bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two adjacent nuclear genes are required for functional complementation of a chloroplast trans‐splicing mutant from Chlamydomonas reinhardtii
Authors: Balczun Carsten , Bunse Astrid , Hahn Daniela , Bennoun Pierre , Nickelsen Jörg , Kück Ulrich 
Published: August 2005

SummaryThe chloroplast tscA gene from Chlamydomonas reinhardtii encodes a co‐factor RNA that is involved in trans‐splicing of exons 1 and 2 of the psaA mRNA encoding a core polypeptide of photosystem I. Here we provide molecular and genetic characterization of the trans‐splicing mutant TR72, which is defective in the 3′‐end processing of the tscA RNA and consequently defective in splicing exons 1 and 2 of the psaA mRNA. Using genomic complementation, two adjacent nuclear genes were identified, Rat1 and Rat2, that are able to restore the photosynthetic growth of mutant TR72. Restoration of the photosynthesis phenotype, however, was successful only with a DNA fragment containing both genes, while separate use of the two genes did not rescue the wild‐type phenotype. This was further confirmed by using a set of 10 gene derivatives in complementation tests. The deduced amino acid sequence of Rat1 shows significant sequence homology to the conserved NAD+‐binding domain of poly(ADP‐ribose) polymerases of eukaryotic organisms. However, mutagenesis of conserved residues in this putative NAD+‐binding domain did not reveal any effect on restoration efficiency. Immunodetection analyses with enriched fractions of chloroplast proteins indicated that Rat1 is associated with chloroplast membranes. Using the yeast three‐hybrid system, we were able to demonstrate the specific binding of tscA RNA by the Rat1 polypeptide. We propose that the two nuclear factors Rat1 and Rat2 are involved in processing of chloroplast tscA RNA and in subsequent splicing of psaA exons 1 and 2.
Telomerase‐independent cell survival in Arabidopsis thaliana
Authors: Matthew Watson J. , Bulankova Petra , Riha Karel , Shippen Dorothy E. , Vyskot Boris 
Published: August 2005

SummaryTelomerase is the reverse transcriptase responsible for the maintenance of telomeric repeat sequences in most species that have been studied. Inactivation of telomerase causes telomere shortening and results in the loss of the telomere's protective function, which in mammals leads to cell‐cycle arrest and apoptosis. Experiments performed on Arabidopsis thaliana mutants lacking telomerase activity revealed their unusually high tolerance for genome instability. Here we present molecular and cytogenetic analysis of two cell lines (A and B) derived from seeds of late‐generation telomerase‐deficient A. thaliana. These cultures have survived for about 3 years and are still viable. However, neither culture has adapted mechanisms to maintain terminal telomeric repeats. One culture (B) suffers from severe growth irregularities and a high degree of mortality. Karyological analysis revealed dramatic genomic rearrangements, a large variation in ploidy, and an extremely high percentage of anaphase bridges. The second cell line (A) survived an apparent crisis and phenotypically appears wild‐type with respect to growth and morphology. Despite these indications of genome stabilization, a high percentage of anaphase bridges was observed in the A line. We conclude that the restructured chromosome termini provide the A line with partial protection from end‐joining repair activities, thus allowing normal growth.
Transgene‐triggered, epigenetically regulated ectopic expression of a flower homeotic gene pMADS3 in Petunia
Authors: Kapoor Meenu , Baba Akiko , Kubo Ken‐ichi , Shibuya Kenichi , Matsui Keisuke , Tanaka Yoshikazu , Takatsuji Hiroshi 
Published: August 2005

Summary pMADS3 is a class C floral homeotic gene of Petunia that is specifically expressed in stamens and carpels of developing flowers. We previously reported that introduction of a part of the pMADS3 genomic sequence silenced endogenous pMADS3 (sil‐pMADS3) in transgenic Petunia hybrida. Here we report that introduction of the same sequence triggers ectopic expression of endogenous pMADS3 in sepals, petals and leaves (ect‐pMADS3), accompanied by homeotic conversion of the floral organs and altered leaf morphology similar to that of an Arabidopsis curly leaf mutant. The occurrence of the ect‐pMADS3 phenotype depended on the presence of pMADS3 intron 2 in the transgenes. Occasionally, sil‐pMADS3 and ect‐pMADS3 phenotypes somatically interconverted. Some T1 progeny inherited their parent's pMADS3 expression pattern, while others switched from sil‐pMADS3 to ect‐pMADS3 and vice versa. Both phenotypes occasionally occurred even after the transgenes were segregated away. RT‐PCR analyses of ectopically expressed pMADS3 transcripts indicated that two pMADS3 alleles were often differently regulated. Furthermore, reciprocal crosses with untransformed Petunia indicated that pMADS3 alleles other than the one ectopically expressed in T0 plants were sometimes expressed ectopically in T1 plants: the paramutation‐like transmission of epigenetic regulation between alleles. We detected in the transformants aberrant transcripts, including sense and antisense pMADS3 intron 2 sequences of heterogeneous molecular sizes, irrespective of the pMADS3 phenotypes. We speculate on possible molecular mechanisms underlying these epigenetic phenomena.
Toc64 is not required for import of proteins into chloroplasts in the mossPhyscomitrella patens
Authors: Hofmann Nancy Rosenbaum , Theg Steven M. 
Published: August 2005

SummaryToc64 has been suggested to be part of the chloroplast import machinery inPisum sativum. A role for Toc64 in protein transport has not been established, however. To address this, we generated knockout mutants in the mossPhyscomitrella patensusing the moss's ability to perform homologous recombination with nuclear DNA.Physcomitrella patenscontains two genes that encode Toc64‐like proteins. Both of those proteins appear to be localized in the chloroplast. The double‐mutant plants were lacking Toc64 protein in the chloroplasts but showed no growth phenotype. In addition, these plants accumulated other plastid proteins at wild‐type levels and showed no difference from wild type inin vitroprotein import assays. These plants did have a slightly altered chloroplast shape in some tissues, however. The evidence therefore indicates that Toc64 proteins are not required for import of proteins inPhyscomitrella, but may point to involvement in the determination of plastid shape.
Editing of plastid RNA in Arabidopsis thaliana ecotypes
Authors: Tillich Michael , Funk Helena T. , Schmitz‐Linneweber Christian , Poltnigg Peter , Sabater Bartolomé , Martin Mercedes , Maier Rainer M. 
Published: August 2005

SummaryPost‐transcriptional maturation of plastid‐encoded mRNAs from land plants includes editing by making cytidine to uridine alterations at highly specific positions; this usually restores codon identities for conserved amino acids that are important for the proper function of the affected proteins. In contrast to the rather constant number of editing sites their location varies greatly, even between closely related taxa. Here, we experimentally determined the specific pattern of editing sites (the editotype) of the plastid genome of Arabidopsis thaliana ecotype Columbia (Col‐0). Based on phylogenetic analyses of plastid open reading frames, we identified 28 editing sites. Two editing events in the genes matK and ndhB seem to have evolved late during the evolution of flowering plants. Strikingly, they are embedded in almost identical sequence elements and seem to be phylogenetically co‐processed. This suggests that the two sites are recognized by the same trans‐factor, which could help to explain the hitherto enigmatic gain of editing sites in evolution. In order to trace variations in editotype at the subspecies level we examined two other A. thaliana accessions, Cape Verde Islands (Cvi‐0) and Wassilewskija (Ws‐2), for the Col‐0 editing sites. Both Cvi‐0 and Ws‐2 possess and process the whole set of editing sites as determined in Col‐0, but the consequences of RNA editing differ at one position between the ecotypes.
Rice NRR, a negative regulator of disease resistance, interacts with Arabidopsis NPR1 and rice NH1
Authors: Chern Mawsheng , Canlas Patrick E. , Fitzgerald Heather A. , Ronald Pamela C. 
Published: August 2005

SummaryArabidopsis NPR1/NIM1 is a key regulator of systemic acquired resistance (SAR), which confers lasting broad‐spectrum resistance. Over‐expression of Arabidopsis NPR1 or the NPR1 homolog 1 (NH1) in rice results in enhanced resistance to the pathogen Xanthomonasoryzae pv. oryzae (Xoo), suggesting the presence of a related defense pathway in rice. We investigated this pathway in rice by identifying proteins that interact with NH1. Here we report the isolation and characterization of a rice cDNA encoding a novel protein, named NRR (for negative regulator of resistance). NRR interacts with NPR1 in the NPR1‐interacting domain (NI25) consisting of 25 amino acids. NRR also interacts with NH1; however, NI25 was not sufficient for a strong interaction, indicating a difference between the rice and the Arabidopsis proteins. Silencing of NRR in rice had little effect on resistance to Xoo. When constitutively over‐expressed in rice, NRR affected basal resistance, age‐related resistance and Xa21‐mediated resistance, causing enhanced susceptibility to Xoo. This phenotype was correlated with elevated NRR mRNA and protein levels and increased Xoo growth. Over‐expression of NRR suppressed the induction of defense‐related genes. NRR:GFP (green fluorescent protein) protein was localized to the nucleus, indicating that NRR may act directly to suppress the activation of defense genes. The fact that NRR compromises Xa21‐mediated resistance indicates cross‐talk or overlap between NH1‐ and Xa21‐mediated pathways.
Improved transcriptional activators and their use in mis‐expression traps in Arabidopsis
Authors: Rutherford Stephen , Brandizzi Federica , Townley Helen , Craft Judith , Wang Yibing , Jepson Ian , Martinez Alberto , Moore Ian 
Published: August 2005

SummaryThe synthetic transcription factor LhG4 has been used in numerous mis‐expression studies in plants. We show that the sequence encoding the LhG4 activation domain, derived from Saccharomyces cerevisiae GAL4, contains several cryptic polyadenylation signals in Arabidopsis. The GAL4‐derived sequence was modified according to preferred Arabidopsis codon usage, generating LhG4AtO which was faithfully transcribed in Arabidopsis plants. In protoplasts, LhG4AtO achieved maximum transactivation of the pOp promoter with 10‐fold less input DNA than LhG4. The same methods were used to compare 10 other LhG4 derivatives that carried alternative natural or synthetic activation domains. Lh214 and Lh314, which contain synthetic activation domains comprising trimers of a core acidic activation domain, directed threefold more GUS expression from the pOp promoter with 20‐fold less input DNA than LhG4. In contrast, when expressed from the CaMV 35S promoter in transgenic plants carrying a pOp–GUS reporter, Lh214 and Lh314 yielded transformants with substantially lower GUS activities than other constructs including LhG4AtO and LhG4 which performed similarly. When incorporated into an enhancer‐trapping vector, however, LhG4AtO and Lh314 yielded enhancer traps with approximately twice the frequency of LhG4, suggesting that the modified activation domains offer improved performance when expressed from weaker transcription signals. To increase the number of LhG4 patterns available for mis‐expression studies, we describe a population of enhancer‐trap lines obtained with LhG4AtO in a pOp–GUS background. We show that enhancer‐trap lines can transactivate an unlinked pOp–green fluorescent protein (pOp‐GFP) reporter in the pattern predicted by staining for GUS activity.
Expression of floral MADS‐box genes in basal angiosperms: implications for the evolution of floral regulators
Authors: Kim Sangtae , Koh Jin , Yoo Mi‐Jeong , Kong Hongzhi , Hu Yi , Ma Hong , Soltis Pamela S. , Soltis Douglas E. 
Published: August 2005

SummaryThe ABC model of floral organ identity is based on studies of Arabidopsis and Antirrhinum, both of which are highly derived eudicots. Most of the genes required for the ABC functions in Arabidopsis and Antirrhinum are members of the MADS‐box gene family, and their orthologs are present in all major angiosperm lineages. Although the eudicots comprise 75% of all angiosperms, most of the diversity in arrangement and number of floral parts is actually found among basal angiosperm lineages, for which little is known about the genes that control floral development. To investigate the conservation and divergence of expression patterns of floral MADS‐box genes in basal angiosperms relative to eudicot model systems, we isolated several floral MADS‐box genes and examined their expression patterns in representative species, including Amborella (Amborellaceae), Nuphar (Nymphaeaceae) and Illicium (Austrobaileyales), the successive sister groups to all other extant angiosperms, plus Magnolia and Asimina, members of the large magnoliid clade. Our results from multiple methods (relative‐quantitative RT‐PCR, real‐time PCR and RNA in situ hybridization) revealed that expression patterns of floral MADS‐box genes in basal angiosperms are broader than those of their counterparts in eudicots and monocots. In particular, (i) AP1 homologs are generally expressed in all floral organs and leaves, (ii) AP3/PI homologs are generally expressed in all floral organs and (iii) AG homologs are expressed in stamens and carpels of most basal angiosperms, in agreement with the expectations of the ABC model; however, an AG homolog is also expressed in the tepals of Illicium. The broader range of strong expression of AP3/PI homologs is inferred to be the ancestral pattern for all angiosperms and is also consistent with the gradual morphological intergradations often observed between adjacent floral organs in basal angiosperms.
The transcription factor ATAF2 represses the expression of pathogenesis‐related genes in Arabidopsis
Authors: Delessert Christian , Kazan Kemal , Wilson Iain W. , Straeten Dominique Van Der , Manners John , Dennis Elizabeth S. , Dolferus Rudy 
Published: August 2005

SummaryATAF2, a member of the plant‐specific NAC‐domain transcription factor family, is highly induced in leaves at a wound site and is responsive to the wound‐related phytohormones methyl jasmonate and salicylic acid, but not to abscisic acid. Overexpression of ATAF2 leads to an increased biomass and yellowing of the leaves, but there is no obvious phenotype in two independent ATAF2 T‐DNA insertion lines. At the transcriptome level, ATAF2 overexpression resulted in repression of a number of pathogenesis‐related proteins. Conversely, four of these pathogenesis‐related transcripts were increased in both ATAF2 knock‐out lines. ATAF2 overexpressing plants showed a higher susceptibility to the soil‐borne fungal pathogen Fusarium oxysporum. Our results indicate that ATAF2 functions as a repressor of pathogenesis‐related proteins in Arabidopsis.
Tobacco plants respond to the constitutive expression of the tospovirus movement protein NSM with a heat‐reversible sealing of plasmodesmata that impairs development
Authors: Rinne Päivi L.H. , Boogaard Riki van den , Mensink Manon G.J. , Kopperud Cor , Kormelink Richard , Goldbach Rob , Schoot Chris van der 
Published: August 2005

SummaryViral infection often results in typical symptoms, the biological background of which has remained elusive. We show that constitutive expression of the NSM viral movement protein (MP) of tomato spotted wilt virus in Nicotiana tabacum is sufficient to induce severe, infection‐like symptoms, including pronounced deficiencies in root and shoot development. Leaves failed to expand and were arranged in a rosette due to the absence of internode elongation. Following the sink–source transition they accumulated excessive amounts of starch and developed fusing chlorotic patches in the mesophyll, resembling virus‐induced chlorotic lesions. Eventually, the leaves became entirely white and brittle. With a combination of techniques, including photosystem II quantum‐yield measurements, iontophoresis of symplasmic tracers, bombardment with pPVX.GFP and double immunolabelling it was shown that these symptoms correlated with the obstruction of NSM‐targeted mesophyll plasmodesmata (Pd) in source tissues by depositions of 1,3‐β‐D‐glucan (GLU) or callose. Temperature‐shift treatments (TST; 22→32°C), known to abolish chlorotic local lesions, also abolished the chlorotic ‘superlesions’ of transgenic plants and rescued plant development, by restoring the transport capacity of Pd through the action of 1,3‐β‐D‐glucanase (GLU‐h) or callase. Return of these elongated, TST‐recovered plants to 22°C reintroduced superlesions and arrested shoot elongation, resulting in the formation of a rosette of clustered leaves at the shoot tip. Collectively, this indicates that the symptoms of NSM plants are self‐inflicted and due to a basal defence response that counteracts prolonged interference of the MP with Pd functioning. This type of defence may also play a role in the formation of symptoms during viral infection.
The stylar 120 kDa glycoprotein is required for S‐specific pollen rejection in Nicotiana
Authors: Nathan Hancock C. , Kent Lia , McClure Bruce A. 
Published: August 2005

SummaryS‐RNase participates in at least three mechanisms of pollen rejection. It functions in S‐specific pollen rejection (self‐incompatibility) and in at least two distinct interspecific mechanisms of pollen rejection in Nicotiana. S‐specific pollen rejection and rejection of pollen from Nicotiana plumbaginifolia also require additional stylar proteins. Transmitting‐tract‐specific (TTS) protein, 120 kDa glycoprotein (120K) and pistil extensin‐like protein III (PELP III) are stylar glycoproteins that bind S‐RNase in vitro and are also known to interact with pollen. Here we tested whether these glycoproteins have a direct role in pollen rejection. 120K shows the most polymorphism in size between Nicotiana species. Larger 120K‐like proteins are often correlated with S‐specific pollen rejection. Sequencing results suggest that the polymorphism primarily reflects differences in glycosylation, although indels also occur in the predicted polypeptides. Using RNA interference (RNAi), we suppressed expression of 120K to determine if it is required for S‐specific pollen rejection. Transgenic SC N. plumbaginifolia × SI Nicotiana alata (S105S105 or SC10SC10) hybrids with no detectable 120K were unable to perform S‐specific pollen rejection. Thus, 120K has a direct role in S‐specific pollen rejection. However, suppression of 120K had no effect on rejection of N. plumbaginifolia pollen. In contrast, suppression of HT‐B, a factor previously implicated in S‐specific pollen rejection, disrupts rejection of N. plumbaginifolia pollen. Thus, S‐specific pollen rejection and rejection of N. plumbaginifolia pollen are mechanistically distinct, because they require different non‐S‐RNase factors.
Overexpression of COL9, a CONSTANS‐LIKE gene, delays flowering by reducing expression of CO and FT in Arabidopsis thaliana
Authors: Cheng Xiao‐Fei , Wang Zeng‐Yu 
Published: August 2005

Summary CONSTANS (CO) is an important floral regulator in the photoperiod pathway, integrating the circadian clock and light signal into a control for flowering time. It is known that CO promotes flowering in Arabidopsis under long‐day conditions. CONSTANS‐LIKE 9 (COL9) is a member of the CONSTANS‐LIKE gene family, encoding a nuclear protein. The expression of COL9 is regulated by the circadian clock in the photoperiod pathway and is detected in various organs. Unexpectedly, overexpression of COL9 in transgenic Arabidopsis resulted in delayed flowering, while co‐suppression lines and a transferred DNA (T‐DNA) knockout line showed earlier flowering under long‐day conditions. Overexpression of COL9 did not enhance the late‐flowering phenotype in a co mutant background. Double overexpressors produced by overexpression of CO in COL9 transgenic lines showed an early flowering phenotype similar to single CO overexpressors. The pattern of oscillation of a number of circadian‐associated genes remained unchanged in the COL9 transgenic lines. Compared with wild‐type plants, the abundance of CO and FLOWERING LOCUS T (FT) mRNA was reduced in the COL9 overexpression lines. Our results indicate that COL9 is involved in regulation of flowering time by repressing the expression of CO, concomitantly reducing the expression of FT and delaying floral transition.
The Normal Electrocardiogram of the Unanaesthetized Competition ‘Spanish Pouler’ Pigeon (Columba livia gutturosa)
Authors: Lopez Murcia M. M. , Bernal L. J. , Montes A. M. , Garcia Martinez J. D. , Ayala I. 
Published: August 2005

SummaryThis investigation was carried out on 64 healthy adult competition pigeons (Spanish Poulers) to determine reference values of electrocardiographic parameters in standard lead II; a comparative study between males and females was also performed to find changes in the electrocardiographic patterns related to sex. P wave was positive and monophasic; PR segment depression was present in 64% of records; the QRS pattern obtained was in most cases of the rS type, followed by the QS configuration. ST slurring (absence of ST) was observed in 47% of records and the mean electrical axis was in all cases negative. Statistically significant differences related to sex were found for P‐wave, R‐wave and T‐wave amplitudes, showing the males have greater amplitudes than females, associated with the increase of cardiac tissue mass. No sex‐related differences were found in heart rate and mean electrical axis.
Cytologic Features of Testicular Tumours in Dog
Authors: Masserdotti C. , Bonfanti U. , De Lorenzi D. , Tranquillo M. , Zanetti O. 
Published: August 2005

SummaryIn this paper, we report on our experience of cytology of fine needle biopsies performed on 92 dogs with testicular tumours during the period from 1998 to 2002. Cytological diagnosis was consistent with seminoma in 20 cases, sertolioma in 16 cases, Leydig cell tumours in 50 cases and mastocytoma in one case. Five cases could not be diagnosed by cytology. Cytological observations were confirmed after surgery by histopathological examination in 87 cases. Cytology provided a sensitivity of 95% for seminoma, 88% for sertolioma and 96% for Leydig cell tumours. The specificity was 100% for all three tumour types. In our experience cytology of fine needle aspirations of testicular tumours is a very reliable technique.
Persistent Truncus Arteriosus in a 6‐year‐old Cat
Authors: Nicolle A. P. , Tessier‐Vetzel D. , Begon E. , Sampedrano C. Carlos , Pouchelon J.‐L. , Chetboul V. 
Published: August 2005

SummaryTruncus arteriosus (TA) was diagnosed in a 6‐year‐old neutered female domestic short‐haired cat by two‐dimensional and M‐mode echocardiography, colour flow imaging and spectral Doppler examinations. The lesion was characterized by a single large artery originating from the right ventricle. A single ascending aorta and a single pulmonary trunk arose from the common arterial trunk. The residual pulmonary trunk immediately split into left and right branches. The lesion was identified as a type I (TA). This case is of interest because it is the first reported echo‐Doppler description of such a malformation in felines, and because of the age of the cat at the time of diagnosis.