG and RFLP analysis. The same electrophoretic karyotype was also shared by members of pathotypes 2 and 5, thus confirming results obtained by both VCG and RFLP grouping, A single representative of pathotype 6, previously confined to the same VCG and RFLP group as pathotypes 2 and 5, had a slightly different chromosomal pattern. Isolates assigned to pathotype 4 showed four related karyotypes which partially differed in both the number and size of chromosomal bands. However, all strains assigned to this pathotype shared a basic profile of nine chromosomal bands, while two low‐molecular‐weight bands were present or absent. The findings are discussed with regard both to the suitability of race distinction in the case of the special form dianthi of F. oxysporum and to the use of karyotype analysis by PFGE as a tool for the study of the population genetics of this fungus.
Histopathological changes associated with silverleaf syndrome in squash
Authors: RAMOS L. J. , BHARATHAN N. , McMILLAN R. T. , NARAYANAN K. R.
Published: April 2007

Silverleaf syndrome on squash (Cucurbita pepo) is characterized by vein clearing, and leaf whitening, and has been associated with the presence of nymphs of Bemisia tabaci (sweetpotato whitefly), and the presence of two double‐stranded RNAs (4·2 and 4·6 kb) in symptomatic leaves. However, the aetiology of the disorder remains unknown. Anatomical studies using transverse and paradermal sections from symptomatic leaves of C. pepo cv. Dixie showed turgescent, aligned adaxial epidermal cell layer, flat cuticle and the presence of sub‐epidermal spaces. Histochemical studies failed to reveal any breakdown in the cellulose cell walls; however, the cuticular layer, the pectin layer and cellulose wall of epidermal cells formed a fiat compact structure. Some changes were observed in the lipid content, with the presence of lipid bodies near cell wall membranes. Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis of preparations of symptomatic squash leaves, partially purified by differential centrifugation, revealed a protein with a molecular mass of about 48 k Da that was not found in comparable preparations of asymptomatic leaves. This protein was localized by immunological staining in the spongy mesophyll cells and in the layer of bundle sheath associated with sieve elements and companion cells of the leaf phloem.
Survival of Didymella rabiei in chickpea straw debris in Spain
Authors: NAVAS‐CORTÉS J. A. , TRAPERO‐CASAS A. , JIMÉNEZ‐DÍAZ R. M.
Published: April 2007

Didymella rabiei grew saprophytically on pieces of infested chickpea stems and pods, and formed pycnidia and pseudothecia. The extent of saprophytic growth and production of viable spores were determined by the incubation conditions. On debris left on the soil surface under natural conditions, the fungus rapidly colonized the tissues, formed abundant pseudothecia and pycnidia, and remained viable throughout the 2 years of the study. When plant debris was buried, D, rabiei was restricted to the original lesions, in which it formed new pycnidia and was viable for 2 to 5 months. Under controlled conditions in the laboratory, D. rabiei extensively colonized plant debris spread over the soil surface. On the other hand, the fungus did not grow on buried debris, or showed only very limited development when the artificially infested debris was buried between two layers of sterilized soil. Incubation temperature was the principal factor associated with the production of conidia and especially ascospores.
Culture in vitro of Rhododendron and Erysiphe sp.
Authors: KENYON D. M. , DIXON G. R. , HELFER S.
Published: April 2007

Successful dual cultures of a powdery mildew pathogen and Rhododendron ponticum plantlets were achieved using a tissue culture technique. Sporulation was observed within 1 week of inoculation. Comparative in vitro cultures were grown at 10, 15 and 20°C with host tissue transferred to fresh media at 2‐monthly intervals. Viable conidia capable of infecting host tissue in vivo were obtained from cultures maintained at 10 and 15°C after culture for more than 6 months. Isolates from three sources (Auchincruive, Benmore and Perth) were introduced into culture. Cultures inoculated with Perth and Benmore isolates exhibited increased host growth at 10 and 15°C, respectively compared with control plantlets. These effects may result from pathogen‐induced changes to host regulatory metabolism. The culture technique allows the long‐term maintenance of pathogen cultures under sterile conditions without requiring subculture.
Effect of method of inoculation, inoculum density and seedling age at inoculation on the expression of resistance of cocoa (Theobroma cacao L.) to Verticillium dahliae Kleb.
Authors: RESENDE M. L. V. , FLOOD J. , COOPER R. M.
Published: April 2007

Soil drench and stem puncture inoculation were compared as methods for selecting cocoa cultivars with resistance to Verticillium dahliae. Disease progress was more rapid and induced symptoms were more severe following stem puncture and, under glasshouse conditions, differences between cultivars were detected 15 days after inoculation. Moreover, using stem puncture, inoculum densities of 104 conidia/ml were sufficient to differentiate resistant and susceptible cultivars, whereas with the soil drench method, inoculum densities of 107 conidia/ml were necessary. Although a substantially higher proportion of plants were affected by stem puncture inoculation, the resistance of cultivar Pound‐7 remained effective at high inoculum densities of 108 conidia/ml. With either method, older seedlings were more susceptible to V. dahliae than younger ones. However, with stem puncture, 15‐day‐old seedlings were sufficiently susceptible for a valid disease assessment. In contrast, with soil inoculation, 60‐day‐old plants were required. In a nursery trial with 15‐day‐old seedlings, seven cocoa genotypes previously selected as resistant, moderately resistant or susceptible to Verticillium dahliae, on the basis of root inoculation, were ranked in the same order when stem punctured. Stem puncture inoculation of young seedlings is cost‐effective in terms of time and space, and is therefore recommended for screening of cocoa for wilt resistance, especially in large‐scale breeding programmes.
Effect of male sterility on ergot disease spread in wheat
Authors: MANTLE P. G. , SWAN D. J.
Published: April 2007

Cytoplasmic male‐sterile winter wheat, grown in the field in England with a limited supply of pollen, set over 80% less seed than fertile wheat. Wheat ears precociously inoculated with ergot (Claviceps purpurea) initiated local natural epidemics of disease at flowering and, within 1‐5m of primary foci, sclerotial abundance at harvest was correlated inversely with seed set, Sclerotial mass in poorly pollinated male‐sterile wheat comprised more than 20% of the threshed grain yield, in contrast to only 0.7% in fertile wheat.
AAP1 transports uncharged amino acids into roots of Arabidopsis
Authors: Lee Yong‐Hwa , Foster Justin , Chen Janet , Voll Lars M. , Weber Andreas P.M. , Tegeder Mechthild
Published: April 2007

Amino acids are available to plants in some soils in significant amounts, and plants frequently make use of these nitrogen sources. The goal of this study was to identify transporters involved in the uptake of amino acids into root cells. Based on the fact that high concentrations of amino acids inhibit plant growth, we hypothesized that mutants tolerating toxic levels of amino acids might be deficient in the uptake of amino acids from the environment. To test this hypothesis, we employed a forward genetic screen for Arabidopsis thaliana mutants tolerating toxic concentrations of amino acids in the media. We identified an Arabidopsis mutant that is deficient in the amino acid permease 1 (AAP1, At1g58360) and resistant to 10 mm phenylalanine and a range of other amino acids. The transporter was localized to the plasma membrane of root epidermal cells, root hairs, and throughout the root tip of Arabidopsis. Feeding experiments with [14C]‐labeled neutral, acidic and basic amino acids showed significantly reduced uptake of amino acids in the mutant, underscoring that increased tolerance of aap1 to high levels of amino acids is coupled with reduced uptake by the root. The growth and uptake studies identified glutamate, histidine and neutral amino acids, including phenylalanine, as physiological substrates for AAP1, whereas aspartate, lysine and arginine are not. We also demonstrate that AAP1 imports amino acids into root cells when these are supplied at ecologically relevant concentrations. Together, our data indicate an important role of AAP1 for efficient use of nitrogen sources present in the rhizosphere.
Phytochrome coordinates Arabidopsis shoot and root development
Authors: Salisbury Frances J. , Hall Anthony , Grierson Claire S. , Halliday Karen J.
Published: April 2007

The phytochrome family of photoreceptors are potent regulators of plant development, affecting a broad range of responses throughout the plant life cycle, including hypocotyl elongation, leaf expansion and apical dominance. The plant hormone auxin has previously been linked to these phytochrome‐mediated responses; however, these studies have not identified the molecular mechanisms that underpin such extensive phytochrome and auxin cross‐talk. In this paper, we show that phytochrome regulates the emergence of lateral roots, at least partly by manipulating auxin distribution within the seedling. Thus, shoot‐localized phytochrome is able to act over long distances, through manipulation of auxin, to regulate root development. This work reveals an important role for phytochrome as a coordinator of shoot and root development, and provides insights into how phytochrome is able to exert such a powerful effect on growth and development. This new link between phytochrome and auxin may go some way to explain the extensive overlap in responses mediated by these two developmental regulators.
Overexpression of CRK13, an Arabidopsis cysteine‐rich receptor‐like kinase, results in enhanced resistance to Pseudomonas syringae
Authors: Acharya Biswa R. , Raina Surabhi , Maqbool Shahina B. , Jagadeeswaran Guru , Mosher Stephen L , Appel Heidi M. , Schultz Jack C. , Klessig Daniel F. , Raina Ramesh
Published: April 2007

Protein kinases play important roles in relaying information from perception of a signal to the effector genes in all organisms. Cysteine‐rich receptor‐like kinases (CRKs) constitute a sub‐family of plant receptor‐like kinases (RLKs) with more than 40 members that contain the novel C‐X8‐C‐X2‐C motif (DUF26) in the extracellular domains. Here we report molecular characterization of one member of this gene family, CRK13. Expression of this gene is induced more quickly and strongly in response to the avirulent compared with the virulent strains of Pseudomonas syringae, and peaks within 4 h after pathogen infection. In response to dexamethasone (DEX) treatment, plants expressing the CRK13 gene from a DEX‐inducible promoter exhibited all tested features of pathogen defense activation, including rapid tissue collapse, accumulation of high levels of several defense‐related gene transcripts including PR1, PR5 and ICS1, and accumulation of salicylic acid (SA). In addition, these plants suppressed growth of virulent pathogens by about 20‐fold compared with the wild‐type Col‐0. CRK13‐conferred pathogen resistance is salicylic acid‐dependent. Gene expression analysis using custom cDNA microarrays revealed a remarkable overlap between the expression profiles of the plants overexpressing CRK13 and the plants treated with Pst DC3000 (avrRpm1). Our studies suggest that upregulation of CRK13 leads to hypersensitive response‐associated cell death, and induces defense against pathogens by causing increased accumulation of salicylic acid.
Arbuscular mycorrhizal symbiosis is accompanied by local and systemic alterations in gene expression and an increase in disease resistance in the shoots
Authors: Liu Jinyuan , Maldonado‐Mendoza Ignacio , Lopez‐Meyer Melina , Cheung Foo , Town Christopher D. , Harrison Maria J.
Published: April 2007

In natural ecosystems, the roots of many plants exist in association with arbuscular mycorrhizal (AM) fungi, and the resulting symbiosis has profound effects on the plant. The most frequently documented response is an increase in phosphorus nutrition; however, other effects have been noted, including increased resistance to abiotic and biotic stresses. Here we used a 16 000‐feature oligonucleotide array and real‐time quantitative RT‐PCR to explore transcriptional changes triggered in Medicago truncatula roots and shoots as a result of AM symbiosis. By controlling the experimental conditions, phosphorus‐related effects were minimized, and both local and systemic transcriptional responses to the AM fungus were revealed. The transcriptional response of the roots and shoots differed in both the magnitude of gene induction and the predicted functional categories of the mycorrhiza‐regulated genes. In the roots, genes regulated in response to three different AM fungi were identified, and, through split‐root experiments, an additional layer of regulation, in the colonized or non‐colonized sections of the mycorrhizal root system, was uncovered. Transcript profiles of the shoots of mycorrhizal plants indicated the systemic induction of many genes predicted to be involved in stress or defense responses, and suggested that mycorrhizal plants might display enhanced disease resistance. Experimental evidence supports this prediction, and mycorrhizal M. truncatula plants showed increased resistance to a virulent bacterial pathogen, Xanthomonas campestris. Thus, the symbiosis is accompanied by a complex pattern of local and systemic changes in gene expression, including the induction of a functional defense response.
QQT proteins colocalize with microtubules and are essential for early embryo development in Arabidopsis
Authors: Lahmy Sylvie , Guilleminot Jocelyne , Schmit Anne‐Catherine , Pelletier Georges , Chaboute Marie‐Edith , Devic Martine
Published: April 2007

During Arabidopsis embryogenesis, the control of division between daughter cells is critical for pattern formation. Two embryo‐defective (emb) mutant lines named quatre‐quart (qqt) were characterized by forward and reverse genetics. The terminal arrest of qqt1 and qqt2 embryos was at the octant stage, just prior to the round of periclinal divisions that establishes the dermatogen stage . Homozygous embryos of a weaker allele of qqt1 were able to divide further, resulting in aberrant periclinal divisions. These phenotypic analyses support an essential role of the QQT proteins in the correct formation of the tangential divisions. That an important proportion of qqt1 embryos were arrested prior to the octant stage indicated a more general role in cell division. The analysis of QQT1 and QQT2 genes revealed that they belong to a small subgroup of the large family encoding ATP/GTP binding proteins, and are widely conserved among plants, vertebrates and Archaea. We showed that QQT1 and QQT2 proteins interact with each other in a yeast two‐hybrid system, and that QQT1 and QQT2 tagged by distinct fluorescent probes colocalize with microtubules during mitosis, in agreement with their potential role in cell division and their mutant phenotype. We propose that QQT1 and QQT2 proteins participate in the organization of microtubules during cell division, and that this function is essential for the correct development of the early embryo.
RNA silencing and its cell‐to‐cell spread during Arabidopsis embryogenesis
Authors: Kobayashi Ken , Zambryski Patricia
Published: April 2007

In plants, post‐transcriptional RNA silencing (PTGS) signals move beyond their sites of synthesis using channels called plasmodesmata (PD). However, a potential influence of PD permeability in silencing signal movement has not been addressed previously. PD connectivity and aperture are routinely determined by monitoring the cell‐to‐cell movement of protein tracers of different sizes. Here we compare protein and RNA silencing signal movement during Arabidopsis embryogenesis. The data suggest that the degree of PTGS signal movement correlates with the degree of PD aperture previously determined in distinct subregions of the developing Arabidopsis embryo. Silencing signals move more extensively in the hypocotyl and root compared with the area around the tips of the cotyledons, suggesting that the site of silencing signal initiation influences the extent of signal movement. In addition, we found a putative boundary for silencing spread just below the shoot apical meristem that blocks movement upward from the root and hypocotyl. Finally, as PD aperture affects protein movement in embryos, we compared the movement patterns of protein tracers versus the movement patterns of RNA silencing signals. The data reveal that silencing signal complexes move to a similar extent as soluble proteins between 27–54 kDa.
Transcriptome profiling of maize anthers using genetic ablation to analyze pre‐meiotic and tapetal cell types
Authors: Ma Jiong , Duncan David , Morrow Darren J. , Fernandes John , Walbot Virginia
Published: April 2007

Oligonucleotide arrays were used to profile gene expression in dissected maize anthers at four stages: after‐anther initiation, at the rapid mitotic proliferation stage, pre‐meiosis, and meiotic prophase I. Nearly 9200 sense and antisense transcripts were detected, with the most diverse transcriptome present at the pre‐meiotic stage. Three male‐sterile mutants lacking a range of normal cell types resulting from a temporal progression of anther failure were compared with fertile siblings at equivalent stages by transcription profiles. The msca1 mutant has the earliest visible phenotype, develops none of the normal anther cell types and exhibits the largest deviation from fertile siblings. The mac1 mutant has an excess of archesporial derivative cells and lacks a tapetum and middle layer, resulting in moderate transcriptional deviations. The ms23 mutant lacks a differentiated tapetum and shows the fewest differences from fertile anthers. By combining the data sets from the comparisons between individual sterile and fertile anthers, candidate genes predicted to play important roles during maize anther development were assigned to stages and to likely cell types. Comparative analyses with a data set of anther‐specific genes from rice highlight remarkable quantitative similarities in gene expression between these two grasses.
Environmental and hormonal regulation of the activity–dormancy cycle in the cambial meristem involves stage‐specific modulation of transcriptional and metabolic networks
Authors: Druart Nathalie , Johansson Annika , Baba Kyoko , Schrader Jarmo , Sjödin Andreas , Bhalerao Rupali R. , Resman Lars , Trygg Johan , Moritz Thomas , Bhalerao Rishikesh P.
Published: April 2007

We have performed transcript and metabolite profiling of isolated cambial meristem cells of the model tree aspen during the course of their activity–dormancy cycle to better understand the environmental and hormonal regulation of this process in perennial plants. Considerable modulation of cambial transcriptome and metabolome occurs throughout the activity–dormancy cycle. However, in addition to transcription, post‐transcriptional control is also an important regulatory mechanism as exemplified by the regulation of cell‐cycle genes during the reactivation of cambial cell division in the spring. Genes related to cold hardiness display temporally distinct induction patterns in the autumn which could explain the step‐wise development of cold hardiness. Factors other than low temperature regulate the induction of early cold hardiness‐related genes whereas abscisic acid (ABA) could potentially regulate the induction of late cold hardiness‐related genes in the autumn. Starch breakdown in the autumn appears to be regulated by the ‘short day’ signal and plays a key role in providing substrates for the production of energy, fatty acids and cryoprotectants. Catabolism of sucrose and fats provides energy during the early stages of reactivation in the spring, whereas the reducing equivalents are generated through activation of the pentose phosphate shunt. Modulation of gibberellin (GA) signaling and biosynthesis could play a key role in the regulation of cambial activity during the activity–dormancy cycle as suggested by the induction of PttRGA which encodes a negative regulator of growth in the autumn and that of a GA‐20 oxidase, a key gibberellin biosynthesis gene during reactivation in spring. In summary, our data reveal the dynamics of transcriptional and metabolic networks and identify potential targets of environmental and hormonal signals in the regulation of the activity–dormancy cycle in cambial meristem.
Receptor‐like protein kinase 2 (RPK 2) is a novel factor controlling anther development in Arabidopsis thaliana
Authors: Mizuno Shinji , Osakabe Yuriko , Maruyama Kyonoshin , Ito Takuya , Osakabe Keishi , Sato Takahide , Shinozaki Kazuo , Yamaguchi‐Shinozaki Kazuko
Published: April 2007

Receptor‐like kinases (RLK) comprise a large gene family within the Arabidopsis genome and play important roles in plant growth and development as well as in hormone and stress responses. Here we report that a leucine‐rich repeat receptor‐like kinase (LRR‐RLK), RECEPTOR‐LIKE PROTEIN KINASE2 (RPK2), is a key regulator of anther development in Arabidopsis. Two RPK2 T‐DNA insertional mutants (rpk2‐1 and rpk2‐2) displayed enhanced shoot growth and male sterility due to defects in anther dehiscence and pollen maturation. The rpk2 anthers only developed three cell layers surrounding the male gametophyte: the middle layer was not differentiated from inner secondary parietal cells. Pollen mother cells in rpk2 anthers could undergo meiosis, but subsequent differentiation of microspores was inhibited by tapetum hypertrophy, with most resulting pollen grains exhibiting highly aggregated morphologies. The presence of tetrads and microspores in individual anthers was observed during microspore formation, indicating that the developmental homeostasis of rpk2 anther locules was disrupted. Anther locules were finally crushed without stomium breakage, a phenomenon that was possibly caused by inadequate thickening and lignification of the endothecium. Microarray analyses revealed that many genes encoding metabolic enzymes, including those involved in cell wall metabolism and lignin biosynthesis, were downregulated throughout anther development in rpk2 mutants. RPK2 mRNA was abundant in the tapetum of wild‐type anthers during microspore maturation. These results suggest that RPK2 controls tapetal cell fate by triggering subsequent tapetum degradation, and that mutating RPK2 impairs normal pollen maturation and anther dehiscence due to disruption of key metabolic pathways.
Differentiating bipolar disorder in Turkish prepubertal children with attention‐deficit hyperactivity disorder
Authors: Diler Rasim Somer , Uguz Sukru , Seydaoglu Gulsah , Erol Nese , Avci Ayse
Published: April 2007

Background:  Attention‐deficit hyperactivity disorder (ADHD) and bipolar disorder (BPD) in children are frequently comorbid conditions. Because the coexistence of ADHD and mania seriously complicates the course of the condition and the treatment of children, diagnosing or missing this comorbidity has important clinical implications. There are very few systematic studies on the subject in the literature and BPD in children is not recognized or studied in most countries other than the USA. We aimed to differentiate Turkish prepubertal children with ADHD from those with comorbid ADHD and BPD and compare their clinical characteristics.

Methods:  A total of 147 treatment‐ and drug‐naïve children, aged 7 to 13 years, who had been consecutively referred to the ADHD clinic, were evaluated using the Schedule for Affective Disorders and Schizophrenia for School‐age Children–Present and Lifetime version (K–SADS–PL). Parents completed the Child Behavior Checklist (CBCL) 4–18 and the Parent–Young Mania Rating Scale (P–YMRS) prior to the clinical interview.

Results:  Twelve children (8.2%) had comorbid bipolar disorder (ADHD + BPD). The ADHD + BPD group had significantly higher rates of depressive disorders, oppositional defiant disorder, panic disorder and a family history of bipolar disorder compared with the ADHD group. The ADHD + BPD group had significantly more problems on the CBCL scale (anxiety/depression, social problems, thought problems, aggression, externalization, and total score) and on the P–YMRS (all items except for insight) compared with the ADHD group.

Conclusions:  We conclude that ADHD + BPD in Turkish children represents a clinical picture different to that of ADHD alone, in which the clinical characteristics resemble those of children reported in the literature. Further long‐term follow‐up studies are needed in larger clinical and community samples.
Anticonvulsant efficacy of valproate‐like carboxylic acids: a potential target for anti‐bipolar therapy
Authors: Azab Abed N , Greenberg Miriam L
Published: April 2007

Background:  Bipolar disorder (BPD) is a severe and chronic illness, with a lifetime prevalence of approximately 1.5%. Despite the availability of some mood stabilizing drugs including lithium, valproate (valproic acid), lamotrigine and carbamazepine, BPD is characterized by high rates of recurrence, as treatment with these and other drugs is ineffective for and not well‐tolerated by a significant percentage of patients. Most drugs currently used for the maintenance treatment of BPD are anticonvulsants (e.g., valproate, carbamazepine and lamotrigine).

Objectives:  The aim of this paper is to review the studies characterizing the anticonvulsant efficacy of valproate‐like carboxylic acids and related compounds, some of which may have potential for the treatment of manic‐depressive illness.

Results:  The data reviewed herein demonstrate clearly that some dietary fatty acids and other valproate‐like carboxylic acids exhibit potent anticonvulsant activity, and may thus be candidates for mood stabilizing treatment options for BPD.
Effects of mood stabilizers on the inhibition of adenylate cyclase via dopamine D2‐like receptors
Authors: Montezinho Liliana P , Mørk Arne , Duarte Carlos B , Penschuck Silke , Geraldes Carlos FGC , Castro M Margarida CA
Published: April 2007

Objective:  The mood stabilizing drugs lithium, carbamazepine and valproate modulate brain adenosine monophosphate (cAMP) levels, which are assumed to be elevated in bipolar disorder patients. The aim of this work was to investigate how these three mood stabilizing agents affect the regulation of cAMP levels by dopamine D2‐like receptors in vitro in rat cortical neurons in culture and in vivo in the rat prefrontal cortex.

Methods:  The production of cAMP was measured in the cultured cortical neurons or in microdialysis samples collected from the prefrontal cortex of freely moving rats using the [8‐3H] and [125I] radioimmunoassay kits.

Results:  In vitro and in vivo data showed that the treatment with the mood stabilizing drugs had no effect on basal cAMP levels in vitro, but had differential effects in vivo. Direct stimulation of adenylate cyclase (AC) with forskolin increased cAMP levels both in vitro and in vivo, and this effect was significantly inhibited by all three mood stabilizers. Activation of dopamine D2‐like receptors with quinpirole partially inhibited forskolin‐induced increase in cAMP in untreated cultures, but no effect was observed in cortical neuron cultures treated with the mood stabilizing drugs. Similar results were obtained by chronic treatment with lithium and valproate in the prefrontal cortex in vivo. However, surprisingly, in carbamazepine‐treated rats the activation of dopamine D2‐like receptors enhanced the responsiveness of AC to subsequent activation by forskolin, possibly as a consequence of chronic inhibition of the activity of the enzyme.

Conclusions:  It was shown that each of these drugs affects basal‐ and forskolin‐evoked cAMP levels in a distinct way, resulting in differential responses to dopamine D2‐like receptors activation.
Manic symptoms and impulsivity during bipolar depressive episodes
Authors: Swann Alan C , Gerard Moeller F , Steinberg Joel L , Schneider Laurie , Barratt Ernest S , Dougherty Donald M
Published: April 2007

Objectives:  In contrast to the extensive literature on the frequent occurrence of depressive symptoms in manic patients, there is little information about manic symptoms in bipolar depressions. Impulsivity is a prominent component of the manic syndrome, so manic features during depressive syndromes may be associated with impulsivity and its consequences, including increased risk of substance abuse and suicidal behavior. Therefore, we investigated the prevalence of manic symptoms and their relationships to impulsivity and clinical characteristics in patients with bipolar depressive episodes.

Methods:  In 56 bipolar I or II depressed subjects, we investigated the presence of manic symptoms, using Mania Rating Scale (MRS) scores from the Schedule for Affective Disorders and Schizophrenia (SADS), and examined its association with other psychiatric symptoms (depression, anxiety, and psychosis), age of onset, history of alcohol and/or other substance abuse and of suicidal behavior, and measures of impulsivity.

Results:  MRS ranged from 0 to 29 (25th–75th percentile, range 4–13), and correlated significantly with anxiety and psychosis, but not with depression, suggesting the superimposition of a separate psychopathological mechanism. Impulsivity and history of substance abuse, head trauma, or suicide attempt increased with increasing MRS. Receiver‐operating curve analysis showed that MRS could divide patients into two groups based on history of alcohol abuse and suicide attempt, with an inflection point corresponding to an MRS score of 6.

Discussion:  Even modest manic symptoms during bipolar depressive episodes were associated with greater impulsivity, and with histories of alcohol abuse and suicide attempts. Manic symptoms during depressive episodes suggest the presence of a potentially dangerous combination of depression and impulsivity.
Adverse pregnancy outcomes in mothers with affective psychosis
Authors: MacCabe James H , Martinsson Lennart , Lichtenstein Paul , Nilsson Emma , Cnattingius Sven , Murray Robin M , Hultman Christina M
Published: April 2007

Objectives:  Affective psychosis has its peak incidence during the childbearing years, but little is known about the effects of the illness on pregnancy. We investigated risks of preterm delivery (PTD), low birthweight (LBW), births of infants small for their gestational age (SGA), stillbirth and infant death in births to mothers with affective psychosis using a nested case–control design within a cohort of 1,558,071 singleton births in Sweden during 1983–1997.

Methods:  Using prospectively collected data from population registers, we compared the pregnancy outcomes of 5,618 births to women with affective psychosis with the outcomes of 46,246 births to unaffected mothers.

Results:  Mothers with affective psychosis had elevated risk for giving birth to preterm, small or growth‐retarded babies. The risk for stillbirth and infant death during the first year of life was not significantly higher. The risks were greatest in mothers receiving hospital treatment for affective disorder during pregnancy: (i) preterm delivery: odds ratio (OR) = 2.67, 95% confidence interval (CI) = 1.71–4.17; (ii) SGA: OR = 2.36; 95% CI = 1.34–4.16; (iii) low birthweight: OR = 2.22; 95% CI = 1.31–3.76; and (iv) stillbirth: OR = 2.19; 95% CI = 0.55–8.76. After adjustment for covariates, particularly smoking, the risks were attenuated but remained significant.

Conclusions:  Clinicians should be aware of the increased risk of adverse pregnancy outcomes in women with affective psychosis, some of which may be preventable.
Age and ratings of manic psychopathology
Authors: Young Robert C , Kiosses Dimitris , Heo Moonseong , Schulberg Herbert C , Murphy C , Klimstra Sibel , DeAsis Jose M , Alexopoulos George S
Published: April 2007

Objectives:  Clinicians have suggested that manic psychopathology in adulthood changes with advanced age. We used rating scale evaluations of manic psychopathology in adult patients with bipolar (BP) disorder to test whether older age is associated with scores on items related to excesses of behaviors: i.e., Sexual Interest, Increased Activity‐Energy, Speech – Rate and Amount, and Disruptive–Aggressive Behavior.

Methods:  The association of Young Mania Rating Scale item scores with current age was studied in symptomatic inpatients meeting DSM‐IV criteria for BP disorder, manic.

Results:  The sample consisted of 149 patients ranging in age from 18 to 89 years; 48 of these were male. Age was not associated with differences in overall severity reflected in total score. Age was associated with lower scores on the Sexual Interest item (r = − 0.26, p < 0.001). A trend for higher scores with age on Speech – Rate and Amount (r = 0.19, p < 0.02) did not meet criteria for significance. Increased Activity‐Energy, Disruptive–Aggressive Behavior and other item scores were not associated with age. In an exploratory analysis, age and Sexual Interest and Speech item scores were associated in female patients but not in male patients.

Conclusions:  These findings suggest that age minimally influences manic psychopathology in patients with BP disorder. The modest correlation between age and Sexual Interest item scores warrants further investigation and the trend for an association between age and Speech – Rate and Amount can be examined in future studies. Possible gender differences in the associations between age and these item scores also invite future study.
Hospitalization risks in the treatment of bipolar disorder: comparison of antipsychotic medications
Authors: Gianfrancesco Frank , Rajagopalan Kitty , Goldberg Joseph F , Wang Ruey‐Hua
Published: April 2007

Objectives:  This study compared the relative risk for hospitalization of patients with bipolar and manic disorders receiving atypical and typical antipsychotics.

Methods:  This retrospective study was based on administrative claims data extracted from the PharMetrics database during 1999 through 2003. Comparisons were made among atypical antipsychotics (risperidone, olanzapine, quetiapine or ziprasidone), as well as between each of these versus a combined group of the leading typical antipsychotics. Relative risk for hospitalization was estimated with Cox proportional regression, which adjusted for differences in patient characteristics.

Results:  Risperidone and olanzapine demonstrated higher risks for hospitalization than quetiapine [hazard ratio (HR) 1.19, p < 0.05 for both], translating into higher annual mental health inpatient charges of $260 per patient. Risperidone and olanzapine also showed higher estimated risks than ziprasidone, which approached the p < 0.05 threshold. Differences between each of the atypicals and the combined typicals were not significant. Patients with putative rapid cycling had a threefold greater risk for hospitalization than other patients with bipolar disorder. In these patients, comparisons among atypical antipsychotics showed that risperidone had a significantly higher hospitalization risk than olanzapine (HR 3.31, p < 0.05), resulting in higher annual mental health inpatient charges of $4,930 per patient.

Conclusions:  In the treatment of bipolar and manic disorders, risperidone and olanzapine were associated with a higher risk for hospitalization than quetiapine, and possibly ziprasidone. In the treatment of putative rapid cyclers, olanzapine was associated with a lower risk for hospitalization than risperidone.
Context processing performance in bipolar disorder patients
Authors: Brambilla Paolo , MacDonald Angus W , Sassi Roberto B , Johnson Melissa K , Mallinger Alan G , Carter Cameron S , Soares Jair C
Published: April 2007

Objectives:  Context processing is the adaptive control of current behavior through the use of prior context information. It has been found to be impaired in schizophrenia. Some studies have indicated that, compared with patients with schizophrenia, those with bipolar disorder (BPD) display a similar but less severe neuropsychological pattern of impairment. However, this cognitive dimension has not yet been examined in BPD patients in the existing literature.

Methods:  An expectancy version of the AX continuous performance test (AX‐CPT) was administered to 15 bipolar outpatients and 26 healthy controls. Patients with schizophrenia, in which context processing deficits are known to occur, were used as a reference group.

Results:  Bipolar patients showed a context processing deficit relative to healthy controls, although this was less severe and generalized than in schizophrenia patients.

Conclusions:  These findings suggest there are milder impairments in context processing in BPD compared with schizophrenia. However, the severity of possible context processing deficits in BPD may have been underestimated in our sample of mostly euthymic outpatients.