bluuebunny/crossref_metadata_2025 huggingface dataset:
Function and regulation of phospholipid signalling in plants
Authors: Xue Hong-Wei , Chen Xu , Mei Yu
Published: July 2009

As an important metabolic pathway, phosphatidylinositol metabolism generates both constitutive and signalling molecules that are crucial for plant growth and development. Recent studies using genetic and molecular approaches reveal the important roles of phospholipid molecules and signalling in multiple processes of higher plants, including root growth, pollen and vascular development, hormone effects and cell responses to environmental stimuli plants. The present review summarizes the current progress in our understanding of the functional mechanism of phospholipid signalling, with an emphasis on the regulation of Ins(1,4,5)P3–Ca2+ oscillation, the second messenger molecule phosphatidic acid and the cytoskeleton.
Solving the eigenvalue equations of correlated vibrational structure methods: Preconditioning and targeting strategies
Authors: Győrffy W. , Seidler P. , Christiansen O.
Published: July 2009

Various preconditioners and eigenvector targeting strategies in combination with the Davidson and Olsen methods are presented for solving eigenvalue equations encountered in vibrational configuration interaction, its response generalization, and vibrational coupled cluster response theory. The targeting methods allow significant flexibility and robustness in computing selected vibrational states, which are particularly important in the often occurring but nontrivial cases of near degeneracies. We have investigated the effect of a mode-excitation level-based generally applicable preconditioning scheme aiming to improve the robustness of the more standard diagonal preconditioning method. Although increasing convergence rates may be achieved in general through a hierarchy of these preconditioners, the strategy is not always beneficial in terms of CPU time. Features of the methods are demonstrated in calculations of the overtone vibrational states of formaldehyde and the fundamental states of vinyl fluoride, vinyl chloride, vinyl bromide, and naphthalene.
Radial propagation of geodesic acoustic modes
Authors: Hager Robert , Hallatschek Klaus
Published: July 2009

The GAM group velocity is estimated from the ratio of the radial free energy flux to the total free energy applying gyrokinetic and two-fluid theory. This method is much more robust than approaches that calculate the group velocity directly and can be generalized to include additional physics, e.g., magnetic geometry. The results are verified with the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)], the two-fluid code NLET [K. Hallatschek and A. Zeiler, Phys. Plasmas 7, 2554 (2000)], and analytical calculations. GAM propagation must be kept in mind when discussing the windows of GAM activity observed experimentally and the match between linear theory and experimental GAM frequencies.
Solution-processed InGaZnO-based thin film transistors for printed electronics applications
Authors: Lim Jun Hyung , Shim Jong Hyun , Choi Jun Hyuk , Joo Jinho , Park Kyung , Jeon Haseok , Moon Mi Ran , Jung Donggeun , Kim Hyoungsub , Lee Hoo-Jeong
Published: July 2009

This letter reports the utility of using the sol-gel process for exploring the library of multicomponent ZnO-based oxides as an active layer of thin film transistors. We chose InGaZnO as a starting material and modulated the Ga content to examine the potential of this material. Increasing the Ga ratio from 0.1 to 1 brought about a dynamic shift in the electrical behavior from conductor to semiconductor. This exploratory work critically helped us fabricate a device with robust device performance (a mobility of 1∼2 cm2 V−1 s−1 for the 400 °C-sintered samples and 0.2 cm2 V−1 s−1 for the 300 °C-sintered samples).
Nanosecond magnetic switching of ferromagnet-antiferromagnet bilayers in thermally assisted magnetic random access memory
Authors: Hérault J. , Sousa R. C. , Ducruet C. , Dieny B. , Conraux Y. , Portemont C. , Mackay K. , Prejbeanu I. L. , Delaët B. , Cyrille M. C. , Redon O.
Published: July 2009

The magnetic switching of the exchange biased storage layer in thermally assisted magnetic random access memory cells has been studied in the nanosecond time domain. Under reversed static external field, the magnetic tunnel junctions (MTJs) were subjected to current heating pulses long enough to heat the structure above the blocking temperature of the antiferromagnetic layer. The magnetic response of the storage layer was characterized by single-shot real-time measurement of MTJ resistance. The switching of the storage layer exhibits stochastic fluctuations. Nevertheless, using a heating current density of 4.7×106 A/cm2 corresponding to a bias voltage of 1.8 V, the switching takes place in less than 4 ns under 5 mT. Interestingly, the probability of switching versus pulse duration exhibits characteristic periodic steps which are ascribed to a combined effect of the applied field and spin transfer produced by the heating current pulses.
Double pulse ultrafast laser ablation of nickel in vacuum
Authors: Donnelly T. , Lunney J. G. , Amoruso S. , Bruzzese R. , Wang X. , Ni X.
Published: July 2009

We have studied ultrafast laser ablation of nickel using a pair of identical ≈250 fs 527 nm laser pulses separated by ≈1 to ≈1000 ps. Scanning white light interferometry was used to measure the ablated volume, and an ion probe was used to measure the angular distribution of the ablation plasma plume and the total ion emission. As the delay of the second pulse increased from ≈10 to 100 ps the ablated volume decreased by more than a factor of 2; indeed it falls to a value below the single pulse case. Conversely, it is found that the ion yield is sharply increased in this delay regime. It seems that both these features can be explained by the interaction of the second laser pulse with the ablated material produced by the first pulse.
Ga-implantation in Ge: Electrical activation and clustering
Authors: Impellizzeri G. , Mirabella S. , Irrera A. , Grimaldi M. G. , Napolitani E.
Published: July 2009

The electrical activation and clustering of Ga implanted in crystalline Ge was investigated in the (0.3–1.2)×1021 Ga/cm3 concentration range. To this aim, Ge samples implanted with 50 keV gallium, and annealed at several temperatures up to 650 °C, have been subjected to a detailed structural and electrical characterization. The substrate was maintained at 77 K during implantation to avoid the formation of the honeycomb structure that occurs during implantation at room temperature of heavy ions at high fluence. Secondary ion mass spectrometry analyses indicated a negligible Ga diffusion and dopant loss during the thermal annealing. The carrier concentration in the recrystallized samples measured by Hall effect showed a maximum concentration of active Ga of ∼6.6×1020 Ga/cm3. A remarkable Ga deactivation occurred with increasing the annealing temperature from 450 to 650 °C although the sheet resistance did not change considerably in this temperature range. It turned out that the carrier concentration reduction is balanced by the enhancement of the hole mobility that exhibits a steep variation with the concentration of the ionized scattering centers in this range. A simple model is proposed to explain the experimental results taking into account the thermally activated Ga clustering. These studies, besides clarifying the mechanism of Ga deactivation in Ge, can be helpful for the realization of future generation devices based on Ge.
Rotationally resolved ultrahigh-resolution laser spectroscopy of the S2 A11←S A11 transition of azulene
Authors: Semba Yosuke , Yoshida Kazuto , Kasahara Shunji , Ni Chi-Kung , Hsu Yen-Chu , Lin Sheng Hsien , Ohshima Yasuhiro , Baba Masaaki
Published: July 2009

We have observed rotationally resolved ultrahigh-resolution fluorescence excitation spectra of the 000 (a-type) and 000+467 cm−1 (b-type) bands of the S2 A11←S0 A11 transition of jet-cooled azulene. The observed linewidth is 0.0017 cm−1, which corresponds to the lifetime of 3.1 ns in the S2 state. Zeeman splitting of rotational lines is very small so that intersystem crossing to the triplet state is considered to be very slow. Inertial defect is very small and the molecule is considered to be planar in the S0 and S2 states (C2v symmetry). Rotational constants of the S2 state are almost identical to those of the S0 state, indicating that geometrical structure is similar in both electronic states. In this case, internal conversion (IC) by vibronic coupling is thought to be inactive. Therefore, the main radiationless transition process in the S2 A11 state of azulene was identified to be IC to the S1 B12 state. However, this S2→S1 IC is still slower than that of conventional polycyclic aromatic hydrocarbons. We consider it to be due to the shallower potential energy curve in the S1 B12 state, which is also responsible for the extraordinarily fast S1→S0 IC in the isolated azulene molecule.
Physical aging in glassy o-terphenyl monitored by probe rotation
Authors: Syutkin V. M. , Grebenkin S. Yu.
Published: July 2009

The physical aging of o-terphenyl was studied through its influence on the rotation rate of probe molecules (1-naphthylazomethoxybenzene) over a temperature range from 231 (Tg−12 K) to 238.5 K (Tg−4.5 K). An optical anisotropy decay technique was used to monitor the molecule rotation. The rotation slows down strongly as the aging proceeds. It was shown that the aging dynamics is spatially heterogeneous. The anisotropy decay is well described under the following assumptions: (i) the temperature and structure dependencies of the relaxation time follow the Scherer–Hodge equation and (ii) the time of rotation is proportional to the time of structural relaxation.
Experimental determination of the spring constant of an individual multiwalled carbon nanotube cantilever using fluorescence measurement
Authors: Kwon Soongeun , Park Hyojun , Shim Hyung Cheoul , Lee Hyung Woo , Kwak Yoon Keun , Kim Soohyun
Published: July 2009

We report an experimental method to determine the spring constant of a multiwalled carbon nanotube (MWNT) cantilever as a mechanical piconewton force transducer. Electrostatic actuation was employed to investigate the mechanical properties of a MWNT cantilever. In order to measure nanotube’s deflection during actuation, fluorescent dyes were noncovalently attached to the end of the nanotubes. Also, the length dependence of the spring constant is studied by adjusting the length of MWNT via electrochemical etching. The results show that the spring constant of a MWNT cantilever is as small as 0.001 N/m and tunable in the range of 0.001–0.05 N/m.
Zinc chlorins for artificial light-harvesting self-assemble into antiparallel stacks forming a microcrystalline solid-state material
Authors: Ganapathy Swapna , Sengupta Sanchita , Wawrzyniak Piotr K. , Huber Valerie , Buda Francesco , Baumeister Ute , Würthner Frank , de Groot Huub J. M.
Published: July 2009

We introduce a concept to solve the structure of a microcrystalline material in the solid-state at natural abundance without access to distance constraints, using magic angle spinning (MAS) NMR spectroscopy in conjunction with X-ray powder diffraction and DFT calculations. The method is applied to a novel class of materials that form (semi)conductive 1D wires for supramolecular electronics and artificial light-harvesting. The zinc chlorins 3-devinyl-3
1
-hydroxymethyl-13
2
-demethoxycarbonylpheophorbide a (3′,5′-bis-dodecyloxy)benzyl ester zinc complex 1 and 3-devinyl-3
1
-methoxymethyl-13
2
-demethoxycarbonylpheophorbide a (3′,5′-bis-dodecyloxy)benzyl ester zinc complex 2, self-assemble into extended excitonically coupled chromophore stacks.
1
H-
13
C heteronuclear dipolar correlation MAS NMR experiments provided the
1
H resonance assignment of the chlorin rings that allowed accurate probing of ring currents related to the stacking of macrocycles. DFT ring-current shift calculations revealed that both chlorins self-assemble in antiparallel π-stacks in planar layers in the solid-state. Concomitantly, X-ray powder diffraction measurements for chlorin 2 at 80 °C revealed a 3D lattice for the mesoscale packing that matches molecular mechanics optimized aggregate models. For chlorin 2 the stacks alternate with a periodicity of 0.68 nm and a 3D unit cell with an approximate volume of 6.28 nm
3
containing 4 molecules, which is consistent with space group
P
2
1
22
1
.
Interactions between mutualist
Wigglesworthia
and tsetse peptidoglycan recognition protein (PGRP-LB) influence trypanosome transmission
Authors: Wang Jingwen , Wu Yineng , Yang Guangxiao , Aksoy Serap
Published: July 2009

Tsetse flies, the sole vectors of African trypanosomes, have coevolved with mutualistic endosymbiont
Wigglesworthia glossinidiae
. Elimination of
Wigglesworthia
renders tsetse sterile and increases their trypanosome infection susceptibility. We show that a tsetse peptidoglycan recognition protein (PGRP-LB) is crucial for symbiotic tolerance and trypanosome infection processes. Tsetse
pgrp-lb
is expressed in the
Wigglesworthia
-harboring organ (bacteriome) in the midgut, and its level of expression correlates with symbiont numbers. Adult tsetse cured of
Wigglesworthia
infections have significantly lower
pgrp-lb
levels than corresponding normal adults. RNA interference (RNAi)-mediated depletion of
pgrp-lb
results in the activation of the immune deficiency (IMD) signaling pathway and leads to the synthesis of antimicrobial peptides (AMPs), which decrease
Wigglesworthia
density. Depletion of
pgrp-lb
also increases the host's susceptibility to trypanosome infections. Finally, parasitized adults have significantly lower
pgrp-lb
levels than flies, which have successfully eliminated trypanosome infections. When both PGRP-LB and IMD immunity pathway functions are blocked, flies become unusually susceptible to parasitism. Based on the presence of conserved amidase domains, tsetse PGRP-LB may scavenge the peptidoglycan (PGN) released by
Wigglesworthia
and prevent the activation of symbiont-damaging host immune responses. In addition, tsetse PGRP-LB may have an anti-protozoal activity that confers parasite resistance. The symbiotic adaptations and the limited exposure of tsetse to foreign microbes may have led to the considerable differences in
pgrp-lb
expression and regulation noted in tsetse from that of closely related
Drosophila
. A dynamic interplay between
Wigglesworthia
and host immunity apparently is influential in tsetse's ability to transmit trypanosomes.
Structure of human Rad51 protein filament from molecular modeling and site-specific linear dichroism spectroscopy
Authors: Reymer Anna , Frykholm Karolin , Morimatsu Katsumi , Takahashi Masayuki , Nordén Bengt
Published: July 2009

To get mechanistic insight into the DNA strand-exchange reaction of homologous recombination, we solved a filament structure of a human Rad51 protein, combining molecular modeling with experimental data. We build our structure on reported structures for central and N-terminal parts of pure (uncomplexed) Rad51 protein by aid of linear dichroism spectroscopy, providing angular orientations of substituted tyrosine residues of Rad51-dsDNA filaments in solution. The structure, validated by comparison with an electron microscopy density map and results from mutation analysis, is proposed to represent an active solution structure of the nucleo-protein complex. An inhomogeneously stretched double-stranded DNA fitted into the filament emphasizes the strategic positioning of 2 putative DNA-binding loops in a way that allows us speculate about their possibly distinct roles in nucleo-protein filament assembly and DNA strand-exchange reaction. The model suggests that the extension of a single-stranded DNA molecule upon binding of Rad51 is ensured by intercalation of Tyr-232 of the L1 loop, which might act as a docking tool, aligning protein monomers along the DNA strand upon filament assembly. Arg-235, also sitting on L1, is in the right position to make electrostatic contact with the phosphate backbone of the other DNA strand. The L2 loop position and its more ordered compact conformation makes us propose that this loop has another role, as a binding site for an incoming double-stranded DNA. Our filament structure and spectroscopic approach open the possibility of analyzing details along the multistep path of the strand-exchange reaction.
Project Integrate: Translating Screening and Brief Interventions for Alcohol Problems to a Community Hospital Emergency Department
Authors: Mello Michael J. , Baird Janette , Nirenberg Ted D. , Smith Jennifer C. , Woolard Robert H. , Dinwoodie Robert G.
Published: July 2009

Screening and brief intervention (SBI) for alcohol problems in the emergency department (ED) is effective. The objective of this study was to examine the translation of SBI into a busy community ED environment. The authors assessed key stakeholders views of SBI delivery model, then utilized feedback to adapt model. Adoption of SBI was recorded, with data collected on use of screening tool, and referral for a BI. Model was modified due to physicians’ and nursing resistance; physicians only screened and a research assistant (RA) delivered the BI. When the RA was present, screening by ED staff increased from 50% to 71% but returned to 50% after the RA left. An identified opportunity was increased nursing interest after observation of SBI, with 15 nurses trained in SBI after ED intervention concluded. Important barriers to translating SBI to community ED clinical practice exist. However, with additional staff present, high levels of SBI can occur.
Implementing Evidence-Based Practices in Community Treatment Programs: Initial Feasibility of a Counselor “Toolkit”
Authors: Carise Deni , Brooks Adam , Alterman Arthur , McLellan A. Thomas , Hoover Valerie , Forman Robert
Published: July 2009

Community substance abuse treatment programs face many barriers to adopting “evidence-based” therapies. Training budgets are inadequate to permit acquisition of complex skills, there is little clinical supervision available, and almost all counseling is done in group sessions. The authors adopted an approach widely used in the teaching field—developing a resource “toolkit” for a specific topic, in this case, a Decisional Balance exercise often used in the evidence-based treatment approach of Motivational Interviewing. This trial toolkit was comprised of a DVD (televised during group to illustrate the clinical concept), a laminated counselor guide (to provide guidance and talking points for the counselor during group), and some worksheets and wallet cards for patients to retain key points (see Table 1 ). A feasibility trial assessed the acceptability, and sustainability of the “Decisional Balance” concept toolkit among 26 counselors and 210 of their patients, from 6 community-based substance abuse treatment programs. The great majority of patients (97%) and all counselors (100%) reported they were satisfied with the toolkit session; 84% of patients said they would like more groups like the toolkit session. Almost all counselors (96%) were still using at least one component of the toolkit 3 months after their initial exposure with no prompting. The toolkit curriculum–based approach may be a viable and attractive way of translating core concepts from sophisticated evidence-based therapies into use by counselors within contemporary, community-based treatment programs with minimal training.
Motivational Enhancement Therapy to Increase Resident Physician Engagement in Substance Abuse Education
Authors: Hettema Jennifer E. , Sorensen James L. , Uy Manelisa , Jain Sharad
Published: July 2009

Rates of screening, brief intervention, and referral to treatment (SBIRT) for alcohol and drug use by physicians remain low, despite evidence of efficacy. Motivational enhancement therapy (MET) may be a promising means to help physicians resolve ambivalence about intervening with alcohol and drug users and take advantage of educational opportunities. In the present study, 9 internal medicine residents received brief MET prior to standard education in SBIRT. Residents’ self-reported SBIRT attitudes and behaviors were measured before the intervention and at a 5-week follow-up point. Changes in SBIRT attitudes and behaviors all occurred in the expected direction, although, due to the small sample size, none reached statistical significance. Results suggest that MET may enhance educational opportunities and lead to changes in SBIRT behavior.
Inquiries about and Initiation of Buprenorphine Treatment in an Inner-City Clinic
Authors: Cunningham Chinazo O. , Giovanniello Angela , Sacajiu Galit , Li Xuan , Brisbane Mia , Sohler Nancy L.
Published: July 2009

Despite increases in opioid dependence, availability of buprenorphine treatment remains limited. Reasons may include health center concerns about becoming overwhelmed or attracting patients who differ from the local community. This study documents inquiries about and initiation of buprenorphine treatment in an inner-city health center. From 2006–2008, we collected demographic information and subsequent treatment data for everyone who inquired about treatment. Of the 324 people who inquired, 55.6% initiated treatment. The number of inquiries increased gradually over time, and most came from local community residents (80.4%). These results may allay health center concerns, and can help planning for buprenorphine treatment.
Measuring teacher beliefs about curriculum orientations using the modified‐curriculum orientations inventory
Authors: Jenkins Sharon Billburg
Published: July 2009

Although curriculum orientations are widely discussed in educational literature, the extent to which teachers and other educational specialists in the United States hold these curriculum orientations is neither well documented nor well known. The relationships between a teacher's beliefs and the five dominant curriculum orientations (Academic Rationalism, Behavioural, Humanistic, Social Reconstruction and Cognitive Process) are unclear. Therefore, it is difficult to discuss the nature of how these curriculum orientations influence teacher choices and their execution and implementation of educational policy. This study replicated the 2002 research of Cheung and Wong in Hong Kong. A sample of 308 teachers in the United States participated. Findings indicate that the reliability and validity of the data were weak to moderate, and gender, level, subject speciality and experience influence a teacher's value of the particular curriculum orientations. The research also indicates that the construct of complementary pluralism (a strong positive relationship between the orientations of an individual teacher) does not exist with the same level of intensity for teachers in the United States. Rather, the theoretical opposition of the curriculum orientations is a practical opposition.
Sound[']s right: pupils' responses to heard poetry and the revised National Curriculum for English
Authors: Gordon John
Published: July 2009

This article considers the design of poetry within the UK National Curriculum for English, where it is conceived of primarily as a print‐based medium. With reference to curricular detail, the recent Ofsted survey of poetry teaching in schools, and to original research, it describes the role the existing curricular conception of poetry can play in influencing practice, sometimes to the detriment of listening. It posits a conception of heard poetry that makes reference both to the New London Group's term ‘lifeworld’ and to T.S. Eliot's ‘auditory imagination’, synthesising the two. It presents data arising from pupils' responses to heard poetry in the classroom, in the form of Conversation Analysis transcripts, using these to illustrate the nature of the research and its interpretive work. The article then presents a summary of the findings of the full study, concluding with their implications for curricular detail. The curricular conception of poetry, it contends, is inadequate, failing to acknowledge the oral tradition in poetry, with subsequent implications for pupils' engagement and understanding of poetry in classroom‐based poetic encounters.
Task switching and subjective duration
Authors: Wearden J. H. , O'Rourke Susan C. , Matchwick Claire , Min Zhang , Maeers Sharon
Published: July 2009

Three experiments investigated the effects of switching from a nontiming task (addition of rapidly presented digits) to estimation of the duration of short tones or visual stimuli (Experiments 1 and 2), or the production of time intervals (Experiment 3). In general, compared with trials without a task-switch, trials involving a switch resulted in shorter duration estimates, but longer productions. The difficulty of the nontiming task, and the gap between the nontiming task and the timing task, also played a role, at least in some cases. Verbal estimates were shortened more at longer stimulus durations than at shorter ones in both experiments using this method. In general, the task-switch procedure produced opposite effects to “speeding up the clock” manipulations. The data were discussed in terms of models involving internal clock switch processes, including the notions of an “attentional gate” or a “flickering switch”.
Understanding cumulative risk
Authors: McCloy Rachel , Byrne Ruth M. J. , Johnson-Laird Philip N.
Published: July 2009

This paper summarizes the theory of simple cumulative risks—for example, the risk of food poisoning from the consumption of a series of portions of tainted food. Problems concerning such risks are extraordinarily difficult for naïve individuals, and the paper explains the reasons for this difficulty. It describes how naïve individuals usually attempt to estimate cumulative risks, and it outlines a computer program that models these methods. This account predicts that estimates can be improved if problems of cumulative risk are framed so that individuals can focus on the appropriate subset of cases. The paper reports two experiments that corroborated this prediction. They also showed that whether problems are stated in terms of frequencies (80 out of 100 people got food poisoning) or in terms of percentages (80% of people got food poisoning) did not reliably affect accuracy.
A Distinct Mechanism to Achieve Efficient Signal Recognition Particle (SRP)–SRP Receptor Interaction by the Chloroplast SRP Pathway
Authors: Jaru-Ampornpan Peera , Nguyen Thang X. , Shan Shu-ou
Published: July 2009

Cotranslational protein targeting by the signal recognition particle (SRP) requires the SRP RNA, which accelerates the interaction between the SRP and SRP receptor 200-fold. This otherwise universally conserved SRP RNA is missing in the chloroplast SRP (cpSRP) pathway. Instead, the cpSRP and cpSRP receptor (cpFtsY) by themselves can interact 200-fold faster than their bacterial homologues. Here, cross-complementation analyses revealed the molecular origin underlying their efficient interaction. We found that cpFtsY is 5- to 10-fold more efficient than Escherichia coli FtsY at interacting with the GTPase domain of SRP from both chloroplast and bacteria, suggesting that cpFtsY is preorganized into a conformation more conducive to complex formation. Furthermore, the cargo-binding M-domain of cpSRP provides an additional 100-fold acceleration for the interaction between the chloroplast GTPases, functionally mimicking the effect of the SRP RNA in the cotranslational targeting pathway. The stimulatory effect of the SRP RNA or the M-domain of cpSRP is specific to the homologous SRP receptor in each pathway. These results strongly suggest that the M-domain of SRP actively communicates with the SRP and SR GTPases and that the cytosolic and chloroplast SRP pathways have evolved distinct molecular mechanisms (RNA vs. protein) to mediate this communication.
Developing Kernel and Rachis Node Induce the Trichothecene Pathway of Fusarium graminearum During Wheat Head Infection
Authors: Ilgen Peter , Hadeler Birgit , Maier Frank J. , Schäfer Wilhelm
Published: July 2009

The fungal pathogen Fusarium graminearum is the most common agent of Fusarium head blight (FHB) in small grain cereals and cob rot of maize. The threat posed by this fungus is due to a decrease in yield and, additionally, mycotoxin contamination of the harvested cereals. Among the mycotoxins, trichothecenes influence virulence of F. graminearum in a highly complex manner that is strongly host- as well as chemotype-specific. The factors inducing mycotoxin production during plant infection are still unknown. To evaluate the induction of the trichothecene pathway, the green fluorescence protein (GFP) gene was fused to the promoter of the TRI5 gene coding for the trichodiene synthase and integrated into the genome by homologous integration. The resulting mutant contains a fully functional TRI5 gene ensuring virulence on wheat and exhibits GFP driven by the endogenous TRI5 promoter. We are now able to monitor the induction of trichothecenes under real-time conditions. To localize the fungus in the plant tissue, the dsRed gene was integrated under constitutive control of the glycerol-3-phosphate dehydrogenase (gpdA) promoter. We are now able to show that, first, induction of GFP as well as trichothecene production in the reporter strain reflects TRI5 induction and trichothecene production in the wild type; second, expression of TRI5 is inducible during growth in culture; and, third, trichothecene production is not uniformly induced during the onset of infection but is tissue specific during fungal infection of wheat.
Full-Size ABC Transporters from the ABCG Subfamily in Medicago truncatula
Authors: Jasinski Michal , Banasiak Joanna , Radom Marcin , Kalitkiewicz Anna , Figlerowicz Marek
Published: July 2009

Full-size ATP-binding cassette (ABC) transporters belonging to the ABCG subfamily are unique for plants and fungi. There is growing evidence that certain of these proteins play a role in plant defense or signaling systems. As yet, a complete set of full-size ABCG protein genes has been inventoried and classified in only two plants: Arabidopsis thaliana and Oryza sativa. Recently, a domain-based clustering analysis has predicted the presence of at least 12 genes encoding such proteins in the Lotus japonicus genome. Here, we identify and classify 19 genes coding full-size ABCG proteins in Medicago truncatula, a model legume plant. We have found that the majority of these genes are expressed in roots and flowers whereas only a few are expressed in leaves. Expression of several has been induced upon pathogenic infection in both roots and leaves. ABCG messenger RNAs have been detected in root nodules forming during symbiosis of legume plants and nitrogen-fixing bacteria. The data presented provide a scaffold for further studies of the physiological function of Medicago ABCG transporters and their possible role in modulating plant–microorganism interactions.
Repeat-Induced Point Mutation (RIP) as an Alternative Mechanism of Evolution Toward Virulence in Leptosphaeria maculans
Authors: Fudal Isabelle , Ross Simon , Brun Hortense , Besnard Anne-Laure , Ermel Magali , Kuhn Marie-Line , Balesdent Marie-Hélène , Rouxel Thierry
Published: July 2009

Three avirulence genes, AvrLm1, AvrLm6, and AvrLm4-7, were recently identified in Leptosphaeria maculans and found to be localized as solo genes within large noncoding, heterochromatin-like regions mainly composed of retrotransposons, truncated and degenerated by repeat-induced point mutation (RIP). The Rlm6 resistance gene has been overcome within 3 years in outdoor experiments in France and, here, we investigate the molecular basis of evolution toward virulence at the AvrLm6 locus. A region of 235 kb was sequenced in a virulent isolate and showed the deletion of AvrLm6 and three divergent mosaics of retrotransposons. AvrLm6 was found to be absent from 66% of 70 virulent isolates, with multiple events of deletion. The sequencing of virulent alleles in 24 isolates revealed a few cases of point mutations that had created stop codons in the sequence. The most frequent mutation events, however, were RIP, leading to the modification of 4 to 9% of the bases compared with the avirulent allele and generating 2 to 4 stop codons. Thus, RIP is described for the first time as an efficient mechanism leading to virulence and the multiple patterns of mutation observed suggest that multiple RIP events could occur independently in a single field population during 1 year.
The ERECTA Receptor-Like Kinase Regulates Cell Wall–Mediated Resistance to Pathogens in Arabidopsis thaliana
Authors: Sánchez-Rodríguez Clara , Estévez José Manuel , Llorente Francisco , Hernández-Blanco Camilo , Jordá Lucía , Pagán Israel , Berrocal Marta , Marco Yves , Somerville Shauna , Molina Antonio
Published: July 2009

Some receptor-like kinases (RLK) control plant development while others regulate immunity. The Arabidopsis ERECTA (ER) RLK regulates both biological processes. To discover specific components of ER-mediated immunity, a genetic screen was conducted to identify suppressors of erecta (ser) susceptibility to Plectosphaerella cucumerina fungus. The ser1 and ser2 mutations restored disease resistance to this pathogen to wild-type levels in the er-1 background but failed to suppress er-associated developmental phenotypes. The deposition of callose upon P. cucumerina inoculation, which was impaired in the er-1 plants, was also restored to near wild-type levels in the ser er-1 mutants. Analyses of er cell walls revealed that total neutral sugars were reduced and uronic acids increased relative to those of wild-type walls. Interestingly, in the ser er-1 walls, neutral sugars were elevated and uronic acids were reduced relative to both er-1 and wild-type plants. The cell-wall changes found in er-1 and the ser er-1 mutants are unlikely to contribute to their developmental alterations. However, they may influence disease resistance, as a positive correlation was found between uronic acids content and resistance to P. cucumerina. We propose a specific function for ER in regulating cell wall–mediated disease resistance that is distinct from its role in development.
Does Botrytis cinerea Ignore H2O2-Induced Oxidative Stress During Infection? Characterization of Botrytis Activator Protein 1
Authors: Temme Nora , Tudzynski Paul
Published: July 2009

Botrytis cinerea is a phytopathogen infecting a broad range of plants including strawberries and grapevine. During infection, the necrotrophic fungus is exposed to reactive oxygen species (ROS) released by the oxidative burst, an early plant defense reaction. B. cinerea even produces ROS itself in planta. This raises questions about how the pathogen senses and responds to the host defense reaction and which role the pathogen's oxidative stress response systems play. Functional analysis of the AP-1 transcription factor Bap1 confirmed its role as a pivotal regulator of ROS detoxification in vitro. Macroarray analysis revealed 99 H2O2-induced Bap1 target genes, of which several genes encoded ROS-degrading enzymes as well as other central components of the cellular redox status. However, Bap1 is not essential for pathogenesis. In planta analyses revealed that the Bap1 target genes were not expressed 2 days postinoculation although H2O2 was detectable, proving that the normal virulence of the Δbap1 mutant is not due to alternative regulation of the major oxidative stress response system in planta. The fungus obviously does not suffer H2O2-induced oxidative stress in planta, questioning classical ideas about the role of the oxidative burst in the infection process.
Identification of Beet necrotic yellow vein virus P25 Pathogenicity Factor–Interacting Sugar Beet Proteins That Represent Putative Virus Targets or Components of Plant Resistance
Authors: Thiel Heike , Varrelmann Mark
Published: July 2009

Beet necrotic yellow vein virus (BNYVV) induces the most important disease threatening sugar beet. The growth of partially resistant hybrids carrying monogenic dominant resistance genes stabilize yield but are unable to entirely prevent virus infection and replication. P25 is responsible for symptom development and previous studies have shown that recently occurring resistance-breaking isolates possess increased P25 variability. To better understand the viral pathogenicity factor's interplay with plant proteins and to possibly unravel the molecular basis of sugar beet antivirus resistance, P25 was applied in a yeast two-hybrid screen of a resistant sugar beet cDNA library. This screen identified candidate proteins recognized as orthologues from other plant species which are known to be expressed following pathogen infection and involved in plant defense response. Most of the candidates potentially related to host-pathogen interactions were involved in the ubiquitylation process and plants response to stress, and were part of cell and metabolism components. The interaction of several candidate genes with P25 was confirmed in Nicotiana benthamiana leaf cells by transient agrobacterium-mediated expression applying bimolecular fluorescence complementation assay. The putative functions of several of the candidates identified support previous findings and present first targets for understanding the BNYVV pathogenicity and antivirus resistance mechanism.
Complete Genome Sequence of Citrus Huanglongbing Bacterium, ‘CandidatusLiberibacter asiaticus’ Obtained Through Metagenomics
Authors: Duan Yongping , Zhou Lijuan , Hall David G. , Li Wenbin , Doddapaneni Harshavardhan , Lin Hong , Liu Li , Vahling Cheryl M. , Gabriel Dean W. , Williams Kelly P. , Dickerman Allan , Sun Yijun , Gottwald Tim
Published: July 2009

Citrus huanglongbing is the most destructive disease of citrus worldwide. It is spread by citrus psyllids and is associated with a low-titer, phloem-limited infection by any of three uncultured species of α-Proteobacteria, ‘Candidatus Liberibacter asiaticus’, ‘Ca. L. americanus’, and ‘Ca. L. africanus’. A complete circular ‘Ca. L. asiaticus’ genome has been obtained by metagenomics, using the DNA extracted from a single ‘Ca. L. asiaticus’–infected psyllid. The 1.23-Mb genome has an average 36.5% GC content. Annotation revealed a high percentage of genes involved in both cell motility (4.5%) and active transport in general (8.0%), which may contribute to its virulence. ‘Ca. L. asiaticus’ appears to have a limited ability for aerobic respiration and is likely auxotrophic for at least five amino acids. Consistent with its intracellular nature, ‘Ca. L. asiaticus’ lacks type III and type IV secretion systems as well as typical free-living or plant-colonizing extracellular degradative enzymes. ‘Ca. L. asiaticus’ appears to have all type I secretion system genes needed for both multidrug efflux and toxin effector secretion. Multi-protein phylogenetic analysis confirmed ‘Ca. L. asiaticus’ as an early-branching and highly divergent member of the family Rhizobiaceae. This is the first genome sequence of an uncultured α-proteobacteria that is both an intracellular plant pathogen and insect symbiont.
The ThPG1 Endopolygalacturonase Is Required for theTrichoderma harzianum–Plant Beneficial Interaction
Authors: Morán-Diez Eugenia , Hermosa Rosa , Ambrosino Patrizia , Cardoza Rosa E. , Gutiérrez Santiago , Lorito Matteo , Monte Enrique
Published: July 2009

Considering the complexity of the in vivo interactions established by a mycoparasitic biocontrol agent at the plant rhizosphere, proteomic, genomic, and transcriptomic approaches were used to study a novel Trichoderma gene coding for a plant cell wall (PCW)-degrading enzyme. A proteome analysis, using a three-component (Trichoderma spp.–tomato plantlets–pathogen) system, allowed us to identify a differentially expressed Trichoderma harzianum endopolygalacturonase (endoPG). Spot 0303 remarkably increased only in the presence of the soilborne pathogens Rhizoctonia solani and Pythium ultimum, and corresponded to an expressed sequence tag from a T. harzianum T34 cDNA library that was constructed in the presence of PCW polymers and used to isolate the Thpg1 gene. Compared with the wild-type strain, Thpg1-silenced transformants showed lower PG activity, less growth on pectin medium, and reduced capability to colonize tomato roots. These results were combined with microarray comparative data from the transcriptome of Arabidopsis plants inoculated with the wild type or a Thpg1-silenced transformant (ePG5). The endoPG-encoding gene was found to be required for active root colonization and plant defense induction by T. harzianum T34. In vivo assays showed that Botrytis cinerea leaf necrotic lesions were slightly smaller in plants colonized by ePG5, although no statistically significant differences were observed.
Impact of Early Spring Weather Factors on the Risk of Tomato Spotted Wilt in Peanut
Authors: Olatinwo R. O. , Paz J. O. , Brown S. L. , Kemerait R. C. , Culbreath A. K. , Hoogenboom G.
Published: July 2009

Peanut growers in the southeastern United States have suffered significant economic losses due to spotted wilt caused by Tomato spotted wilt virus (TSWV). The virus is transmitted by western flower thrips, Frankliniella occidentalis, and tobacco thrips, F. fusca, and was first reported in the southeast in 1986. The severity of this disease is extremely variable in individual peanut fields, perhaps due to the sensitivity of the vector population to changing weather patterns. The objective of this study was to investigate the impact of early spring weather on spotted wilt risk in peanut. On-farm surveys of spotted wilt severity were conducted in Georgia peanut fields in 1998, 1999, 2002, 2004, and 2005. The percent spotted wilt intensity (%) for cv. Georgia Green was recorded and categorized into three intensity levels: low, moderate, and high. Meteorological data were obtained from the Georgia Automated Environmental Monitoring Network for the period between March 1 and April 30. Statistical analysis was conducted to identify weather variables that had significant impact on spotted wilt intensity. The results indicated a high probability of spotted wilt if the number of rain days during March was greater than or equal to 10 days and planting was before 11 May or after 5 June. The total evapotranspiration in April (>127 mm) and the average daily minimum temperature in March (>6.8°C) similarly increased the risk of spotted wilt. Knowing in advance the level of spotted wilt risk expected in a peanut field could assist growers with evaluating management options and significantly improve the impact of their decisions against spotted wilt risk in peanut.
Erysiphe trifolii Causing Powdery Mildew of Lentil (Lens culinaris)
Authors: Attanayake Renuka N. , Glawe Dean A. , Dugan Frank M. , Chen Weidong
Published: July 2009

The taxonomy of the powdery mildew fungus infecting lentil in the Pacific Northwest (PNW) of the United States was investigated on the basis of morphology and rDNA internal transcribed spacer (ITS) sequences. Anamorphic characters were in close agreement with descriptions of Erysiphe trifolii. However, teleomorphs formed chasmothecial appendages with highly branched apices, whereas E. trifolii has been described as producing flexuous or sometimes loosely branched appendages. Branched appendages have been described in Erysiphe diffusa, a fungus reported from species of Lens, Glycine, and Sophora, raising the possibility that the PNW fungus could be E. diffusa. Examination of morphological characters of an authentic specimen of E. trifolii from Austria determined that it included chasmothecial appendages resembling those seen in PNW specimens. Furthermore, ITS sequences from five powdery mildew samples collected from lentils in PNW greenhouses and fields from 2006 to 2008 were identical to one another, and exhibited higher similarity to sequences of E. trifolii (99%) than to those of any other Erysiphe spp. available in GenBank. Parsimony analysis grouped the lentil powdery mildew into a clade with Erysiphe baeumleri, E. trifolii, and E. trifolii–like Oidium sp., but indicated a more distant relationship to E. diffusa. In greenhouse inoculation studies, the lentil powdery mildew fungus did not infect soybean genotypes known to be susceptible to E. diffusa. The pathogenicity of E. trifolii on lentil was confirmed using modified Koch's postulates. This is the first report of E. trifolii infecting lentil. E. diffusa and E. trifolii have different host ranges, so the discovery of E. trifolii on lentil has implications both for determining species of powdery mildews on cool-season grain legumes, and in disease management.
Curative and Protectant Activity of Fungicides for Control of Crown Rot of Strawberry Caused by Colletotrichum gloeosporioides
Authors: MacKenzie S. J. , Mertely J. C. , Peres N. A.
Published: July 2009

The ability of fungicides to control Colletotrichum crown rot of strawberry caused by C. gloeosporioides was examined over three seasons. A single application of each fungicide was made 2 days before inoculation (2 DBI) or 1 day after inoculation (1 DAI) with conidial suspensions of C. gloeosporioides. The proportion of plants collapsed on one date at the end of each season was evaluated. In a combined analysis, there was a significant fungicide treatment-season interaction (P = 0.004). Percent mortality was 64% over 3 years in control plots that were inoculated with C. gloeosporioides but not treated with fungicide. Captan applied 2 DBI consistently reduced plant mortality (mean mortality = 17%). However, it was not as effective when applied 1 DAI (mean mortality = 46%). Azoxystrobin, pyraclostrobin, and thiophanate-methyl all reduced plant mortality relative to the control if applied 2 DBI (mean mortality = 46% for azoxystrobin, 37% for pyraclostrobin, and 41% for thiophanate-methyl) or 1 DAI (mean mortality = 29% for azoxystrobin, 27% for pyraclostrobin, and 32% for thiophanate-methyl). Results indicated that these fungicides were more effective when applied 1 DAI; however, lower plant mortality was not always observed with postinoculation applications. Cyprodinil + fludioxonil reduced mortality relative to the control, but there was no consistent evidence that it was more effective when applied at 2 DBI (mean mortality = 39%) than when applied 1 DAI (mean mortality = 40%). Similarly, mortality in plots treated with thiram 2 DBI (mean mortality = 30%) or 1 DAI (mean mortality = 32%) was not different. Potassium phosphite did not affect mortality, regardless of the timing of application (2 DBI mean mortality = 61%, 1 DAI mean mortality = 67%). The results indicated that an effective strategy for controlling Colletotrichum crown rot caused by C. gloeosporioides should be based on weekly applications of captan throughout the growing season. Azoxystrobin, pyraclostrobin, or thiophanate-methyl applications should be applied when weather conditions are highly favorable for disease development and the activity of contact fungicides such as captan or thiram might be compromised.