Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie最新文献

{"title":"A naked plant-specific RNA ten-fold smaller than the smallest known viral RNA: the viroid","authors":"Ricardo Flores","doi":"10.1016/S0764-4469(01)01370-1","DOIUrl":"10.1016/S0764-4469(01)01370-1","url":null,"abstract":"<div><p>Viroids are subviral plant pathogens at the frontier of life. They are solely composed by a single-stranded circular RNA of 246–401 nt with a compact secondary structure. Viroids replicate autonomously when inoculated into their host plants and incite, in most of them, economically important diseases. In contrast to viruses, viroids do not code for any protein and depend on host enzymes for their replication, which in some viroids occurs in the nucleus and in others in the chloroplast, through a rolling-circle mechanism with three catalytic steps. Quite remarkably, however, one of the steps, cleavage of the oligomeric head-to-tail replicative intermediates to unit-length strands, is mediated in certain viroids by hammerhead ribozymes that can be formed by their strands of both polarities. Viroids induce disease by direct interaction with host factors, the nature of which is presently unknown. Some properties of viroids, particularly the presence of ribozymes, suggest that they might have appeared very early in evolution and could represent ˈliving fossilsˈ of the precellular RNA world that presumably preceded our current world based on DNA and proteins.</p></div>","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 943-952"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01370-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75404633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Concepts actuels sur la pathogénie chez les bactéries phytopathogènes","authors":"Christian Boucher,&nbsp;Stéphane Genin,&nbsp;Matthieu Arlat","doi":"10.1016/S0764-4469(01)01375-0","DOIUrl":"10.1016/S0764-4469(01)01375-0","url":null,"abstract":"<div><p>What are the molecular determinants that make a bacterium a plant pathogen? In the last 10–20 years, important progress has been made in answering this question. In the early 20th century soon after the discovery of infectious diseases, the first studies of pathogenicity were undertaken. These early studies relied mostly on biochemistry and led to the discovery of several major pathogenicity determinants, such as toxins and hydrolytic enzymes which govern the production of major disease symptoms. From these pioneering studies, a simplistic view of pathogenicity arose. It was thought that only a few functions were sufficient to transform a bacterium into a pathogen. This view rapidly changed when modern techniques of molecular genetics were applied to analyse pathogenicity. Modern analyses of pathogenicity determinants took advantage of the relatively simple organization of the haploid genome of pathogenic bacteria. By creating non-pathogenic mutants, a large number of genes governing bacterium–host interactions were identified. These genes are required either for host colonization or for the production of symptoms. Even though the role of motility and chemotaxis in these processes is still unclear, it is clear that a strong attachment of <em>Agrobacterium</em> to plant cells is a prerequisite for efficient plant transformation and disease. Other important pathogenicity factors identified with a molecular genetic approach include hydrolytic enzymes such as pectinases and cellulases which not only provide nutrients to the bacteria but also facilitate pathogen invasion into host tissues. The precise role of exopolysaccharide in pathogenicity is still under discussion, however it is has been established that it is crucial for the induction of wilt symptoms caused by <em>Ralstonia solanacearum</em>. Trafficking of effector proteins from the invading bacterium into the host cell emerged recently as a new central concept. In plant pathogenic bacteria, protein translocation takes place through the so-called ‘type III secretion machinery’ encoded by <em>hrp</em> genes in the bacterium. These genes are present in representatives of all the major groups of Gram negative plant pathogenic bacteria except <em>Agrobacterium</em>. Most of these genes have counterparts in pathogens of mammals (including those of human) and they also play a central role in pathogenicity. Additionally, recent evidence suggests that a ‘type IV secretion machinery’ injects bacterial proteins into host cells. This machinery, originally found to be involved in the transfer of t-DNA from <em>Agrobacterium</em> into plant cells, was recently shown to translocate pathogenicity proteins in pathogens of mammals such as <em>Helicobacter pylori</em> and <em>Brucella.</em> Discovery of the trafficking of proteins from the pathogen into host cells revolutionized our conception of pathogenicity. First, it rather unexpectedly established the conservation of basic pathogenicity strategies ","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 915-922"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01375-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86479122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plantes et agents pathogènes, une liaison raffinée et dangereuse : l’exemple des champignons","authors":"Marie-Thérèse Esquerré-Tugayé","doi":"10.1016/S0764-4469(01)01374-9","DOIUrl":"10.1016/S0764-4469(01)01374-9","url":null,"abstract":"<div><p>Plant–fungus interactions are highly diverse, either being beneficial to the host plant such as those leading to mycorhizal symbiosis, or very detrimental when leading to severe diseases. Since the beginning of agriculture, improvement of plant resistance to pathogens has remained a major challenge. Breeding for resistance, first conducted empirically in the past centuries, was then performed on a more theoretical basis after the statement of heredity laws by Mendel at the end of the XIXth century. As a result, most cultivated species contain various cultivars whose resistance or susceptibility to a given pathogen species depend on their interaction with various races of that pathogen. Such highly specific race-cultivar systems are particularly suited for understanding the molecular dialogue which underlies compatible (host susceptible/pathogen virulent) or incompatible (host resistant/pathogen avirulent) interactions. During the twentieth century, one of the major events that paved the way for future research was the statement by Flor 〚1946, 1947〛 of the gene-for-gene concept. Studying inheritance of the disease phenotype in the interaction between flax and <em>Melampsora lini</em> he showed that resistance in the host and avirulence in the pathogen are dictated by single dominant genes which correspond one to one, i.e. one resistance gene for one avirulence gene. The fact that incompatibility may depend on the presence of only one resistance (<em>R</em>) gene in the host and one avirulence (<em>Avr</em>) gene in the pathogen was fully confirmed about 40 years later. Molecular genetics and complementation experiments have allowed to isolate numerous <em>R</em> and <em>Avr</em> genes from various plant–pathogen systems, and to verify the gene-for-gene concept. These studies have enlightened the elicitor/receptor concept, formerly introduced to account for the specificity of the compatible and incompatible interactions. The present knowledge of <em>R</em> and <em>Avr</em> genes also allows to predict how such genes have evolved and how they could be used to improve disease resistance. At the beginning of the twenty first century, this remains a major challenge in view of the severe losses caused by pests and pathogens to most crops on the earth.</p></div>","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 899-903"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01374-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79744911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Découverte du premier virus, le virus de la mosaïque du tabac : 1892 ou 1898 ?","authors":"Hervé Lecoq","doi":"10.1016/S0764-4469(01)01368-3","DOIUrl":"10.1016/S0764-4469(01)01368-3","url":null,"abstract":"<div><p>Two scientists contributed to the discovery of the first virus, <em>Tobacco mosaic virus</em>. Ivanoski reported in 1892 that extracts from infected leaves were still infectious after filtration through a Chamberland filter-candle. Bacteria are retained by such filters, a new world was discovered : filterable pathogens. However, Ivanovski probably did not grasp the full meaning of his discovery. Beijerinck, in 1898, was the first to call ‘virus’, the incitant of the tobacco mosaic. He showed that the incitant was able to migrate in an agar gel, therefore being an infectious soluble agent, or a ‘contagium vivum fluidum’ and definitively not a ‘contagium fixum’ as would be a bacteria. Ivanovski and Beijerinck brought unequal but decisive and complementary contributions to the discovery of viruses. Since then, discoveries made on <em>Tobacco mosaic virus</em> have stood out as milestones of virology history.</p></div>","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 929-933"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01368-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77282769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EXPLICATION PHYSIQUE","authors":"M Du Hamel","doi":"10.1016/S0764-4469(01)01366-X","DOIUrl":"10.1016/S0764-4469(01)01366-X","url":null,"abstract":"","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 875-891"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01366-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84920931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Champignons des plantes : les premiers agents pathogènes reconnus dans l’histoire des sciences","authors":"Frantz Rapilly","doi":"10.1016/S0764-4469(01)01373-7","DOIUrl":"10.1016/S0764-4469(01)01373-7","url":null,"abstract":"<div><p>The eighteenth century is the beginning of the scientific emergence of plant pathology. Naturalists disproved spontaneous generation, meteorological and supernatural origins of plant diseases. It is necessary to explain plant alterations and to find possibilities of control to reduce significant losses of yield and to limit famine. In 1728, the words ‘plant parasite’,’plant disease’, and ‘epidemics’ were used for the first time. In 1755, the first seed treatment and, in 1805 the first description of a whole cycle of plant disease were proposed. In the nineteenth century much work on bunt and rusts of wheat, potato downy mildew, and grape vine powdery mildew established the scientific status of plant pathology. A retrospective analysis of these early developments shows a very good concordance with Koch’s postulate published one century later.</p></div>","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 893-898"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01373-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85991523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stimulation des défenses naturelles des plantes","authors":"Olivier Klarzynski,&nbsp;Bernard Fritig","doi":"10.1016/S0764-4469(01)01371-3","DOIUrl":"10.1016/S0764-4469(01)01371-3","url":null,"abstract":"<div><p>Some defense mechanisms of plants are of the passive type while others are induced after perception of the pathogenic microorganism (very specific gene-for-gene recognition) or of microbial components (non specific elicitors). These recognition events trigger an array of plant signals and a cascade of signalling pathways which activate a battery of metabolic alterations responsible for the observed induced resistance. These include the stimulated production of low molecular weight molecules with antibiotic activity, cell wall reinforcement by deposition and cross-linking of various macromolecules, and accumulation of a wide range of PR (‘pathogenesis-related’) proteins that exhibit direct and/or indirect antimicrobial activities. The present studies aim to caracterize natural elicitors or design chemical messengers capable of triggering an array of plant defense responses. Treatments of plants with elicitors could be an alternative strategy of crop protection with a more satisfactory preservation of the environment.</p></div>","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 953-963"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01371-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84938162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Introduction à la séance commune consacrée aux agents pathogènes des plantes : découverte, pathogénie, problèmes de société","authors":"Josy Bové","doi":"10.1016/S0764-4469(01)01367-1","DOIUrl":"10.1016/S0764-4469(01)01367-1","url":null,"abstract":"","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 10","pages":"Pages 873-874"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01367-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75605118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An oleate desaturase and a suppressor loci direct high oleic acid content of sunflower (Helianthus annuus L.) oil in the Pervenets mutant","authors":"Séverine Lacombe ,&nbsp;François Kaan ,&nbsp;Sandrine Léger ,&nbsp;André Bervillé","doi":"10.1016/S0764-4469(01)01353-1","DOIUrl":"10.1016/S0764-4469(01)01353-1","url":null,"abstract":"<div><p>All the 〚HOAC〛 lines derived from the Pervenets mutant carry a specific RFLP (oleHOS) revealed by an oleate desaturase cDNA used as a probe. The 〚LO〛 (linoleic) genotypes do not carry oleHOS, but another allele: oleLOR. We studied 〚HOAC〛 heredity in two segregating populations. In an F2 population, the 〚HOAC〛 trait co-segregated with oleHOS. In a recombinant inbred line F6 population, all 〚HOAC〛 RI lines carried oleHOS. The RI lines carrying oleHOS were either 〚LO〛 or 〚HOAC〛. The absence of 〚HOAC〛 RI lines with oleLOR eliminated the occurrence of a recombination event between the locus carrying oleHOS and the locus carrying Pervenets allele. The 〚HOAC〛 trait is due to 2 independent loci: the locus carrying oleHOS allele and another locus. One allele at this other locus may suppress the effect of oleHOS allele on the 〚HOAC〛 trait. The existence of this suppressor allele has only been suggested for sunflower.</p></div>","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 9","pages":"Pages 839-845"},"PeriodicalIF":0.0,"publicationDate":"2001-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01353-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77157329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Root growth and lignification of two wheat species differing in their sensitivity to NaCl, in response to salt stress","authors":"Najoua Jbir ,&nbsp;Wided Chaïbi ,&nbsp;Saïda Ammar ,&nbsp;Ahmed Jemmali ,&nbsp;Abdelkader Ayadi","doi":"10.1016/S0764-4469(01)01355-5","DOIUrl":"10.1016/S0764-4469(01)01355-5","url":null,"abstract":"<div><p>Application of a 100-mM NaCl salt stress to wheat seedlings of a salt-tolerant (<em>Triticum durum</em> var. Ben Béchir) and a salt-sensitive (<em>Triticum aestivum</em> var. Tanit) species decreases the fresh and dry weights of roots especially in the salt-sensitive species, and slightly increases the ratio of dry to fresh weight, especially in the salt-resistant species. All peroxidase activities are increased by salt stress, the water-soluble peroxidase activity being increased much more in the salt-sensitive than in the salt-tolerant species, while the opposite result is observed with the cell-wall peroxidase activity. Some water-soluble peroxidases have been hypothesised to have auxin oxidase activity (which might explain the effect observed on the root biomass), while the cell-wall peroxidases would be involved in lignification. Histochemical observation confirms a more intense lignification in the root cells of the salt-tolerant species compared to the sensitive species, under the effect of NaCl.</p></div>","PeriodicalId":100306,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie","volume":"324 9","pages":"Pages 863-868"},"PeriodicalIF":0.0,"publicationDate":"2001-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0764-4469(01)01355-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75637665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}