Gene flow among different taxonomic units: evidence from nuclear and cytoplasmic markers in Cedrus plantation forests.

Hybridization and introgression are important natural evolutionary processes that can be successfully investigated using molecular markers and open- and controlled-pollinated progeny. In this study, we collected open-pollinated seeds from Cedrus atlantica, Cedrus libani and C. libani x C. atlantica hybrids from three French-plantation forests. We also used pollen from C. libani and Cedrus brevifolia to pollinate C. atlantica trees. The progeny were analyzed using three different types of molecular markers: RAPDs, AFLPs and cpSSRs. Chloroplast DNA was found to be paternally inherited in Cedrus from the progeny of controlled-crosses. Heteroplasmy, although possible, could not be undoubtedly detected. There was no indication of strong reproductive isolating barriers among the three Mediterranean Cedrus taxa. Gene flow between C. atlantica and C. libani accounted for 67 to 81% of viable open-pollinated seedlings in two plantation forests. We propose that Mediterranean Cedrus taxa should be considered as units of a single collective species comprising two regional groups, North Africa and the Middle East. We recommend the use of cpSSRs for monitoring gene flow between taxa in plantation forests, especially in areas where garden specimens of one species are planted in the vicinity of selected seed-stands and gene-conservation reserves of another species.

[Coronary sinus in rhythmology]. / Le sinus coronaire en rythmologie.

Because of its complex anatomical structure and its position in the heart, the coronary sinus, plays a major role in many diagnostic and therapeutic EP procedures. Anatomy of the coronary sinus is crucial during biventricular pacemaker implantation. Mapping of the coronary sinus is of primary importance during left-sided accessory pathway evaluation and ablation. More recently, the coronary sinus musculature and its connections to left and right atrium and to left ventricle have been identified as playing an important role in various types of supraventricular arrhythmias.

[Hyperandrogenism and pregnancy]. / Hyperandrogénie et grossesse.

Normal pregnancy is associated with high circulating levels of total testosterone explained by an increment of the synthesis of testosterone-estradiol-binding globulin (TeBG), and an increase in plasma free-testosterone and androstenedione levels. Protection mechanisms against maternal and fetal virilization conterbalance this biological hyperandrogenism. However, these mechanisms of protection may be overtaken leading to a maternal virilization during pregnancy. Acne, temporal balding, clitoromegaly and hirsutism could be observed. The most important point is to evaluate the risk of virilization of a female fetus. Earlier the hyperandrogenism occurs during pregnancy, higher is the risk of fetal virilization. The first step consists to identify a gestational exposition to androgen, the second to find an organic etiology. The most common etiologies include ovarian luteomas and theca-lutein-cysts. Others ovarian diseases (arrhenoblastomas, Krukenberg tumors and polycystic ovary syndrome) and adrenal causes are much more rare. Unfortunately, there is no treatment available during pregnancy.

Catheter ablation of typical atrial flutter: a randomized comparison of 2 methods for determining complete bidirectional isthmus block.

BACKGROUND: Complete bidirectional isthmus conduction block (CBIB) was initially assessed by sequential detailed activation mapping at both sides of the ablation line during proximal coronary sinus and anteroinferior right atrium pacing. Mapping only the ablation line ("on-site" atrial potential analysis) was recently reported as a means of CBIB identification. The study was designed to compare these 2 techniques prospectively regarding the diagnosis of CBIB. METHODS AND RESULTS: In 76 consecutive patients (mean age, 63.4+/-10.5 years), typical atrial flutter ablation was performed using either the activation mapping technique (group I) or on-site atrial potential analysis (group II). Criteria for CBIB using on-site atrial potential analysis was the recording of parallel, widely spaced double atrial potentials along the ablation line. The CBIB criterion was retrospectively searched using the alternative technique at the end of the procedure. In successful patients, the mean radiofrequency delivery duration was longer in group II (845+/-776 versus 534+/-363 s; P:=0.03). On-site, clear-cut, widely spaced double atrial potentials and activation mapping suggesting CBIB were concomitantly observed in only 47 patients (54%), and ambiguous/atypical double potentials were recorded in 31 patients (39%). CONCLUSIONS: Although feasible, the on-site atrial potential analysis seemed to be inferior to the classic activation mapping technique, mainly because of the ambiguity of electrogram interpretation along the ablation line. However, when combined with the activation mapping technique, it provided additional information regarding isthmus conduction properties in some cases. Therefore, optimally, both methods should be used concomitantly.

[New invasive cartography techniques in electrophysiology]. / Les nouvelles techniques de cartographie invasive en électrophysiologie.

Fulguration, a widely used technique in the 80s, has been replaced by radiofrequency ablation. The limited and better controlled intra-cardiac lesions obtained by this method allowed the elimination of a large number of tachycardias with a high success rate. However, there are many arrhythmias, particularly at the atrial level, which are so complex that a limited analysis at a number of points of endocardial recording is inadequate. Recently, a number of systems has been introduced which considerably increased the acuity of observation of arrhythmias and the efficacy of their ablation. First of all, there are improved techniques of classical electrophysiological recording. Then, new systems of temporo-spatial recordings were developed and are described in this article. These use computer systems and enable particularly reliable and detailed approaches to cardiac anatomy and electrophysiology. However, the optimal use of these techniques can only be in specialised centres, by highly trained cardiologists in classical electrophysiology, for which they are complementary to rather than substitute for.

Characterization of an Arabidopsis thaliana receptor-like protein kinase gene activated by oxidative stress and pathogen attack.

An Arabidopsis thaliana cDNA clone that encodes a putative receptor-like protein kinase gene (At-RLK3) was characterized. The deduced 667-amino acid protein consists of an amino-terminal signal sequence, an extracellular domain, a single transmembrane domain, and a cytoplasmic domain with characteristics of serine/threonine protein kinase. Because of the original features of its extracellular domain, the At-RLK3 protein is a member of a new class of receptor-like protein kinases. The At-RLK3 gene is present as a single copy within the Arabidopsis genome and its transcripts are detected in root, stem, leaf and flower. In cultured cells, the At-RLK3 gene is activated upon oxidative stress and salicylic acid treatment. In plants, the gene appears to be differentially regulated during various plant-pathogen interactions: upon inoculation with strains of Pseudomonas syringae pv. tomato harboring or not, different avr genes, At-RLK3 transcripts accumulate transiently at similar levels during both compatible and incompatible interactions. This gene is, however, preferentially expressed during the incompatible interaction induced by the soil-borne vascular bacteria, Ralstonia solanacearum. The involvement of At-RLK3 in signal transduction pathways during pathogen attack is discussed.

Abscisic acid-independent and abscisic acid-dependent regulation of proline biosynthesis following cold and osmotic stresses in Arabidopsis thaliana.

The role of the phytohormone abscisic acid (ABA) in the regulation of proline synthesis was investigated by following the expression of the At-P5S and At-P5R proline biosynthesis genes in Arabidopsis thaliana wild type, in an ABA-deficient aba1-1 mutant as well as in ABA-insensitive abi1-1 and abi2-1 mutants after ABA, cold and osmotic stress treatments. In wild-type and in ABA mutant seedlings, 50 microM ABA or osmotic stress treatment triggered expression of At-P5S, whereas At-P5R accumulation was scarcely detectable. Expression of either gene was mediated by endogenous ABA since transcript levels were similar in wild-type and in ABA-deficient mutant plants. Proline accumulated to a greater extent after osmotic stress than upon ABA or cold treatment. Thus, ABA-treated abi1-1 mutant plants accumulated less proline than the ABA-treated wild type. Upon salt stress, proline accumulated to a lesser extent in aba1-1 and abi1-1 mutant plants, suggesting an indirect role of ABA on proline accumulation during salt adaptation of the plant. These results indicate that the expression of the genes of the proline biosynthetic pathway is ABA independent upon cold and osmotic treatments, although their expression can be triggered by exogenously applied ABA. However, the endogenous ABA content may affect proline accumulation upon salt stress, suggesting post-transcriptional control of proline biosynthesis in response to NaCl.

Plant cyclins: a unified nomenclature for plant A-, B- and D-type cyclins based on sequence organization.

The comparative analysis of a large number of plant cyclins of the A/B family has recently revealed that plants possess two distinct B-type groups and three distinct A-type groups of cyclins. Despite earlier uncertainties, this large-scale comparative analysis has allowed an unequivocal definition of plant cyclins into either A or B classes. We present here the most important results obtained in this study, and extend them to the case of plant D-type cyclins, in which three groups are identified. For each of the plant cyclin groups, consensus sequences have been established and a new, rational, plant-wide naming system is proposed in accordance with the guidelines of the Commission on Plant Gene Nomenclature. This nomenclature is based on the animal system indicating cyclin classes by an upper-case roman letter, and distinct groups within these classes by an arabic numeral suffix. The naming of plant cyclin classes is chosen to indicate homology to their closest animal class. The revised nomenclature of all described plant cyclins is presented, with their classification into groups CycA1, CycA2, CycA3, CycB1, CycB2, CycD1, CycD2 and CycD3.

Isolation, characterization, and chromosomal location of a gene encoding the delta 1-pyrroline-5-carboxylate synthetase in Arabidopsis thaliana.

A full-length cDNA and the corresponding At-P5S gene encoding the first enzyme of the proline biosynthetic pathway, the delta 1-pyrroline-5-carboxylate (P5C) synthetase, were isolated in Arabidopsis thaliana. The At-P5S cDNA encodes a protein of 717 amino acids showing high identity with the P5C synthetase of Vigna aconitifolia. Strong homology is also found at the N-terminus to bacterial and yeast gamma-glutamyl kinase and at the C-terminus to bacterial gamma-glutamyl phosphate reductase. Putative ATP- and NAD(P)H-binding sites are suggested in the At-P5S protein. The transcribed region of the At-P5S gene is 4.8 kb long and contains 20 exons. Southern analysis suggests the presence of only one At-P5S gene in the A. thaliana genome mapped at the bottom of the chromosome two. Expression analysis of At-P5S in different organs reveals abundant At-P5S transcripts in mature flowering plant. Rapid induction of the At-P5S gene followed by accumulation of proline was observed in NaCl-treated seedlings suggesting that At-P5S is osmoregulated.

Isolation of a full-length mitotic cyclin cDNA clone CycIIIMs from Medicago sativa: chromosomal mapping and expression.

Cyclins in association with the protein kinase p34cdc2 and related cyclin-dependent protein kinases (cdks) are key regulatory elements in controlling the cell division cycle. Here, we describe the identification and characterization of a full-length cDNA clone of alfalfa mitotic cyclin, termed CycIIIMs. Computer analysis of known plant cyclin gene sequences revealed that this cyclin belongs to the same structural group as the other known partial alfalfa cyclin sequences. Genetic segregation analysis based on DNA-DNA hybridization data showed that the CycIIIMs gene(s) locates in a single chromosomal region on linkage group 5 of the alfalfa genetic map between RFLP markers UO89A and CG13. The assignment of this cyclin to the mitotic cyclin class was based on its cDNA-derived sequence and its differential expression during G2/M cell cycle phase transition of a partially synchronized alfalfa cell culture. Sequence analysis indicated common motifs with both the A- and B-types of mitotic cyclins similarly to the newly described B3-type of animal cyclins.

Activation of the cell cycle machinery and the isoflavonoid biosynthesis pathway by active Rhizobium meliloti Nod signal molecules in Medicago microcallus suspensions.

We have shown that treatment of Medicago microcallus suspensions with the cognate Rhizobium meliloti Nod signal molecule NodRm-IV(C16:2,S) can modify gene expression both qualitatively and quantitatively. At concentrations of 10(-6) - 10(-9) M, this host specific plant morphogen but not the inactive non-sulfated molecule stimulated cell cycle progression as indicated by the significantly enhanced thymidine incorporation, elevated number of S phase cells, increase in kinase activity of the p34cdc2-related complexes and enhancement of the level of expression of several cell cycle marker genes, the histone H3-1, the cdc2Ms and the cyclin cycMs2. The presented data suggest that at least part of the physiological role of the Nod factor may be linked to molecular events involved in the control of the plant cell division cycle. In situ hybridization experiments with antisense H3-1 RNA probe indicated that only certain cells of the calli were able to respond to the Nod factor. High (10(-6) M) but not low (10(-9) M) concentrations of the active Nod factors induced the expression of the isoflavone reductase gene (IFR), a marker gene of the isoflavonoid biosynthesis pathway in most callus cells. Our results indicate that Medicago cell responses to the Nod signal molecules can be investigated in suspension cultures.

Identification of two alfalfa early nodulin genes with homology to members of the pea Enod12 gene family.

In a search for plant genes expressed during early symbiotic interactions between Medicago sativa and Rhizobium meliloti, we have isolated and characterized two alfalfa genes which have strong sequence similarity to members of the Enod12 gene family of Pisum sativum. The M. sativa genes, MsEnod12A and B, encode putative protein products of 8066 Da and 12849 Da, respectively, each with a signal sequence at the N-terminus followed by a repetitive proline-rich region. Based on their expression during the initial period of nodule development, MsEnod12A and B are alfalfa early nodulin genes.