bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tryptophan-Derived Metabolites Are Required for Antifungal Defense in the Arabidopsismlo2Mutant
Authors: Consonni Chiara , Bednarek Paweł , Humphry Matt , Francocci Fedra , Ferrari Simone , Harzen Anne , Ver Loren van Themaat Emiel , Panstruga Ralph 
Published: December 2009

AbstractArabidopsis (Arabidopsis thaliana) genes MILDEW RESISTANCE LOCUS O2 (MLO2), MLO6, and MLO12 exhibit unequal genetic redundancy with respect to the modulation of defense responses against powdery mildew fungi and the control of developmental phenotypes such as premature leaf decay. We show that early chlorosis and necrosis of rosette leaves in mlo2 mlo6 mlo12 mutants reflects an authentic but untimely leaf senescence program. Comparative transcriptional profiling revealed that transcripts of several genes encoding tryptophan biosynthetic and metabolic enzymes hyperaccumulate during vegetative development in the mlo2 mlo6 mlo12 mutant. Elevated expression levels of these genes correlate with altered steady-state levels of several indolic metabolites, including the phytoalexin camalexin and indolic glucosinolates, during development in the mlo2 single mutant and the mlo2 mlo6 mlo12 triple mutant. Results of genetic epistasis analysis suggest a decisive role for indolic metabolites in mlo2-conditioned antifungal defense against both biotrophic powdery mildews and a camalexin-sensitive strain of the necrotrophic fungus Botrytis cinerea. The wound- and pathogen-responsive callose synthase POWDERY MILDEW RESISTANCE4/GLUCAN SYNTHASE-LIKE5 was found to be responsible for the spontaneous callose deposits in mlo2 mutant plants but dispensable for mlo2-conditioned penetration resistance. Our data strengthen the notion that powdery mildew resistance of mlo2 genotypes is based on the same defense execution machinery as innate antifungal immune responses that restrict the invasion of nonadapted fungal pathogens.
AtMetExpress Development: A Phytochemical Atlas of Arabidopsis Development
Authors: Matsuda Fumio , Hirai Masami Y. , Sasaki Eriko , Akiyama Kenji , Yonekura-Sakakibara Keiko , Provart Nicholas J. , Sakurai Tetsuya , Shimada Yukihisa , Saito Kazuki 
Published: December 2009

AbstractPlants possess many metabolic genes for the production of a wide variety of phytochemicals in a tissue-specific manner. However, the metabolic systems behind the diversity and tissue-dependent regulation still remain unknown due to incomplete characterization of phytochemicals produced in a single plant species. Thus, having a metabolome dataset in addition to the genome and transcriptome information resources would enrich our knowledge of plant secondary metabolism. Here we analyzed phytochemical accumulation during development of the model plant Arabidopsis (Arabidopsis thaliana) using liquid chromatography-mass spectrometry in samples covering many growth stages and organs. We also obtained tandem mass spectrometry spectral tags of many metabolites as a resource for elucidation of metabolite structure. These are part of the AtMetExpress metabolite accumulation atlas. Based on the dataset, we detected 1,589 metabolite signals from which the structures of 167 metabolites were elucidated. The integrated analyses with transcriptome data demonstrated that Arabidopsis produces various phytochemicals in a highly tissue-specific manner, which often accompanies the expression of key biosynthesis-related genes. We also found that a set of biosynthesis-related genes is coordinately expressed among the tissues. These data suggested that the simple mode of regulation, transcript to metabolite, is an origin of the dynamics and diversity of plant secondary metabolism.
Glucanases and Chitinases as Causal Agents in the Protection ofAcaciaExtrafloral Nectar from Infestation by Phytopathogens
Authors: GonzÁlez-Teuber Marcia , Pozo María J. , Muck Alexander , Svatos Ales , Adame-Álvarez Rosa M. , Heil Martin 
Published: December 2009

AbstractNectars are rich in primary metabolites and attract mutualistic animals, which serve as pollinators or as an indirect defense against herbivores. Their chemical composition makes nectars prone to microbial infestation. As protective strategy, floral nectar of ornamental tobacco (Nicotiana langsdorffii × Nicotiana sanderae) contains “nectarins,” proteins producing reactive oxygen species such as hydrogen peroxide. By contrast, pathogenesis-related (PR) proteins were detected in Acacia extrafloral nectar (EFN), which is secreted in the context of defensive ant-plant mutualisms. We investigated whether these PR proteins protect EFN from phytopathogens. Five sympatric species (Acacia cornigera, A. hindsii, A. collinsii, A. farnesiana, and Prosopis juliflora) were compared that differ in their ant-plant mutualism. EFN of myrmecophytes, which are obligate ant-plants that secrete EFN constitutively to nourish specialized ant inhabitants, significantly inhibited the growth of four out of six tested phytopathogenic microorganisms. By contrast, EFN of nonmyrmecophytes, which is secreted only transiently in response to herbivory, did not exhibit a detectable inhibitory activity. Combining two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis with nanoflow liquid chromatography-tandem mass spectrometry analysis confirmed that PR proteins represented over 90% of all proteins in myrmecophyte EFN. The inhibition of microbial growth was exerted by the protein fraction, but not the small metabolites of this EFN, and disappeared when nectar was heated. In-gel assays demonstrated the activity of acidic and basic chitinases in all EFNs, whereas glucanases were detected only in EFN of myrmecophytes. Our results demonstrate that PR proteins causally underlie the protection of Acacia EFN from microorganisms and that acidic and basic glucanases likely represent the most important prerequisite in this defensive function.
Generation of Backbone-Free, Low Transgene Copy Plants by Launching T-DNA from theAgrobacteriumChromosome
Authors: Oltmanns Heiko , Frame Bronwyn , Lee Lan-Ying , Johnson Susan , Li Bo , Wang Kan , Gelvin Stanton B. 
Published: December 2009

AbstractIn both applied and basic research, Agrobacterium-mediated transformation is commonly used to introduce genes into plants. We investigated the effect of three Agrobacterium tumefaciens strains and five transferred (T)-DNA origins of replication on transformation frequency, transgene copy number, and the frequency of integration of non-T-DNA portions of the T-DNA-containing vector (backbone) into the genome of Arabidopsis (Arabidopsis thaliana) and maize (Zea mays). Launching T-DNA from the picA locus of the Agrobacterium chromosome increases the frequency of single transgene integration events and almost eliminates the presence of vector backbone sequences in transgenic plants. Along with novel Agrobacterium strains we have developed, our findings are useful for improving the quality of T-DNA integration events.
The Missing Link in Plant Histidine Biosynthesis: Arabidopsismyoinositol monophosphatase-like2Encodes a Functional Histidinol-Phosphate Phosphatase
Authors: Petersen Lindsay N. , Marineo Sandra , Mandalà Salvatore , Davids Faezah , Sewell Bryan T. , Ingle Robert A. 
Published: December 2009

AbstractHistidine (His) plays a critical role in plant growth and development, both as one of the standard amino acids in proteins, and as a metal-binding ligand. While genes encoding seven of the eight enzymes in the pathway of His biosynthesis have been characterized from a number of plant species, the identity of the enzyme catalyzing the dephosphorylation of histidinol-phosphate to histidinol has remained elusive. Recently, members of a novel family of histidinol-phosphate phosphatase proteins, displaying significant sequence similarity to known myoinositol monophosphatases (IMPs) have been identified from several Actinobacteria. Here we demonstrate that a member of the IMP family from Arabidopsis (Arabidopsis thaliana), myoinositol monophosphatase-like2 (IMPL2; encoded by At4g39120), has histidinol-phosphate phosphatase activity. Heterologous expression of IMPL2, but not the related IMPL1 protein, was sufficient to rescue the His auxotrophy of a Streptomyces coelicolor hisN mutant. Homozygous null impl2 Arabidopsis mutants displayed embryonic lethality, which could be rescued by supplying plants heterozygous for null impl2 alleles with His. In common with the previously characterized HISN genes from Arabidopsis, IMPL2 was expressed in all plant tissues and throughout development, and an IMPL2:green fluorescent protein fusion protein was targeted to the plastid, where His biosynthesis occurs in plants. Our data demonstrate that IMPL2 is the HISN7 gene product, and suggest a lack of genetic redundancy at this metabolic step in Arabidopsis, which is characteristic of the His biosynthetic pathway.
ArabidopsisFormin3 Directs the Formation of Actin Cables and Polarized Growth in Pollen Tubes
Authors: Ye Jianrong , Zheng Yiyan , Yan An , Chen Naizhi , Wang Zhangkui , Huang Shanjin , Yang Zhenbiao 
Published: December 2009

AbstractCytoplasmic actin cables are the most prominent actin structures in plant cells, but the molecular mechanism underlying their formation is unknown. The function of these actin cables, which are proposed to modulate cytoplasmic streaming and intracellular movement of many organelles in plants, has not been studied by genetic means. Here, we show that Arabidopsis thaliana formin3 (AFH3) is an actin nucleation factor responsible for the formation of longitudinal actin cables in pollen tubes. The Arabidopsis AFH3 gene encodes a 785–amino acid polypeptide, which contains a formin homology 1 (FH1) and a FH2 domain. In vitro analysis revealed that the AFH3 FH1FH2 domains interact with the barbed end of actin filaments and have actin nucleation activity in the presence of G-actin or G actin-profilin. Overexpression of AFH3 in tobacco (Nicotiana tabacum) pollen tubes induced excessive actin cables, which extended into the tubes' apices. Specific downregulation of AFH3 eliminated actin cables in Arabidopsis pollen tubes and reduced the level of actin polymers in pollen grains. This led to the disruption of the reverse fountain streaming pattern in pollen tubes, confirming a role for actin cables in the regulation of cytoplasmic streaming. Furthermore, these tubes became wide and short and swelled at their tips, suggesting that actin cables may regulate growth polarity in pollen tubes. Thus, AFH3 regulates the formation of actin cables, which are important for cytoplasmic streaming and polarized growth in pollen tubes.
Ethylene Interacts with Abscisic Acid to Regulate Endosperm Rupture during Germination: A Comparative Approach UsingLepidium sativumandArabidopsis thaliana
Authors: Linkies Ada , Müller Kerstin , Morris Karl , Turečková Veronika , Wenk Meike , Cadman Cassandra S.C. , Corbineau Françoise , Strnad Miroslav , Lynn James R. , Finch-Savage William E. , Leubner-Metzger Gerhard 
Published: December 2009

AbstractThe micropylar endosperm cap covering the radicle in the mature seeds of most angiosperms acts as a constraint that regulates seed germination. Here, we report on a comparative seed biology study with the close Brassicaceae relatives Lepidium sativum and Arabidopsis thaliana showing that ethylene biosynthesis and signaling regulate seed germination by a mechanism that requires the coordinated action of the radicle and the endosperm cap. The larger seed size of Lepidium allows direct tissue-specific biomechanical, biochemical, and transcriptome analyses. We show that ethylene promotes endosperm cap weakening of Lepidium and endosperm rupture of both species and that it counteracts the inhibitory action of abscisic acid (ABA) on these two processes. Cross-species microarrays of the Lepidium micropylar endosperm cap and the radicle show that the ethylene-ABA antagonism involves both tissues and has the micropylar endosperm cap as a major target. Ethylene counteracts the ABA-induced inhibition without affecting seed ABA levels. The Arabidopsis loss-of-function mutants ACC oxidase2 (aco2; ethylene biosynthesis) and constitutive triple response1 (ethylene signaling) are impaired in the 1-aminocyclopropane-1-carboxylic acid (ACC)-mediated reversion of the ABA-induced inhibition of seed germination. Ethylene production by the ACC oxidase orthologs Lepidium ACO2 and Arabidopsis ACO2 appears to be a key regulatory step. Endosperm cap weakening and rupture are promoted by ethylene and inhibited by ABA to regulate germination in a process conserved across the Brassicaceae.
Mutations of an α1,6 Mannosyltransferase Inhibit Endoplasmic Reticulum–Associated Degradation of Defective Brassinosteroid Receptors inArabidopsis
Authors: Hong Zhi , Jin Hua , Fitchette Anne-Catherine , Xia Yang , Monk Andrew M. , Faye Loïc , Li Jianming 
Published: December 2009

AbstractAsn-linked glycans, or the glycan code, carry crucial information for protein folding, transport, sorting, and degradation. The biochemical pathway for generating such a code is highly conserved in eukaryotic organisms and consists of ordered assembly of a lipid-linked tetradeccasaccharide. Most of our current knowledge on glycan biosynthesis was obtained from studies of yeast asparagine-linked glycosylation (alg) mutants. By contrast, little is known about biosynthesis and biological functions of N-glycans in plants. Here, we show that loss-of-function mutations in the Arabidopsis thaliana homolog of the yeast ALG12 result in transfer of incompletely assembled glycans to polypeptides. This metabolic defect significantly compromises the endoplasmic reticulum–associated degradation of bri1-9 and bri1-5, two defective transmembrane receptors for brassinosteroids. Consequently, overaccumulated bri1-9 or bri1-5 proteins saturate the quality control systems that retain the two mutated receptors in the endoplasmic reticulum and can thus leak out of the folding compartment, resulting in phenotypic suppression of the two bri1 mutants. Our results strongly suggest that the complete assembly of the lipid-linked glycans is essential for successful quality control of defective glycoproteins in Arabidopsis.
Class I α-Mannosidases Are Required for N-Glycan Processing and Root Development inArabidopsis thaliana
Authors: Liebminger Eva , Hüttner Silvia , Vavra Ulrike , Fischl Richard , Schoberer Jennifer , Grass Josephine , Blaukopf Claudia , Seifert Georg J. , Altmann Friedrich , Mach Lukas , Strasser Richard 
Published: December 2009

AbstractIn eukaryotes, class I α-mannosidases are involved in early N-glycan processing reactions and in N-glycan–dependent quality control in the endoplasmic reticulum (ER). To investigate the role of these enzymes in plants, we identified the ER-type α-mannosidase I (MNS3) and the two Golgi-α-mannosidase I proteins (MNS1 and MNS2) from Arabidopsis thaliana. All three MNS proteins were found to localize in punctate mobile structures reminiscent of Golgi bodies. Recombinant forms of the MNS proteins were able to process oligomannosidic N-glycans. While MNS3 efficiently cleaved off one selected α1,2-mannose residue from Man9GlcNAc2, MNS1/2 readily removed three α1,2-mannose residues from Man8GlcNAc2. Mutation in the MNS genes resulted in the formation of aberrant N-glycans in the mns3 single mutant and Man8GlcNAc2 accumulation in the mns1 mns2 double mutant. N-glycan analysis in the mns triple mutant revealed the almost exclusive presence of Man9GlcNAc2, demonstrating that these three MNS proteins play a key role in N-glycan processing. The mns triple mutants displayed short, radially swollen roots and altered cell walls. Pharmacological inhibition of class I α-mannosidases in wild-type seedlings resulted in a similar root phenotype. These findings show that class I α-mannosidases are essential for early N-glycan processing and play a role in root development and cell wall biosynthesis in Arabidopsis.
Regulation ofArabidopsisBrassinosteroid Signaling by Atypical Basic Helix-Loop-Helix Proteins
Authors: Wang Hao , Zhu Yongyou , Fujioka Shozo , Asami Tadao , Li Jiayang , Li Jianming 
Published: December 2009

AbstractBasic helix-loop-helix (bHLH) proteins are highly conserved transcription factors critical for cell proliferation and differentiation. Recent studies have implicated bHLH proteins in many plant signaling processes, including brassinosteroid (BR) signaling. Here, we report identification of two families of atypical bHLH proteins capable of modulating BR signaling. We found that activation-tagged bri1 suppressor 1-Dominant (atbs1-D), previously identified as a dominant suppressor of a weak BR receptor mutant bri1-301, was caused by overexpression of a 93–amino acid atypical bHLH protein lacking amino acids critical for DNA binding. Interestingly, atbs1-D only suppresses weak BR mutants, while overexpression of a truncated ATBS1 lacking the basic motif also rescues bri1-301, suggesting that ATBS1 likely stimulates BR signaling by sequestering negative BR signaling components. A yeast two-hybrid screen using ATBS1 as bait discovered four ATBS1-Interacting Factors (AIFs) that are members of another atypical bHLH protein subfamily. AIF1 exhibits an overlapping expression pattern with ATBS1 and its homologs and interacts with ATBS1 in vitro and in vivo. AIF1 overexpression nullifies the suppressive effect of atbs1-D on bri1-301 and results in dwarf transgenic plants resembling BR mutants. By contrast, silencing of AIF1 partially suppressed the bri1-301 phenotype. Our results suggested that plants use these atypical bHLH proteins to regulate BR signaling.
Audit fee premium and auditor change: the effect of Sarbanes‐Oxley Act
Authors: Ebrahim Ahmed 
Published: December 2009

PurposeThe purpose of this paper is to provide more comprehensive analysis of the effects of Sarbanes‐Oxley (SOX) Act on both audit fee premium and auditor change in the US audit market.Design/methodology/approachThe audit fee premium model is employed to track the trend in audit fee premium between 2000 and 2006 for small accelerated filers compared with large accelerated filers and non‐accelerated filers and how the change in auditor affected such trend around the enactment of SOX.FindingsThe results indicate a significant shift in audit fee premium during early years of SOX compliance especially for small accelerated filers compared with large accelerated filers or non‐accelerated filers. Such shift started to wind down during 2006 after the initial application of SOX requirements. Although clients who switched from big to non‐big auditors have experienced a slower increase in their audit fees, these fee savings are lower for small accelerated filers during 2004 and 2005 with the increasing demand for audit services in the US audit industry during these years.Practical implicationsThe compliance costs of significant regulatory changes like SOX may be upfront loaded but their benefits are long‐term benefits in terms of higher quality of financial reporting and better internal controls over financial reporting. When analyzing the effects of such regulatory changes, practitioners and researchers should factor these costs and benefits over a sufficient time horizon.Originality/valueMore comprehensive analysis of SOX effects on the US audit industry not only in the short run during early compliance years, but also in the longer run after the initial setup process.
Audit pricing and the Big4 fee premium: evidence from Belgium
Authors: Van Caneghem Tom 
Published: December 2009

PurposeThe purpose of this paper is to study audit pricing and the Big4 fee premium in Belgium. While a number of studies have already explored these issues, the Belgian audit market provides an interesting setting to gain an additional insight into the pricing of audit services for many reasons (e.g. audit market concentration in Belgium is much lower than in other countries, the Belgian audit market mainly consists of non‐listed firms, etc.).Design/methodology/approachBesides the traditional audit fee model, based on seminal work by Simunic, the paper also estimates regression models in which the author allows coefficients to vary across Big4 and non‐Big4 auditors and control for self‐selection (based on a two‐stage procedure).FindingsUsing the traditional audit fee model, results suggest that Big4 auditors receive (or are able to charge) a fee premium compared to non‐Big4 auditors. Nevertheless, when the author allows regression coefficients to vary across Big4 and non‐Big4 auditors and control for self‐selection, the aforementioned finding does no longer hold. The results reveal differences in fee structures between Big4 and non‐Big4 auditors and suggest that Big4 auditors consider a richer set of variables when setting their fees.Research limitations/implicationsSince Belgian firms are only required to disclose audit fees as from 2007 onwards, the analyses are based on data for one year only.Practical implicationsAn important implication, at least from an academic point of view, is that the results clearly illustrate and corroborate the need to control for self‐selection when modelling audit fees (while this issue has been ignored by recent audit fee studies). The findings also have implications for the (Belgian) auditing profession. For example, the fact that significant differences are observed in audit pricing between the Big4 and non‐Big4 firms may have an impact on the (Belgian) audit services market (e.g. it might influence the competitive nature of the tendering process).Originality/valueUsing a two‐stage procedure, the results corroborate the need to control for self‐selection in modeling audit fees (an issue that has been largely ignored in the audit fee literature). In addition, the results reveal that Big4 and non‐Big4 auditors have different fee structures and that it is therefore important to allow the regression coefficients (and not only the intercept) to vary across both groups. Finally, the findings add to the very scarce evidence on audit pricing for non‐listed firms.