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L'objectif principal du programme « Corifor, corridors entre îlots forestiers » était de déterminer dans quelle mesure la fragmentation actuelle des paysages agit sur les relations liant la composition (floristique et biologique) des peuplements forestiers avec la structure (superficie et distance inter-isolat) d'un environnement forestier fragmenté.- Les résultats apportent des éléments de compréhension sur l’évolution des paysages fragmentés du Grand Sud calédonien et des recommandations pour la restauration en vue de la création de corridors écologiques opérationnels, notamment dans un contexte minier.- La définition de la classe « forêt dense humide » au sens réglementaire est discutée, dans l’objectif de renforcer les mesures de protection des forêts.- Enfin sont suggérées 6 règles majeures qu’il conviendrait de suivre pour améliorer la gestion des forêts du Grand Sud calédonien.

L'objectif principal du projet CoRiFor est de déterminer dans quelle mesure la fragmentation actuelle des paysages agit sur les relations liant la composition (floristique et biologique) des peuplements forestiers avec la structure (superficie et distance inter-isolat) d'un environnement forestier fragmenté.

Lipoxygenases (LOXs) are enzymes responsible for lipid peroxidation processes during plant defence responses to pathogen infection. Jasmonates are lipid-derived signals that mediate plant stress responses with chloroplastic LOXs implicated in the biosynthesis of oxylipins like jasmonic acid (JA). Hypersensitive reaction (HR) cell death of cotton to the incompatible race 18 of Xanthomonas campestris pathovar malvacearum (Xcm) is associated with 9S-lipoxygenase activity and expression of a 9-LOX GhLOX1. Here, we report the cloning of cotton (Gossypium hirsutum L.) LOX gene GhLOX2. Sequence analysis showed that GhLOX2 is a putative 13-LOX with a chloroplast-transit peptide in the amino acid terminus. GhLOX2 was found to be significantly expressed in the first hour of Xcm-induced HR. Investigation into LOX signalization on cotyledons incubated with methyl-jasmonate (MeJA) or infiltrated with salicylic acid (SA) or ethylene (ET) revealed that the first two treatments induced GhLOX2 gene expression. Our results show that GhLOX2 gene expression occurred at the stage of the HR prior biochemical events previously highlighted. The role that GhLOX2 may have in the defence strategy of cotton to Xcm is discussed regarding the HR.

Several ethylene-response factor (ERF) transcription factors are believed to play a crucial role in the activation of plant defence responses, but little is known about the relationships between the diversity of this family and the functions of groups or individual ERFs in this process. In this study, 200 ERF genes from the unigene cotton database were identified. Conserved amino acid residues and phylogeny reconstruction using the AP2 conserved domain suggest that the classification into 10 major groups used for Arabidopsis and rice is applicable to the cotton ERF family. Based on in silico studies, we predict that group IX ERF genes in cotton are involved in jasmonate (JA), ethylene (ET) and pathogen responses. To test this hypothesis, we analysed the transcript profiles of the group IXa subfamily in the regulation of specific resistance to Xanthomonas campestris pathovar malvacearum. The expression of four members of group IXa was induced on challenge with X. campestris pv. malvacearum. Furthermore, the expression of several ERF genes of group IXa was induced synergistically by JA in combination with ET, suggesting that the encoded ERF proteins may play key roles in the integration of both signals to activate JA- and ET-dependent responses.

We compared rice transgenic plants obtained by #Agrobacterium$-mediated and particle bombardment transformation by carrying out molecular analyses of the T0, T1 and T2 transgenic plants. #Oryza sativa japonica$ rice (c.v. Taipei 309) was transformed with a construct (pWNHG) that carried genes coding for neomycin phosphotransferase (nptII), hygromycin phosphotransferase (Hyg(sup)r), and Beta-glucuronidase (GUS). Thirteen and fourteen transgenic lines produced via either method were selected and subjected to molecular analysis. Based on our data, we could draw the following conclusions. Average gene copy numbers of the three transgenes were 1.8 and 2.7 for transgenic plants obtained by #Agrobacterium$ and by particle bombardment, respectively. The percentage of transgenic plants containing intact copies of foreign genes, especially non-selection genes, was higher for #Agrobacterium$-mediated transformation. GUS gene expression level in transgenic plants obtained from #Agrobacterium$-mediated transformation was more stable overall the transgenic plant lines obtained by particle bombardment. Most of the transgenic plants obtained from the two transformation systems gave a Mendelian segregation pattern of foreign genes in T1 and T2 generations. Co-segregation was observed for lines obtained from particle bombardment, however, that was not always the case for T1 lines obtained from #Agrobacterium$-mediated transformation. Fertility of transgenic plants obtained from #Agrobacterim$-mediated transformation was better. In summary, the #Agrobacterium$-mediated transformation is a good system to obtain transgenic plants with lower copy number, intact foreign gene and stable gene expression, while particle bombardment is a high efficiency system to produce large number of transgenic plants with a wide range of gene expression. (Résumé d'auteur)

Fourteen different primers were used to amplify DNA from selfed progenies of 117 diploid plants regenerated from haploid cell suspension protoplasts of rice (cv. Miara). This survey, which permitted to generate 69 different major fragments in control Miara plants as well as in protoclone DNA, did not reveal genetic change among protoclones compared to the donor variety except independent amplification of an additional fragment in nearly half of the lines by two 10-mers. This polymorphism in the protoclonal population was attributed to natural intravarietal variation among the donor plants which have been collected to establish the microscope-callus suspension culture. However, polymorphism could not be detected in calluses grown from cell clumps collected in the 21-month old cell suspension. This apparent lack of tissue culture-induced polymorphism at the molecular level contrasts with the results of a previous field evaluation of the progenies which exhibited both wide range and high frequency morphological changes. These observations highlight the absence of apparent relationship between morphological variation and molecular changes. The interest of RAPDs as a convenient method to test genetic integrity of the regenerants, that would preclude the need for further field evaluation, is discussed. (Résumé d'auteur)

Des clones cDNA de Manioc (#Manihot esculenta$ Crantz) ont été utilisés pour détecter le polymorphisme de longueur des fragments de resriction (RFLP) dans une collection de germplasm de manioc conservée en culture #in vitro$ au centre ORSTOM de Montpellier. La collection se compose principalement de cultivars africains de #M. esculenta$, ainsi que de quelques #M.glaziovii$ Mueller Von Argau and #M. caerulescens$ Pohl, et de quelques hybrides interspécifiques de #M. esculenta$ x #M. glaziovii$. Les sondes cDNA mettent à jour des niveaux de polymorphisme significatifs à la fois à l'intérieur et entre les espèces ; ce qui est suffisant pour créer des dendogrammes indiquant la diversité génétique à l'intérieur de la collection. (Résumé d'auteur)

Analyse des modifications protéiques associées aux concentrations du 2,4-D exogène au cours de la morphogénèse des cals de palmier à huile

La régénération du palmier à huile passe par une phase d'embryogenèse somatique où deux types de cals peuvent être utilisés. Un type de cal conduit à une malformation des inflorescences des plantes régénérées, l'autre permet une régénération conforme. Une analyse des profils protéiques par électrophorèse monodimensionnelle permet d'identifier pour trois clones étudiés un marqueur protéique discriminant les deux types de cals.