Terminal-repeat retrotransposons with GAG domain in plant genomes : a new testimony on the complex world of transposable elements

A novel structure of nonautonomous long terminal repeat (LTR) retrotransposons called terminal repeat with GAG domain (TR-GAG) has been described in plants, both in monocotyledonous, dicotyledonous and basal angiosperm genomes. TR-GAGs are relatively short elements in length (<4 kb) showing the typical features of LTR-retrotransposons. However, they carry only one open reading frame coding for the GAG precursor protein involved for instance in transposition, the assembly, and the packaging of the element into the virus-like particle. GAG precursors show similarities with both Copia and Gypsy GAG proteins, suggesting evolutionary relationships of TR-GAG elements with both families. Despite the lack of the enzymatic machinery required for their mobility, strong evidences suggest that TR-GAGs are still active. TR-GAGs represent ubiquitous nonautonomous structures that could be involved in the molecular diversities of plant genomes

Evidence d’une recombinaison génomique entre deux espèces de caféiers génétiquement éloignées : Coffea pseudozanguebariae Bridson et C. liberica var dewevrei De Wild et Th Dur

La recombinaison génomique entre deux espèces de caféiers génétiquement éloignées est étudiée dans le croisement interspécifique Coffea pseudozanguebariae x C. liberica var. dewevrei. A cet effet, des caractères morphologiques, la durée de la fructification, la teneur en caféine et la teneur en hétéroside sont évaluées chez les espèces parentales, les hybrides F1 et les descendants des backcross de première génération (BC1). Les espèces parentales ont des caractères très contrastés : les feuilles, les fruits et les graines sont de très petites tailles, et 1 à 8 fleurs s’observent par noeud chez l’espèce C.  pseudozanguebariae. Cependant chez C. liberica var. dewevrei lesdimensions sont deux fois plus importantes et le nombre de fleurs par noeud oscille entre 37 et 103. La fructification dure en moyenne 67 jours chez C. pseudozanguebariae contre 309 jours C. liberica var. dewevrei. Les graines de C. pseudozanguebariae sont dépourvues de caféine mais contiennent en retour une forte teneur en hétéroside. Au contraire chez C. liberica var. dewevrei les graines renferment de la caféine mais sont dépourvues d’hétéroside. Les plantes F1 se distinguent nettement des espèces parentales : leurs caractères morphologiques et la durée de fructification sont intermédiaires entre ceux des parents. Leurs graines contiennent à la fois de la caféine et de l’hétéroside contrairement aux parents. Chez les descendants des backcross de première génération, la diversité est considérable pour tous les caractères observés et forme un continuum entre les deux espèces. Parmi les plantes BC1, certaines ont une durée moyenne de fructification (180 jours) mais elles sont dépourvues de caféine ou d’hétéroside, contrairement aux F1 et aux espèces parentales. Leur présence démontre la survenue de recombinaisons inter et intra chromosomiques entre les génomes des deux espèces. Cette recombinaison laisse entrevoir l’opportunité et la possibilité de l’utilisation des ressources génétiques des caféiers pour l’amélioration des espèces cultivées.Mots clés : Coffea pseudozanguebariae, Coffea liberica var. dewevrei, ressource génétique, caféine, hétéroside, durée de fructification, recombinaison génomique

Inheritance of caffeine and heteroside contents in an interspecific cross between a cultivated coffee species Coffea liberica var dewevrei and a wild species caffeine-free C. pseudozanguebariae

Coffee species originating from Africa, in particular the two major cultivated species #C. arabica and #C. canephora, usually contain caffeine in their beans, whereas almost all Malagasy coffee species are caffeine-free. However, one wild coffee species #C. pseudozanguebariae, collected near the coast in south Kenya, is also caffeine-free. Beans of this species contain a specific heteroside diterpene (hereinafter referred to simply as heteroside) and give a bitter coffee beverage. We have investigated the inheritance of the caffeine and heteropside contents of the first and second generations of an interspecific cross between #C. pseudozanguebariae and #C. liberica var #dewevei, for which the caffeine content is about 1% dmb (dry matter basis). The caffeine content of F1 hybrids (0.2% dmb) was lower than the parental average (0.47% dmb). Caffeine and heteroside contents appeared to be under polygenic control with a strong genetic effect. Nevertheless, one major gene with two alleles seemed to be involved in the control of both compounds. Absence of caffeine was apparently controlled by one recessive gene. Heteroside content seemed to be controlled by one co-dominant gene, heterozygotes being intermediate between the two different groups of homozygotes. (Résumé d'auteur

Inheritance of caffeine and heteroside contents in an interspecific cross between a cultivated coffee species Coffea liberica var dewevrei and a wild species caffeine-free C. pseudozanguebariae

Coffee species originating from Africa, in particular the two major cultivated species #C. arabica and #C. canephora, usually contain caffeine in their beans, whereas almost all Malagasy coffee species are caffeine-free. However, one wild coffee species #C. pseudozanguebariae, collected near the coast in south Kenya, is also caffeine-free. Beans of this species contain a specific heteroside diterpene (hereinafter referred to simply as heteroside) and give a bitter coffee beverage. We have investigated the inheritance of the caffeine and heteropside contents of the first and second generations of an interspecific cross between #C. pseudozanguebariae and #C. liberica var #dewevei, for which the caffeine content is about 1% dmb (dry matter basis). The caffeine content of F1 hybrids (0.2% dmb) was lower than the parental average (0.47% dmb). Caffeine and heteroside contents appeared to be under polygenic control with a strong genetic effect. Nevertheless, one major gene with two alleles seemed to be involved in the control of both compounds. Absence of caffeine was apparently controlled by one recessive gene. Heteroside content seemed to be controlled by one co-dominant gene, heterozygotes being intermediate between the two different groups of homozygotes. (Résumé d'auteur

Inheritance of coffee bean sucrose content in the interspecific cross Coffea pseudozanguebariae X Coffea liberica 'dewevrei'

International audienc

Interspecific genetic linkage map, segregation distorsion and genetic conversion in coffee (Coffea sp.)

International audienc

Interspecific genetic linkage map, segregation distortion and genetic conversion in coffee (Coffea sp.)

An interspecific partial genetic linkage map of #Coffea sp. based on 62 backcross hybrids is presented. F1 hybrids were generated by a cross between the wild #C. pseudozanguebariae and the anciently cultivated #C. liberica var. #dewevrei (DEW) ; progeny were then derived from a backcross between F1 hybrid and DEW. The map construction consisted of a two-step strategy using 5.5 and 3.1 LOD scores revealed by simulation file. The map consisted of 181 loci : 167 amplified fragment length polymorphism (AFLP) and 13 radom fragment length polymorphism (RFLP) loci. The markers were assembled into 14 linkage groups, each with 4-31 markers covering 1,144 cM. Segregation distorsion was observed for 30% of all loci, in particular 3:1 and 1:3 ratios equally favouring each of the two parents. The existence of such ratios suggests genetic conversions events. This map also represents an initial step towards the detection of quantitative trait loci. (Résumé d'auteur

Effect of the seeds provenance and treatment on the germination rate and plants growth of four forest trees species of Cote d'Ivoire

The rapid rate of deforestation in Cote d'Ivoire has led to loss of plant species diversity and also threatens some commercial tree species with extinction. Some reforestation and afforestation has been completed. However, for some species, the numbers of surviving transplants has declined. Hence, it is necessary to develop properly adapted and resilient genotypes that can effectively support the programs of forest restoration. In this context we evaluated the effects of the provenances of seeds and of various treatments on the germination rates and on plant growth of four commercial trees species (Pycnanthus angolensis, Terminalia superba, Mansonia altissima and Pterygota macrocarpa). We analyzed these parameters for seeds of three provenances (Daloa, Akoupe and Daoukro) of four species and for thirty plants aged 6 months per provenance. Time to begin germination and time to reach maximum germination were similar among species, and were not influenced by either treatment or provenance. Untreated seeds and those soaked for 24 and 48 h in water at room temperature yielded the highest germination rates, irrespective of species or provenance. The one exception was P. angolensis, for which no germination was recorded. Within species, some provenances produced higher germination percentages than did others. No clear relationship was computed between the germination rate and the morphometric characteristics of the seeds which varied significantly between provenances. Plant growth and morphological variability also depended greatly on provenance. Genetic factors might be implicated, therefore provenance trials should be undertaken and evaluated. Furthermore, molecular analysis should be undertaken to confirm the implications of genetic factors and allow for genetic selection