bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light-Regulated, Tissue-Specific, and Cell Differentiation-Specific Expression of the Arabidopsis Fe(III)-Chelate Reductase Gene AtFRO6
Authors: Feng Haizhong , An Fengying , Zhang Suzhi , Ji Zhendong , Ling Hong-Qing , Zuo Jianru 
Published: February 2006

Abstract
Iron is an essential element for almost all living organisms, actively involved in a variety of cellular activities. To acquire iron from soil, strategy I plants such as Arabidopsis (Arabidopsis thaliana) must first reduce ferric to ferrous iron by Fe(III)-chelate reductases (FROs). FRO genes display distinctive expression patterns in several plant species. However, regulation of FRO genes is not well understood. Here, we report a systematic characterization of the AtFRO6 expression during plant growth and development. AtFRO6, encoding a putative FRO, is specifically expressed in green-aerial tissues in a light-dependent manner. Analysis of mutant promoter-β-glucuronidase reporter genes in transgenic Arabidopsis plants revealed the presence of multiple light-responsive elements in the AtFRO6 promoter. These light-responsive elements may act synergistically to confer light responsiveness to the AtFRO6 promoter. Moreover, no AtFRO6 expression was detected in dedifferentiated green calli of the korrigan1-2 (kor1-2) mutant or undifferentiated calli derived from wild-type explants. Conversely, AtFRO6 is expressed in redifferentiated kor1-2 shoot-like structures and differentiating calli of wild-type explants. In addition, AtFRO7, but not AtFRO5 and AtFRO8, also shows a reduced expression level in kor1-2 green calli. These results suggest that whereas photosynthesis is necessary but not sufficient, both light and cell differentiation are necessary for AtFRO6 expression. We propose that AtFRO6 expression is light regulated in a tissue- or cell differentiation-specific manner to facilitate the acquisition of iron in response to distinctive developmental cues.
Gain-of-Function Phenotypes of Many CLAVATA3/ESR Genes, Including Four New Family Members, Correlate with Tandem Variations in the Conserved CLAVATA3/ESR Domain
Authors: Strabala Timothy J. , O'Donnell Philip J. , Smit Anne-Marie , Ampomah-Dwamena Charles , Martin E. Jane , Netzler Natalie , Nieuwenhuizen Niels J. , Quinn Brian D. , Foote Humphrey C.C. , Hudson Keith R. 
Published: February 2006

Abstract
Secreted peptide ligands are known to play key roles in the regulation of plant growth, development, and environmental responses. However, phenotypes for surprisingly few such genes have been identified via loss-of-function mutant screens. To begin to understand the processes regulated by the CLAVATA3 (CLV3)/ESR (CLE) ligand gene family, we took a systems approach to gene identification and gain-of-function phenotype screens in transgenic plants. We identified four new CLE family members in the Arabidopsis (Arabidopsis thaliana) genome sequence and determined their relative transcript levels in various organs. Overexpression of CLV3 and the 17 CLE genes we tested resulted in premature mortality and/or developmental timing delays in transgenic Arabidopsis plants. Overexpression of 10 CLE genes and the CLV3 positive control resulted in arrest of growth from the shoot apical meristem (SAM). Overexpression of nearly all the CLE genes and CLV3 resulted in either inhibition or stimulation of root growth. CLE4 expression reversed the SAM proliferation phenotype of a clv3 mutant to one of SAM arrest. Dwarf plants resulted from overexpression of five CLE genes. Overexpression of new family members CLE42 and CLE44 resulted in distinctive shrub-like dwarf plants lacking apical dominance. Our results indicate the capacity for functional redundancy of many of the CLE ligands. Additionally, overexpression phenotypes of various CLE family members suggest roles in organ size regulation, apical dominance, and root growth. Similarities among overexpression phenotypes of many CLE genes correlate with similarities in their CLE domain sequences, suggesting that the CLE domain is responsible for interaction with cognate receptors.
Ethylene Modulates Flavonoid Accumulation and Gravitropic Responses in Roots of Arabidopsis
Authors: Buer Charles S. , Sukumar Poornima , Muday Gloria K. 
Published: February 2006

AbstractPlant organs change their growth direction in response to reorientation relative to the gravity vector. We explored the role of ethylene in Arabidopsis (Arabidopsis thaliana) root gravitropism. Treatment of wild-type Columbia seedlings with the ethylene precursor 1-aminocyclopropane carboxylic acid (ACC) reduced root elongation and gravitropic curvature. The ethylene-insensitive mutants ein2-5 and etr1-3 had wild-type root gravity responses, but lacked the growth and gravity inhibition by ACC found in the wild type. We examined the effect of ACC on tt4(2YY6) seedlings, which have a null mutation in the gene encoding chalcone synthase, the first enzyme in flavonoid synthesis. The tt4(2YY6) mutant makes no flavonoids, has elevated indole-3-acetic acid transport, and exhibits a delayed gravity response. Roots of tt4(2YY6), the backcrossed line tt4-2, and two other tt4 alleles had wild-type sensitivity to growth inhibition by ACC, whereas the root gravitropic curvature of these tt4 alleles was much less inhibited by ACC than wild-type roots, suggesting that ACC may reduce gravitropic curvature by altering flavonoid synthesis. ACC treatment induced flavonoid accumulation in root tips, as judged by a dye that becomes fluorescent upon binding flavonoids in wild type, but not in ein2-5 and etr1-3. ACC also prevented a transient peak in flavonoid synthesis in response to gravity. Together, these experiments suggest that elevated ethylene levels negatively regulate root gravitropism, using EIN2- and ETR1-dependent pathways, and that ACC inhibition of gravity response occurs through altering flavonoid synthesis.
Defective Long-Distance Auxin Transport Regulation in the Medicago truncatula super numeric nodules Mutant
Authors: van Noorden Giel E. , Ross John J. , Reid James B. , Rolfe Barry G. , Mathesius Ulrike 
Published: February 2006

Abstract
Long-distance auxin transport was examined in Medicago truncatula and in its supernodulating mutant sunn (super numeric nodules) to investigate the regulation of auxin transport during autoregulation of nodulation (AON). A method was developed to monitor the transport of auxin from the shoot to the root in whole seedlings. Subsequently, the transport was monitored after inoculation of roots with the nodulating symbiont Sinorhizobium meliloti. The sunn mutant showed an increased amount of auxin transported from the shoot to the root compared to the wild type. The auxin transport capacity of excised root segments was similar in wild type and sunn, suggesting that the difference in long-distance auxin transfer between them is due to loading in the shoot. After inoculation, wild-type seedlings showed decreased auxin loading from the shoot to the root; however, the sunn mutant failed to reduce the amount of auxin loaded. The time of reduced auxin loading correlated with the onset of AON. Quantification of endogenous auxin levels at the site of nodule initiation showed that sunn contained three times more auxin than wild type. Inoculation of sunn failed to reduce the level of auxin within 24 h, as was observed in the wild type. We propose a model for the role of auxin during AON of indeterminate legumes: 1) high levels of endogenous auxin are correlated with increased numbers of nodules, 2) inoculation of roots reduces auxin loading from the shoot to the root, and 3) subsequent reduction of auxin levels in the root inhibits further nodule initiation.
A Transcriptome-Based Characterization of Habituation in Plant Tissue Culture
Authors: Pischke Melissa S. , Huttlin Edward L. , Hegeman Adrian D. , Sussman Michael R. 
Published: February 2006

Abstract
For the last 50 years, scientists have recognized that varying ratios of the plant hormones cytokinin and auxin induce plant cells to form particular tissues: undifferentiated calli, shoot structures, root structures, or a whole plant. Proliferation of undifferentiated callus tissue, greening, and the formation of shoot structures are all cytokinin-dependent processes. Habituation refers to a naturally occurring phenomenon whereby callus cultures, upon continued passage, lose their requirement for cytokinin. Earlier studies of calli with a higher-than-normal cytokinin content indicate that overproduction of cytokinin by the culture tissues is a possible explanation for this acquired cytokinin independence. A transcriptome-based analysis of a well established habituated Arabidopsis (Arabidopsis thaliana) cell culture line was undertaken, to explore genome-wide expression changes underlying the phenomenon of habituation. Increased levels of expression of the cytokinin receptor CRE1, as well as altered levels of expression of several other genes involved in cytokinin signaling, indicated that naturally acquired deregulation of cytokinin-signaling components could play a previously unrecognized role in habituation. Up-regulation of several cytokinin oxidases, down-regulation of several known cytokinin-inducible genes, and a lack of regulation of the cytokinin synthases indicated that increases in hormone concentration may not be required for habituation. In addition, up-regulation of the homeodomain transcription factor FWA, transposon-related elements, and several DNA- and chromatin-modifying enzymes indicated that epigenetic changes contribute to the acquisition of cytokinin habituation.
Cytoplasmic Male Sterility of Rice with Boro II Cytoplasm Is Caused by a Cytotoxic Peptide and Is Restored by Two Related PPR Motif Genes via Distinct Modes of mRNA Silencing
Authors: Wang Zhonghua , Zou Yanjiao , Li Xiaoyu , Zhang Qunyu , Chen Letian , Wu Hao , Su Dihua , Chen Yuanling , Guo Jingxin , Luo Da , Long Yunming , Zhong Yang , Liu Yao-Guang 
Published: February 2006

AbstractCytoplasmic male sterility (CMS) and nucleus-controlled fertility restoration are widespread plant reproductive features that provide useful tools to exploit heterosis in crops. However, the molecular mechanism underlying this kind of cytoplasmic–nuclear interaction remains unclear. Here, we show in rice (Oryza sativa) with Boro II cytoplasm that an abnormal mitochondrial open reading frame, orf79, is cotranscribed with a duplicated atp6 (B-atp6) gene and encodes a cytotoxic peptide. Expression of orf79 in CMS lines and transgenic rice plants caused gametophytic male sterility. Immunoblot analysis showed that the ORF79 protein accumulates specifically in microspores. Two fertility restorer genes, Rf1a and Rf1b, were identified at the classical locus Rf-1 as members of a multigene cluster that encode pentatricopeptide repeat proteins. RF1A and RF1B are both targeted to mitochondria and can restore male fertility by blocking ORF79 production via endonucleolytic cleavage (RF1A) or degradation (RF1B) of dicistronic B-atp6/orf79 mRNA. In the presence of both restorers, RF1A was epistatic over RF1B in the mRNA processing. We have also shown that RF1A plays an additional role in promoting the editing of atp6 mRNAs, independent of its cleavage function.
TheArabidopsisAux/IAA Protein Family Has Diversified in Degradation and Auxin Responsiveness
Authors: Dreher Kate A. , Brown Jessica , Saw Robert E. , Callis Judy 
Published: February 2006

AbstractRapid, auxin-responsive degradation of multiple auxin/indole-3-acetic acid (Aux/IAA) proteins is essential for plant growth and development. Domain II residues were previously shown to be required for the degradation of several Arabidopsis thaliana Aux/IAA proteins. We examined the degradation of additional full-length family members and the proteolytic importance of N-terminal residues outside domain II using luciferase (LUC) fusions. Elimination of domain I did not affect degradation. However, substituting an Arg for a conserved Lys between domains I and II specifically impaired basal degradation without compromising the auxin-mediated acceleration of degradation. IAA8, IAA9, and IAA28 contain domain II and a conserved Lys, but they were degraded more slowly than previously characterized family members when expressed as LUC fusions, suggesting that sequences outside domain II influence proteolysis. We analyzed the degradation of IAA31, with a region somewhat similar to domain II but without the conserved Lys, and of IAA20, which lacks domain II and the conserved Lys. Both IAA20:LUC and epitope-tagged IAA20 were long-lived, and their longevity was not influenced by auxin. Epitope-tagged IAA31 was long-lived, like IAA20, but by contrast, it showed accelerated degradation in response to auxin. The existence of long-lived and auxin-insensitive Aux/IAA proteins suggeststhat they may play a novel role in auxin signaling.
Arabidopsis GLUTAMINE-RICH PROTEIN23Is Essential for Early Embryogenesis and Encodes a Novel Nuclear PPR Motif Protein That Interacts with RNA Polymerase II Subunit III
Authors: Ding Yong-He , Liu Nai-You , Tang Zuo-Shun , Liu Jie , Yang Wei-Cai 
Published: February 2006

AbstractPrecise control of gene expression is critical for embryo development in both animals and plants. We report that Arabidopsis thaliana GLUTAMINE-RICH PROTEIN23 (GRP23) is a pentatricopeptide repeat (PPR) protein that functions as a potential regulator of gene expression during early embryogenesis in Arabidopsis. Loss-of-function mutations of GRP23 caused the arrest of early embryo development. The vast majority of the mutant embryos arrested before the 16-cell dermatogen stage, and none of the grp23 embryos reached the heart stage. In addition, 19% of the mutant embryos displayed aberrant cell division patterns. GRP23 encodes a polypeptide with a Leu zipper domain, nine PPRs at the N terminus, and a Gln-rich C-terminal domain with an unusual WQQ repeat. GRP23 is a nuclear protein that physically interacts with RNA polymerase II subunit III in both yeast and plant cells. GRP23 is expressed in developing embryos up to the heart stage, as revealed by β-glucuronidase reporter gene expression and RNA in situ hybridization. Together, our data suggest that GRP23, by interaction with RNA polymerase II, likely functions as a transcriptional regulator essential for early embryogenesis in Arabidopsis.
Fatty acids in serum cholesteryl esters in relation to asthma and lung function in children
Authors: Bolte G. , Kompauer I. , Fobker M. , Cullen P. , Keil U. , von Mutius E. , Weiland S. K. 
Published: February 2006

SummaryBackground
Dietary fatty acid intake has been proposed to contribute to asthma development with n‐6 polyunsaturated fatty acids (PUFA) having a detrimental and n‐3 PUFA a protective effect.Objective
The aim of our analysis was to explore the relationship between fatty acid composition of serum cholesteryl esters as marker of dietary intake and prevalence of asthma, impaired lung function and bronchial hyper‐responsiveness in children.Methods
The study population consisted of 242 girls and 284 boys aged 8–11 years, living in Munich, Germany. Data were collected by parental questionnaire, lung function measurement and skin prick test according to the International Study of Asthma and Allergies in Childhood phase II protocol. Confounder‐adjusted odds ratios (OR) with 95% confidence intervals (CI) were calculated for the association between quartiles of fatty acid concentration and health outcomes with the first quartile as reference.Results
n‐3 PUFA: levels of eicosapentaenoic acid were not related to asthma and impaired lung function. Linolenic acid levels were positively associated with current asthma (OR for fourth quartile 3.35, 95% CI 1.29–8.66). Forced expiratory volume in 1 s (FEV1) values decreased with increasing levels of linolenic acid (p for trend=0.057). n‐6 PUFA: there was a strong positive association between arachidonic acid levels and current asthma (OR4th quartile 4.54, 1.77–11.62) and a negative association with FEV1 (P=0.036). In contrast, linoleic acid was negatively related to current asthma (OR4th quartile 0.34, 0.14–0.87) and FEV1 values increased with increasing levels of linoleic acid (P=0.022). The ratio of measured n‐6 to n‐3 PUFA as well as levels of palmitic and oleic acid were not consistently related to asthma or lung function.Conclusion
Our data do not support the hypothesis of a protective role of n‐3 PUFA. Elevated arachidonic acid levels in children with asthma may be because of a disturbed balance in the metabolism of n‐6 PUFA or may be secondary to inflammation in these patients.
Influence of short‐term exposure to airborne Der p 1 and volatile organic compounds on skin barrier function and dermal blood flow in patients with atopic eczema and healthy individuals
Authors: Huss‐Marp J. , Eberlein‐König B. , Breuer K. , Mair S. , Ansel A. , Darsow U. , Krämer U. , Mayer E. , Ring J. , Behrendt H. 
Published: February 2006

SummaryBackground
Epidemiological studies indicate environmental pollutants to be involved in the increase in the prevalence of allergic diseases. In human exposure studies, volatile organic compounds (VOCs) have been shown to cause exacerbations of allergic asthma whereas, no data concerning atopic eczema (AE) are available.Objective
We investigated the effect of airborne VOCs on the skin of patients with AE and controls in the presence or absence of house dust mite allergen, Der p 1.Methods
In a double‐blind crossover study, 12 adults with AE and 12 matched healthy volunteers were exposed on their forearms to Der p 1 and subsequently to a mixture of 22 VOCs (M22, 5 mg/m3) in a total body exposure chamber for 4 h. Transepidermal water loss (TEWL) and skin blood flow were measured in all subjects before, during and after exposure. Additionally, an atopy patch test (APT) with Der p 1 was applied to the skin after exposure.Results
A significant increase in transepidermal water loss was observed 48 h after exposure to VOCs as compared with exposure with filtered air in all individuals (mean difference: +34%; 95% Confidence Interval: 7–69%). Prior Der p 1 exposure resulted in a significant rise of dermal blood flow after 48 h in patients with AE but not in controls. Six out of seven patients showed enhanced atopy patch test (APT) reactions to HDM allergen after previous exposure to VOCs.Conclusion
Our results show that exposure to VOCs – at concentrations commonly found in indoor environments – can damage the epidermal barrier and enhance the adverse effect of Der p 1 on sensitized subjects with AE. These findings may contribute to a better understanding of the mechanisms underlying the increase in prevalence and exacerbation of AE.
The effect of genotype and culture medium on somatic embryogenesis and plant regeneration from mature embryos of fourteen apomictic cultivars of buffel grass (Cenchrus ciliaris L.)
Authors: Colomba E. L. , Grunberg K. , Griffa S. , Ribotta A. , Mroginski L. , Biderbost E. 
Published: February 2006

AbstractBuffel grass (Cenchrus ciliaris L.) is an important apomictic grass used as forage for ruminant livestock. Biotechnological methods provide opportunities for producing new germplasm. Mature embryos of fourteen buffel grass apomictic cultivars (2n = 4x = 36) were used to induce embryogenic callus formation using a basal medium supplemented with 3% sucrose and with the testing of five concentrations of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and four concentrations of 6‐benzylaminopurine (BAP). The effects of cultivar and culture medium on callus induction and plant regeneration were evaluated. Significant differences were observed among the fourteen cultivars and the five concentrations of 2,4‐D (P < 0·01). Values for embryogenic callus production varied from 0 to 86·7. Most cultivars showed the highest level of embryogenic callus production on the medium with the concentration of 3 mg L−1 2,4‐D. The addition of different BAP concentrations in combination with 2,4‐D in the medium inhibited embryogenic callus growth and did not permit plant regeneration. The data clearly demonstrated that the genotype and concentrations of 2,4‐D had significant effects both on the frequency of embryonic callus formation from mature embryos and on the subsequent efficiency of plant regeneration of apomictic cultivars of buffel grass. Cultivars Biloela and Nunbank showed the greatest efficiency in in vitro culture response.
The infection of Festuca rubra subsp. pruinosa by Epichloë festucae
Authors: Zabalgogeazcoa I. , Romo M. , Keck E. , Vázquez de Aldana B. R. , García Ciudad A. , García Criado B. 
Published: February 2006

Abstract Festuca rubra subsp. pruinosa is a grass that inhabits the sea cliffs of the Atlantic coasts of Europe. Four populations of this plant in the northern coast of Galicia, in northern Spain, were analysed for the presence of fungal endophytes. Of the plants included in the study, on average 0·69 were infected by an intercellular fungal endophyte. Using morphological and molecular characters, this endophyte was identified as Epichloë festucae, a clavicipitaceous, seed‐transmitted species. A half‐sibling line, consisting of endophyte‐free and endophyte‐infected plants, was developed and used to test whether the presence of the fungus affected the response of the plants to salinity. Dry weights of infected or uninfected plants, watered with sea‐water solutions or tap water, did not significantly differ.
Influence of human menopausal gonadotrophin treatment on testicular blood flow and on seminal plasma nitric oxide levels in infertile males1
Authors: Matteo M. , Cicinelli E. , Baldini D. , Cho Y. S. , Ignarro L. J. , Vitarelli A. , Boffoli D. , Greco P. 
Published: February 2006

SummaryGonadotrophin treatment is capable of increasing intratesticular blood flow and improving sperm fertilization potential. A nitric oxide (NO)‐mediated mechanism may play a role. This study aimed at evaluating whether the increase in intratesticular blood flow, in response to human menopausal gonadotrophin (hMG) treatment, is accompanied by an increase in seminal plasma NO levels in 20 normogonadotropic males affected by severe oligoasthenoteratozoospermia. Patients received 150 IU of hMG, three times a week for 3 months. Before starting treatment and at month 3 of therapy, levels of NO in the seminal plasma were determined, followed by ultrasound scanning of testis, Doppler evaluation of intratesticular vascular resistance, serum hormone and conventional semen evaluation. Statistical analysis was performed by using Wilcoxon test; the limit of statistical significance was p < 0.05. At the end of treatment, seminal plasma concentration of NO, conventional semen parameters and testicular volume did not increase significantly. Follicle‐stimulating hormone serum level significantly increased (p = 0.014) after treatment, whereas luteinizing hormone, testosterone and oestradiol values did not change. The resistance index of both intratesticular arteries significantly decreased (p = 0.012 and 0.005 for right and left testes respectively). The results of this study confirmed the positive effect of exogenous hMG on testicular blood flow, but failed to demonstrate any effect of hMG treatment on NO levels in the seminal plasma in infertile males.