9448035
Shifting fungal reproductive mode by manipulation of mating type genes: obligatory heterothallism of Gibberella zeae.
Fungi capable of sexual reproduction use heterothallic (self-sterile) or homothallic (self-fertile) mating strategies. In most ascomycetes, a single mating type locus, MAT, with two alternative forms (MAT1-1 and MAT1-2) called idiomorphs, controls mating ability. In heterothallic ascomycetes, these alternative idiomorphs reside in different nuclei. In contrast, most homothallic ascomycetes carry both MAT1-1 and MAT1-2 in a single nucleus, usually closely linked. An example of the latter is Gibberella zeae, a species that is capable of both selfing and outcrossing. G. zeae is a devastating cereal pathogen of ubiquitous geographical distribution, and also a producer of mycotoxins that threaten human and animal health. We asked whether G. zeae could be made strictly heterothallic by manipulation of MAT. Targeted gene replacement was used to differentially delete MAT1-1 or MAT1-2 from a wild-type haploid MAT1-1; MAT1-2 strain, resulting in MAT1-1; mat1-2, mat1-1; MAT1-2 strains that were self-sterile, yet able to cross to wild-type testers and, more importantly, to each other. These results indicated that differential deletion of MAT idiomorphs eliminates selfing ability of G. zeae, but the ability to outcross is retained. They also indicated that both MAT idiomorphs are required for self-fertility. To our knowledge, this is the first report of complete conversion of fungal reproductive strategy from homothallic to heterothallic by targeted manipulation of MAT. Practically, this approach opens the door to simple and efficient procedures for obtaining sexual recombinants of G. zeae that will be useful for genetic analyses of pathogenicity and other traits, such as the ability to produce mycotoxins.
42681890
Genetic diversity and fitness of Fusarium graminearum populations from rice in Korea.
Fusarium graminearum is an important fungal pathogen of cereal crops and produces mycotoxins, such as the trichothecenes nivalenol and deoxynivalenol. This species may be subdivided into a series of genetic lineages or phylogenetic species. We identified strains of F. graminearum from the Republic of Korea to lineage, tested their ability to produce nivalenol and deoxynivalenol, and determined the genetic composition and structure of the populations from which they were recovered. Based on amplified fragment length polymorphism (AFLP), PCR genotyping, and chemical analyses of trichothecenes, all 249 isolates from southern provinces belonged to lineage 6, with 241 having the nivalenol genotype and 8 having the deoxynivalenol genotype. In the eastern Korea province, we recovered 84 lineage 6 isolates with the nivalenol genotype and 23 lineage 7 isolates with the deoxynivalenol genotype. Among 333 lineage 6 isolates, 36% of the AFLP bands were polymorphic, and there were 270 multilocus haplotypes. Genetic identity among populations was high (>0.972), and genotype diversity was low (30 to 58%). To test the adaptation of lineage 6 to rice, conidial mixtures of strains from lineages 3, 6, and 7 were inoculated onto rice plants and then recovered from the rice grains produced. Strains representing lineages 6 and 7 were recovered from inoculated spikelets at similar frequencies that were much higher than those for the strain representing lineage 3. Abundant perithecia were produced on rice straw, and 247 single-ascospore isolates were recovered from 247 perithecia. Perithecia representing lineage 6 (87%) were the most common, followed by those representing lineage 7 (13%), with perithecia representing lineage 3 not detected. These results suggest that F. graminearum lineage 6 may have a host preference for rice and that it may be more fit in a rice agroecosystem than are the other lineages present in Korea.
23566647
Development of a conditional gene expression system using a zearalenone-inducible promoter for the ascomycete fungus Gibberella zeae.
The ascomycete fungus Gibberella zeae is an important plant pathogen that causes fusarium head blight on small grains. Molecular studies of this fungus have been performed extensively to uncover the biological mechanisms related to pathogenicity, toxin production, and sexual reproduction. Molecular methods, such as targeted gene deletion, gene overexpression, and gene fusion to green fluorescent protein (GFP), are relatively easy to perform with this fungus; however, conditional expression systems have not been developed. The purpose of this study was to identify a promoter that could be induced by zearalenone (ZEA) for the development of a conditional expression system in G. zeae. Through microarray analysis, we isolated one zearalenone response gene (ZEAR) whose expression was increased more than 50 times after ZEA treatment. Northern blot analysis showed that the ZEAR transcript dramatically increased after 1 h of ZEA treatment. To determine the utility of the ZEAR promoter, called Pzear, in a conditional expression system, we transformed a Pzear::GFP fusion construct into G. zeae. Our data showed a ZEA concentration-dependent increase in GFP expression. We also replaced the promoter of G. zeae metE (GzmetE), an essential gene for methionine biosynthesis, with the Pzear promoter. The growth of the Pzear-GzmetE mutant on minimal medium was dependent on the ZEA concentration supplemented in the medium and showed that GzMetE expression was induced by ZEA. This study is the first report of an inducible promoter in G. zeae. Our system will be useful for the characterization of essential gene functions in this fungus through differential and ZEA-dependent gene expression. In addition, the Pzear promoter may be applicable as a biosensor for the detection of ZEA contamination in agricultural products.
19885934
Identification and functional characterization of genes involved in the sexual reproduction of the ascomycete fungus Gibberella zeae.
We previously reported that G protein alpha subunit 1 (GPA1) is essential for sexual reproduction in the homothallic ascomycete fungus Gibberella zeae. In this study we performed microarray analyses on a GPA1 deletion mutant of G. zeae (Δgpa1) to identify genes involved in the sexual reproduction of this fungus. In the Δgpa1 strain, 645 genes were down-regulated and 550 genes were up-regulated during sexual reproduction when compared to the wild-type strain. One hundred of the down-regulated genes were selected for further investigation based on orthologous group clusters and differences in transcript levels. Quantitative real time-PCR was used to determine transcriptional profiles of these genes at various sexual and vegetative stages. We observed that transcript levels of 78 of these genes were dramatically increased in the wild-type strain during sexual reproduction compared to levels observed during vegetative growth, and were down-regulated in Δgpa1 compared to the wild-type strain. We deleted 57 of these genes and found that four of the deletion mutants lost self-fertility and five produced fewer perithecia compared to the wild-type strain. Two mutants produced wild-type numbers of perithecia, but maturation of perithecia and ascospores was delayed. In all we identified 11 genes that are involved in sexual reproduction of G. zeae and present evidence that some of these genes function at distinct stages during sexual reproduction in the fungus.
23509495
FgVelB globally regulates sexual reproduction, mycotoxin production and pathogenicity in the cereal pathogen Fusarium graminearum.
The velvet genes are conserved in ascomycetous fungi and function as global regulators of differentiation and secondary metabolism. Here, we characterized one of the velvet genes, designated FgVelB, in the plant-pathogenic fungus Fusarium graminearum, which causes fusarium head blight in cereals and produces mycotoxins within plants. FgVelB-deleted (ΔFgVelB) strains produced fewer aerial mycelia with less pigmentation than those of the wild-type (WT) during vegetative growth. Under sexual development conditions, the ΔFgVelB strains produced no fruiting bodies but retained male fertility, and conidiation was threefold higher compared with the WT strain. Production of trichothecene and zearalenone was dramatically reduced compared with the WT strain. In addition, the ΔFgVelB strains were incapable of colonizing host plant tissues. Transcript analyses revealed that FgVelB was highly expressed during the sexual development stage, and may be regulated by a mitogen-activated protein kinase cascade. Microarray analysis showed that FgVelB affects regulatory pathways mediated by the mating-type loci and a G-protein alpha subunit, as well as primary and secondary metabolism. These results suggest that FgVelB has diverse biological functions, probably by acting as a member of a possible velvet protein complex, although identification of the FgVelB-FgVeA complex and the determination of its roles require further investigation.
24325594
Population structure of and mycotoxin production by Fusarium graminearum from maize in South Korea.
Fusarium graminearum (Gibberella zeae) is an important pathogen of wheat, maize, barley, and rice in South Korea, and harvested grain often is contaminated with trichothecenes such as deoxynivalenol and nivalenol. In this study, we examined 568 isolates of F. graminearum collected from maize at eight locations in South Korea. We used amplified fragment length polymorphisms (AFLPs) to identify four lineages (2, 3, 6, and 7); lineage 7 was the most common (75%), followed by lineage 6 (12%), lineage 3 (12%), and lineage 2 (1%). The genetic identity among populations was high (>0.98), and the effective migration rate between locations was higher than that between lineages. Female fertility varied by lineage: all lineage 7 isolates were fertile, while 70%, 26%, and 14% of the isolates in lineages 6, 3, and 2, respectively, were fertile. All lineage 3 and lineage 7 isolates produced deoxynivalenol, whereas most lineage 2 and 6 isolates produced nivalenol. Genotypic diversity in lineage 3 and lineage 6 populations is similar to that found in previously described Korean rice populations, but genotypic diversity in lineage 7 is much lower, even though similar levels of gene flow occur between lineage 7 populations. We conclude that lineage 7 was relatively recently introduced into South Korea, perhaps accompanying imported maize seeds.
15872751
Human Genomic Deletions Generated by SVA-Associated Events
Mobile elements are responsible for half of the human genome. Among the elements, L1 and Alu are most ubiquitous. They use L1 enzymatic machinery to move in their host genomes. A significant amount of research has been conducted about these two elements. The results showed that these two elements have played important roles in generating genomic variations between human and chimpanzee lineages and even within a species, through various mechanisms. SVA elements are a third type of mobile element which uses the L1 enzymatic machinery to propagate in the human genome but has not been studied much relative to the other elements. Here, we attempt the first identification of the human genomic deletions caused by SVA elements, through the comparison of human and chimpanzee genome sequences. We identified 13 SVA recombination-associated deletions (SRADs) and 13 SVA insertion-mediated deletions (SIMDs) in the human genome and characterized them, focusing on deletion size and the mechanisms causing the events. The results showed that the SRADs and SIMDs have deleted 15,752 and 30,785 bp, respectively, in the human genome since the divergence of human and chimpanzee and that SRADs were caused by two different mechanisms, nonhomologous end joining and nonallelic homologous recombination.
23818831
The critical-size supraalveolar peri-implant defect model: reproducibility in histometric data acquisition of alveolar bone formation and osseointegration.
OBJECTIVE
The objective of this report is to present the reproducibility of outcomes assessments in the Critical-Size Supraalveolar Peri-Implant Defect Model.


MATERIALS AND METHODS
Two examiners without specific experience in histological analysis and one experienced examiner performed the histometric evaluation. A comprehensive training program in data acquisition and histological analysis was established, the inexperienced examiners underwent approximately 12 h of training over multiple sessions. A custom-designed image analysis software macro and a computer-based image system were used to analyse digital images generated by a microscope camera system. Nine parameters for newly formed and resident bone were evaluated. Examiners performed histometric analysis using 36 histologic sections selected from critical-size supraalveolar peri-implant defects in 12 male Hound Labrador Mongrel dogs. Buccal and lingual measurements were performed in 72 sites. Intra- and inter-examiner reproducibility were evaluated using the concordance correlation coefficient (CCC) and means +/- SD of the differences. Systematic errors were evaluated using an F-test for equality of means and variances.


RESULTS
Intra-examiner reproducibility was high for all parameters evaluated, the lowest CCC observed being 0.87. Inter-examiner reproducibility was also high, most CCCs exceeding 0.90. Minor systematic errors for intra- and inter-examiner comparisons were occasionally observed. The results imply a high temporal stability because recordings were performed 3 months apart. Measurement errors were stable throughout the range of observations for all parameters.


CONCLUSIONS
High examiner reproducibility and temporal stability can be achieved for histometric data acquisition using the Critical-Size Supraalveolar Peri-Implant Defect Model. Examiner reproducibility should be routinely assessed, reported, and accounted for to assure the quality of evidence generated by preclinical studies.
843660
Different evolutionary fates of recently integrated human and chimpanzee LINE-1 retrotransposons.
The long interspersed element-1 (LINE-1 or L1) is a highly successful retrotransposon in mammals. L1 elements have continued to actively propagate subsequent to the human-chimpanzee divergence, approximately 6 million years ago, resulting in species-specific inserts. Here, we report a detailed characterization of chimpanzee-specific L1 subfamily diversity and a comparison with their human-specific counterparts. Our results indicate that L1 elements have experienced different evolutionary fates in humans and chimpanzees within the past approximately 6 million years. Although the species-specific L1 copy numbers are on the same order in both species (1200-2000 copies), the number of retrotransposition-competent elements appears to be much higher in the human genome than in the chimpanzee genome. Also, while human L1 subfamilies belong to the same lineage, we identified two lineages of recently integrated L1 subfamilies in the chimpanzee genome. The two lineages seem to have coexisted for several million years, but only one shows evidence of expansion within the past three million years. These differential evolutionary paths may be the result of random variation, or the product of competition between L1 subfamily lineages. Our results suggest that the coexistence of several L1 subfamily lineages within a species may be resolved in a very short evolutionary period of time, perhaps in just a few million years. Therefore, the chimpanzee genome constitutes an excellent model in which to analyze the evolutionary dynamics of L1 retrotransposons.
7545804
Oregon 'Pinot noir' grape anthocyanin enhancement by early leaf removal.
Complete cluster zone leaf removal of 'Pinot noir' was initiated at three separate pre-véraison growth stages (bloom, grain-pea size, and bunch closure) and maintained leaf free until harvest, for four growing seasons (2008-2011). Fruit anthocyanin composition was examined at harvest for the last two vintages (2010 and 2011) and compared to a control-no cluster zone leaf removal. Experiments were conducted at two commercially operating Oregon vineyards (site A=420 rootstock/'Pinot noir' 115 scion and site B=3309C rootstock/'Pinot noir' 777 scion). All clusters contained the five anthocyanins typically found in 'Pinot noir'. Leaf removal at bloom and maintained until harvest produced maximum anthocyanin accumulation in 'Pinot noir' grapes (site A=85.24 mg/100 g and site B=125.06 mg/100 g), compared to no leaf removal (control; site A=57.91 mg/100 g and site B=97.56 mg/100 g). Even leaf removal at bunch closure (last leaf removal initiation period) increased grape anthocyanin (site A=73.22 mg/100 g and site B=118.93 mg/100 g) compared to control, but total anthocyanins were lower than grapes from bloom leaf removal (first time period). Results differed slightly by vineyard site and rootstock/scion combination.
21143386
Rational design, synthesis, and biological evaluation of progesterone-modified MRI contrast agents.
A series of contrast agents for magnetic resonance imaging (MRI) aimed at noninvasively determining the hormone receptor status of cancer in vitro was developed. These MRI contrast agents were prepared by conjugating progesterone to clinically used Gd(III) chelates. These agents exhibited higher progesterone receptor binding affinities in the nanomolar range and intracellular accumulation. High logP values of the modified compounds suggested that the lipophilicity of the steroid conjugates may have contributed to membrane permeability. Synchrotron radiation X-ray fluorescence microscopy and magnetic resonance images revealed that the synthesized conjugates showed the greatest cellular accumulation and significant increase in relaxivity in vitro compared to the previously developed steroid-modified agent. Transcriptional assays using the progesterone response element linked to luciferase indicated that the contrast agents entered the cell, interacted with the biological target, and drove specific progesterone-mediated transcription.