Metabolic pathways in tropical dicotyledonous albuminous seeds: Coffea arabica as a case study

The genomic era facilitates the understanding of how transcriptional networks are interconnected to program seed development and filling. However, to date, little information is available regarding dicot seeds with a transient perisperm and a persistent, copious endosperm. Coffea arabica is the subject of increasing genomic research and is a model for nonorthodox albuminous dicot seeds of tropical origin.The aim of this study was to reconstruct the metabolic pathways involved in the biosynthesis of the main coffee seed storage compounds, namely cell wall polysaccharides, triacylglycerols, sucrose, and chlorogenic acids. For this purpose, we integrated transcriptomic and metabolite analyses, combining real-time RT-PCR performed on 137 selected genes (of which 79 were uncharacterized in Coffea) and metabolite profiling.Our map-drawing approach derived from model plants enabled us to propose a rationale for the peculiar traits of the coffee endosperm, such as its unusual fatty acid composition, remarkable accumulation of chlorogenic acid and cell wall polysaccharides.Comparison with the developmental features of exalbuminous seeds described in the literature revealed that the two seed types share important regulatory mechanisms for reserve biosynthesis, independent of the origin and ploidy level of the storage tissue

The 'PUCE CAFE' Project: the First 15K Coffee Microarray, a New Tool for Discovering Candidate Genes correlated to Agronomic and Quality Traits

Background: Understanding the genetic elements that contribute to key aspects of coffee biology will have an impact on future agronomical improvements for this economically important tree. During the past years, EST collections were generated in Coffee, opening the possibility to create new tools for functional genomics. Results: The "PUCE CAFE" Project, organized by the scientific consortium NESTLE/IRD/CIRAD, has developed an oligo-based microarray using 15,721 unigenes derived from published coffee EST sequences mostly obtained from different stages of fruit development and leaves in Coffea Canephora (Robusta). Hybridizations for two independent experiments served to compare global gene expression profiles in three types of tissue matter (mature beans, leaves and flowers) in C. canephora as well as in the leaves of three different coffee species (C. canephora, C. eugenoides and C. arabica). Microarray construction, statistical analyses and validation by Q-PCR analysis are presented in this study. Conclusion: We have generated the first 15 K coffee array during this PUCE CAFE project, granted by Genoplante (the French consortium for plant genomics). This new tool will help study functional genomics in a wide range of experiments on various plant tissues, such as analyzing bean maturation or resistance to pathogens or drought. Furthermore, the use of this array has proven to be valid in different coffee species (diploid or tetraploid), drastically enlarging its impact for high-throughput gene expression in the community of coffee research

La glutathion peroxydase du latex d'Hevea brasiliensis. Caractérisation et implications physiologiques

Tous les organismes vivants sont sensibles aux formes toxiques de l'oxygène. Cependant, H2O2, forme la plus stable, peut être décomposée dans le cytosol des laticifères d'H. brasiliensis par plusieurs enzymes dont une glutathion peroxydase (GPx) qui possède une masse moléculaire de 40 plus ou moins 5 kDa. L'éthylène employé ponctuellement pour stimuler la production de latex n'a pas d'effet significatif sur l'activité spécifique de l'enzyme. Cependant, l'accélération du métabolisme induite par un nombre croissant de stimulations éthyléniques augmente cette activité. La GPx est fonctionnelle dans un cytosol filtré dépourvu de protéine. La forte affinité de l'enzyme pour H2O2 et les teneurs de glutathion réduit in situ laissent penser que l'enzyme est responsable d'une détoxication efficace du H2O2 dans le late