bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcriptional and post‐transcriptional processes regulate gene expression in oxygen‐deprived roots of maize
Authors: Fennoy Sheila L. , Nong Thoa , Bailey‐Serres Julia 
Published: March 2003

SummaryTo investigate the regulation of gene expression in maize (Zea maysL.) in response to oxygen deprivation (flooding), we quantitated run‐on transcription in isolated nuclei, steady‐state mRNA accumulation and mRNA loading with ribosomes for seven genes that encode proteins synthesized predominantly in oxygen‐deprived roots (anaerobic polypeptides) and seven genes that encode proteins synthesized in aerobic roots (aerobic polypeptides). Run‐on transcription of anaerobic polypeptide genes was induced in response to oxygen deprivation and run‐on transcription of the aerobic polypeptide genes continued during the stress treatment. The increased accumulation of mRNAs that encode anaerobic polypeptides occurred concomitant with the induction of gene transcription and efficient association of these mRNAs with large polysomes. The steady‐state accumulation of aerobic polypeptide mRNAs was within twofold of aerobic levels and in a number of cases fewer ribosomes were loaded per transcript. These results demonstrate that selected synthesis of anaerobic polypeptides involves transcriptional as well as significant post‐transcriptional regulation of gene expression. The repression of synthesis of many aerobic polypeptides occurs without interruption of gene transcription and is due to translational regulation and possibly the sequestration of mRNAs on mRNPs. Ribosome loading patterns indicated that this translational control occurs at both initiation and post‐initiation phases in a message‐specific manner.
Thetitanmutants ofArabidopsisare disrupted in mitosis and cell cycle control during seed development
Authors: Liu Chun‐ming , Meinke David W. 
Published: March 2003

Summary We describe in this report a novel class of mutants that should facilitate the identification of genes required for progression through the mitotic cell cycle during seed development in angiosperms. Three non‐allelic

titan

(

ttn

) mutants with related but distinct phenotypes are characterized. The common feature among these mutants is that endosperm nuclei become greatly enlarged and highly polyploid. The mutant embryo is composed of a few giant cells in

ttn1

, several small cells in

ttn2

, and produces a normal plant in

ttn3

. Condensed chromosomes arrested at prophase of mitosis are found in the free nuclear endosperm of

ttn1

and

ttn2

seeds. Large mitotic figures with excessive numbers of chromosomes are visible in

ttn3

endosperm. The

ttn1

mutation appears to disrupt cytoskeletal organization because endosperm nuclei fail to migrate to the chalazal end of the seed. How double fertilization leads to the establishment of distinct patterns of mitosis and cytokinesis in the embryo and endosperm is a central question in plant reproductive biology. Molecular isolation of

TITAN

genes should help to answer this question, as well as related issues concerning cell cycle regulation, chromosome movement and endosperm identity in angiosperms.
A rapid method to screen for cell‐wall mutants using discriminant analysis of Fourier transform infrared spectra
Authors: Chen Limei , Carpita Nicholas C. , Reiter Wolf‐Dieter , Wilson Reginald H. , Jeffries Charles , McCann Maureen C. 
Published: March 2003

Summary We have developed a rapid method to screen large numbers of mutant plants for a broad range of cell wall phenotypes using Fourier transform infrared (FTIR) microspectroscopy of leaves. We established and validated a model that can discriminate between the leaves of wild‐type and a previously defined set of cell‐wall mutants of

Arabidopsis

. Exploratory principal component analysis indicated that mutants deficient in different cell‐wall sugars can be distinguished from each other. Discrimination of cell‐wall mutants from wild‐type was independent of variability in starch content or additional unrelated mutations that might be present in a heavily mutagenised population. We then developed an analysis of FTIR spectra of leaves obtained from over 1000 mutagenised flax plants, and selected 59 plants whose spectral variation from wild‐type was significantly out of the range of a wild‐type population, determined by Mahalanobis distance. Cell wall sugars from the leaves of selected putative mutants were assayed by gas chromatography‐mass spectrometry and 42 showed significant differences in neutral sugar composition. The FTIR spectra indicated that six of the remaining 17 plants have altered ester or protein content. We conclude that linear discriminant analysis of FTIR spectra is a robust method to identify a broad range of structural and architectural alterations in cell walls, appearing as a consequence of developmental regulation, environmental adaptation or genetic modification.
Altered plastidic ATP/ADP‐transporter activity influences potato (Solanum tuberosumL.) tuber morphology, yield and composition of tuber starch
Authors: Tjaden Joachim , Möhlmann Torsten , Kampfenkel Karlheinz , Neuhaus Gudrun Henrichs andH. Ekkehard 
Published: March 2003

Summary The metabolic function of the plastidic ATP/ADP transporter (AATP) in heterotrophic plastids was examined in transgenic potato plants that exhibited increased or decreased amounts of the protein. Altered mRNA levels correlated with activities of the plastidic ATP/ADP transporter. Potato tubers with decreased plastidic ATP/ADP transporter activities exhibited reduced starch contents whereas sense lines accumulated increased amounts of tuber starch. Starch from wild‐type tubers had an amylose content of 18.8%, starch from antisense plants contained 11.5–18.0% amylose, whereas starch from sense plants had levels of 22.7–27.0%. The differences in physiological parameters were accompanied with altered tuber morphology. These changes are discussed with respect to the stromal ATP supply during starch biosynthesis.
Fatty acids and lysophospholipids as potential second messengers in auxin action. Rapid activation of phospholipase A2 activity by auxin in suspension‐cultured parsley and soybean cells
Authors: Holk Roland U. Paul andré , Scherer Günther F. E. 
Published: March 2003

Summary Activation of cytosolic phospholipase A2 is a typical signal transduction reaction in animal cells and occurs in plants in response to auxin, elicitors and wounding. Exogenously added fluorescent bis‐BODIPY‐phosphatidylcholine was taken up and hydrolysed by a cellular phospholipase A2. Rapid activation of a phospholipase A2 by auxin in suspension‐cultured parsley (

Petrosilenum crispum

L.) and soybean (

Glycine max

L.) cells was shown by detection and quantification of fluorescent reaction products of phospholipase A2. Hormone‐triggered fluorescent fatty acid accumulation could be detected as early as 5 min. Auxins at 2 μM or higher concentrations activated phospholipase A2 and fluorescent fatty acids accumulated 1.1‐ to threefold after 90–120 min, depending on the auxin concentration. Fluorescent lysolipid did not accumulate up to 150 μM auxin. Known inhibitors of phospholipase A2 inhibited hormone‐dependent fluorescent fatty acid accumulation in cell cultures and, previously, elongation growth in etiolated zucchini hypocotyl segments (

Scherer & Arnold (1997

)

Planta

202, 462–469). When lipids were labeled by [14C]‐choline and [14C]‐ethanolamine the corresponding lysophospholipids could be quantified in cell extracts. Radioactive lysophospholipids accumulated as rapidly as 1–2 min after auxin treatment but only at concentrations well above 100 μM auxin. We hypothesize that phospholipase A2 activation is an early intermediate step between receptor and downstream responses. We hypothesize that fatty acid(s) could be second messengers in several auxin functions, especially in cell elongation. Lysophospholipids seem to be indicators or second messengers for stress caused by high auxin concentrations or may have different auxin‐linked functions and are also known to accumulate during elicitor action.
A rice homolog of Cdk7/MO15 phosphorylates both cyclin‐dependent protein kinases and the carboxy‐terminal domain of RNA polymerase II
Authors: Yamaguchi Masatoshi , Umeda Masaaki , Uchimiya Hirofumi 
Published: March 2003

Summary The activation of cyclin‐dependent protein kinases (CDKs) requires phosphorylation of a threonine residue within the T‐loop by a CDK‐activating kinase (CAK). The R2 protein of rice is very similar to CAKs of animals and fission yeast at the amino acid level but phosphorylation by R2 has not yet been demonstrated. When

R2

was overexpressed in a CAK‐deficient mutant of budding yeast, it suppressed the temperature sensitivity of the mutation. Immunoprecipitates of rice proteins with the anti‐R2 antibody phosphorylated human CDK2, one of the rice CDKs (Cdc2Os1), and the carboxy‐terminal domain (CTD) of the largest subunit of RNA polymerase II of

Arabidopsis

. Mutational analysis indicated that R2 phosphorylated the threonine residue within the T‐loop of CDK2 and Cdc2Os1. R2 was found mainly in two protein complexes which had molecular masses of 190 kDa and 70 kDa, respectively, whilst the CDK‐ and CTD‐kinase activities associated with R2 were identified in a complex of 105 kDa. These results indicate that R2 is closely related to CAKs of animals and fission yeast in terms of its phosphorylation activity and, moreover, that this CAK of rice is distinct from a CAK of the dicotyledonous plant

Arabidopsis

.
Plant responses to genotoxic stress are linked to an ABA/salinity signaling pathway
Authors: Albinsky Doris , Masson Jean E. , Bogucki Augustyn , Afsar Karin , Vass Imre , Nagy Ferenc , Paszkowski Jerzy 
Published: March 2003

Summary Cells have developed a complex network of reactions to avoid or reduce the deleterious consequences of DNA damage. Responses to genotoxic stress include activation of distinct stress signaling pathways, delay of cell cycle progression and induction of DNA repair. In contrast to other organisms, it is not known which signal transduction pathways sense genotoxic stress in plants. Here we describe an

Arabidopsis

mutant (

uvs66

) that appears to be affected in the perception of signals triggered by genotoxic treatments. The mutant

uvs66

was identified as hypersensitive to UV‐C and to the DNA‐damaging chemicals methyl methane sulfonate (MMS) and mitomycin C (MMC), but seems to perform light dependent repair, nucleotide excision repair and homologous recombinational repair as efficiently as the wild type. Exposure of

uvs66

plants to various environmental stresses revealed a normal response, with the exception of elevated salinity and abscisic acid (ABA). The hypersensitivity to NaCl and ABA is correlated with aberrant regulation of transcripts that are regulated by ABA (

RAB18

), or are induced by DNA damaging treatments (

AtRAD51

). The properties of the mutant

uvs66

suggest an unexpected link between ABA and/or salt stress mediated signals and genotoxic stress responses, and provide an important connection between the physiological and genetic responses of plants to abiotic stress factors.
Identification of genes expressed during earlyArabidopsiscarpel development by mRNA differential display: characterisation ofATCEL2, a novel endo‐1,4‐β‐D‐glucanase gene
Authors: Yung Mei‐Hing , Schaffer Robert , Putterill Jo 
Published: March 2003

Summary The floral homeotic gene

AGAMOUS
(AG) imparts carpel identity on the fourth whorl of floral organs in wild‐typeArabidopsisflowers. Less is known about the genes that regulate carpel patterning and differentiation. To identify candidate regulators, we screened for genes expressed in developing carpels. SinceArabidopsiscarpels are difficult to isolate, we used whole inflorescence apices of two floral homeotic mutants (pi and pi ag) and mRNA differential display, to identify carpel transcripts. Two of the resulting cDNA clones were shown to be expressed predominantly in flowers. They encodedAGL11,a MADS box transcription factor known to be expressed in the carpel and ovules, and a novelArabidopsisendo‐1,4‐β‐D‐glucanase (ATCEL2).In situhybridisation localised theATCEL2transcript to the developing septum and ovule primordia of young carpels.
Silencing of an aleurone‐specific gene in transgenic rice is caused by a rearranged transgene
Authors: Morino Kazuko , Olsen Odd‐Arne , Shimamoto Ko 
Published: March 2003

Summary In rice, silencing of the aleurone‐specific

Ltp2‐gus

transgene, causing easily detectable staining patterns on the grain surface, offers a convenient tool to study quantitative aspects of gene silencing in monocots. In this paper we analyzed phenotypes, occurrence, inheritance and environmental effects on the silencing. We also report on the cloning of transgenes, determination of their structure and analysis of transcripts from the transgene loci. The results show that various patterns of silencing appeared in the R2 generation at which most of the transgenes became homozygous and that they were inherited for five generations. In addition, silencing independently occurred in three generations and reversion to full expression was also found. Cloning of transgenes from a silenced L3.3 line demonstrated that this line carried two transgene loci: one carried an intact

Ltp2‐gus

gene and the other carried a rearranged transgene in which part of the

gus

gene was in the antisense orientation. Analysis of

gus

transcripts indicated that partial antisense RNA derived from the rearranged transgene was present in silenced lines and was polyadenylated but that it was absent in non‐silenced lines. RNA analyses suggested that the

Ltp2‐gus

silencing in the aleurone layer was post‐transcriptional and that it may be caused by interaction of partial antisense

gus

transcripts with normal sense transcripts. Possible involvement of antisense transcripts in post‐transcriptional silencing is discussed.
A minor form of starch branching enzyme in potato ( Solanum tuberosum L.) tubers has a major effect on starch structure: cloning and characterisation of multiple forms of SBE A
Authors: Jobling Stephen A.. , Schwall Gerhard P.. , Westcott Roger J.. , Sidebottom Christopher M.. , Debet Martine , Gidley Michael J.. , Jeffcoat Roger , Safford Richard 
Published: March 2003

SummaryFull length cDNAs encoding a second starch branching enzyme (SBE A) isoform have been isolated from potato tubers. The predicted protein has a molecular mass of 101 kDa including a transit peptide of 48 amino acids. Multiple forms of the SBE A gene exist which differ mainly in the length of a polyglutamic acid repeat at the C‐terminus of the protein. Expression of the mature protein in Escherichia coli demonstrates that the gene encodes an active SBE. Northern analysis demonstrates that SBE A mRNA is expressed at very low levels in tubers but is the predominant isoform in leaves. This expression pattern was confirmed by Western analysis using isoform specific polyclonal antibodies raised against E. coli expressed SBE A. SBE A protein is found predominantly in the soluble phase of tuber extracts, indicating a stromal location within the plastid. Transgenic potato plants expressing an antisense SBE A RNA were generated in which almost complete reductions in SBE A were observed. SBE activity in the leaves of these plants was severely reduced, but tuber activity was largely unaffected. Even so, the composition and structure of tuber starch from these plants was greatly altered. The proportion of linear chains was not significantly increased but the average chain length of amylopectin was greater, resulting in an increase in apparent amylose content as judged by iodine binding. In addition, the starch had much higher levels of phosphorous.
Tobacco retinoblastoma‐related protein phosphorylated by a distinct cyclin‐dependent kinase complex with Cdc2/cyclin D in vitro
Authors: Nakagami Hirofumi , Sekine Masami , Murakami Hiroko , Shinmyo Atsuhiko 
Published: March 2003

SummaryThe retinoblastoma (Rb) protein was originally identified as a product of a tumour suppressor gene that plays a pivotal role in regulating both the cell cycle and differentiation in mammals. The growth‐suppressive activity of Rb is regulated by phosphorylation with cyclin‐dependent kinase (CDK), and inactivation of the Rb function is one of the critical steps for transition from the G1 to the S phase. We report here the cloning of a cDNA (NtRb1) from Nicotiana tabacum which encodes a Rb‐related protein, and show that this gene is expressed in all the organs examined at the mRNA level. We have demonstrated that NtRb1 interacts with tobacco cyclin D by using yeast two‐hybrid and in vitro binding assays. In mammals, cyclin D can assemble with CDK4 and CDK6, but not with Cdc2, to form active complexes. Surprisingly, tobacco cyclin D and Cdc2 proteins can form a complex in insect cells, which is able to phosphorylate tobacco Rb‐related protein in vitro. Using immunoprecipitation with the anti‐cyclin D antibody, cyclin D can be found in a complex with Cdc2 in suspension‐cultured tobacco BY‐2 cells. These results suggest that the cdc2 gene modulates the cell cycle through the phosphorylation of Rb‐related protein by forming an active complex with cyclin D in plants.
The sax1 dwarf mutant of Arabidopsis thaliana shows altered sensitivity of growth responses to abscisic acid, auxin, gibberellins and ethylene and is partially rescued by exogenous brassinosteroid
Authors: Ephritikhine Geneviève , Fellner Martin , Vannini Candida , Lapous Danielle , Barbier‐Brygoo Hélène 
Published: March 2003

SummaryGenetic approaches using Arabidopsis thaliana aimed at the identification of mutations affecting events involved in auxin signalling have usually led to the isolation of auxin‐resistant mutants. From a selection screen specifically developed to isolate auxin‐hypersensitive mutants, one mutant line was selected for its increased sensitivity to auxin (× 2 to 3) for the root elongation response. The genetic analysis of sax1 (hypersensitive to abscisic acid and auxin) indicated that the mutant phenotype segregates as a single recessive Mendelian locus, mapping to the lower arm of chromosome 1. Sax1 seedlings grown in vitro showed a short curled primary root and small, round, dark‐green cotyledons. In the greenhouse, adult sax1 plants were characterized by a dwarf phenotype, delayed development and reduced fertility. Further physiological characterization of sax1 seedlings revealed that the most striking trait was a large increase (× 40) in ABA‐sensitivity of root elongation and, to a lesser extent, of ABA‐induced stomatal closure; in other respects, hypocotyl elongation was resistant to gibberellins and ethylene. These alterations in hormone sensitivity in sax1 plants co‐segregated with the dwarf phenotype suggesting that processes involved in cell elongation are modified. Treatment of mutant seedlings with an exogenous brassinosteroid partially rescued a wild‐type size, suggesting that brassinosteroid biosynthesis might be affected in sax1 plants. Wild‐type sensitivities to ABA, auxin and gibberellins were also restored in sax1 plants by exogenous application of brassinosteroid, illustrating the pivotal importance of the BR‐related SAX1 gene.
Distribution of fungal endophyte genotypes in doubly infected host grasses
Authors: Wille Patrick A. , Aeschbacher Roger A. , Boller Thomas 
Published: March 2003

SummaryFungal endophytes of the genus Epichloë live intercellulary in above ground plant parts of many pooid ‘grasses of the temperate regions. The associations are characterized by single genotype entities since a given host individual normally contains a single endophyte genotype. They can persist over the life span of the hosts. This study examines whether two fungal genotypes can co‐exist within a host plant, and how fungal genotypes are distributed within a host in the case of double infections. We selected four Epichloë bromicola strains that we identified as unique genotypes through RAPD‘ analysis. Young Bromus erectus plants, derived from callus cultures, were artificially inoculated with all possible double‐strain mixtures of these fungal genotypes. For identification of fungal genotypes in planta, we designed genotype‐specific primer pairs that flanked size‐variable loci in the fungal genomes. Diagnostic PCR revealed that only one fungal genotype was present in most inoculated plants, but double infections were also observed with a frequency of 8% of all infected plants. Subsequent analyses of individual tillers of doubly infected plants revealed that, in a given tiller, both the leaf‐blade and the leaf‐sheath were colonized with only one endophyte genotype. Tillers without any detectable fungal DNA were also observed. Thus, co‐existence of multiple endophyte genotypes within a single host plant is governed by mutual exclusion at the tiller level.
Ethylene‐regulated gene expression in tomato fruit: characterization of novel ethylene‐responsive and ripening‐related genes isolated by differential display
Authors: Zegzouti Hicham , Jones Brian , Frasse Pierre , Marty Christel , Maitre Béatrice , Latché Alain , Pech Jean‐Claude , Bouzayen Mondher 
Published: March 2003

SummaryDifferential display was used to isolate early ethylene‐regulated genes from late immature green tomato fruit in order to obtain a broader understanding of the molecular basis by which ethylene coordinates the ripening process. Nineteen novel ethylene‐responsive (ER) cDNA clones were isolated that fell into three classes: (i) ethylene up‐regulated (ii) ethylene down‐regulated, and (iii) transiently induced. Expression analysis revealed that ethylene‐dependent changes in mRNA accumulation occurred rapidly (15 min) for most of the ER clones. The predicted proteins encoded by the ER genes are putatively involved in processes as diverse as primary metabolism, hormone signalling and stress responses. Although a number of the isolated ER clones correspond to genes already documented in other species, their responsiveness to ethylene is described here for the first time. Among the ER clones sharing high homology with regulatory genes, ER43, a putative GTP‐binding protein, and ER50, a CTR1‐like clone, are potentially involved in signal transduction. ER24 is homologous to the multi‐protein bridging factor MBF1 involved in transcriptional activation, and finally, two clones are homologous to genes involved in post‐transcriptional regulation: ER49, a putative translational elongation factor, and ER68, a mRNA helicase‐like gene. Six ER clones correspond to as yet unidentified genes. The expression studies indicated that all the ER genes are ripening‐regulated, and, depending on the clone, show changes in transcript accumulation either at the breaker, turning, or red stage. Analysis of transcript accumulation in different organs indicated a strong bias towards expression in the fruit for many of the clones. The potential roles for some of the ER clones in propagating the ethylene response and regulating fruit ripening are discussed.