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Discovery of stress tolerance genes using global collections of rice mutants : [C2.5].

Pereira A., Hirochika H., Guiderdoni E., Lorieux M., Verdier V., Ishitani M., Lu T., Jin D., Zhang Q., Leung H.. 2005. In : IRRI. 5th International Rice Genetics Symposium (A platform for exploring developments in rice genetics and their applications) and 3rd International Symposium of Rice Functional Genomics. Abstract. Manila : IRRI, p. 21-21. International Rice Genetics Symposium. 5, 2005-11-19/2005-11-23, Manille (Philippines).

The International Rice Functional Genomics Consortium (IRFGC), has been working together to collaborate on setting up a functional genomics platform to systematically study rice gene functions. International efforts since the last few years have produced rice mutant resources that are a powerful functional genomics tool to identify the function of the sequenced rice genes. Within a Generation Challenge Program project the consortium works together towards the identification of genes that can contribute to a phenotype of resistance/tolerance to abiotic/biotic stresses. A list of over five hundred candidate rice Stress Associated Genes (SAGs) was collated based on genes revealed by microarray analysis induced under various stresses, as well as known functions from other plants. In a reverse genetic strategy, we are using sequence-indexed knockout mutant resources developed by the rice international community to identify insertions in the target stress associated genes, from among a collection of over sixty thousand insertion sites in the rice genome (http://orygenesdb.cirad.fr/). These include Tos17 transposons, heterologous Ac-Ds transposons and T-DNA inserts that are identified by available flanking sequence tags (FSTs) that are positioned on the complete genome sequence. In addition an available TILLING population is used to supplement the mutant coverage, and also provide non-transgenic stocks for field testing. To resolve gene redundancy, gain-of-function overexpression lines are being generated by transformation of appropriate constructs, and available activation tag populations will also be accessed for overexpression mutants. To facilitate novel gene discovery a forward genetics mutant screen is being carried out with insertion tagged genotypes that have been sequence indexed, thus aiding their further analysis. The selected collection of mutant genotypes is being phenotyped for drought and disease stress parameters in greenhouse and field-based screens. Genotypes with altered stress tolerance phenotypes will be tested for other abiotic/biotic stresses. Whole genome microarray analysis will be conducted to identify the downstream genes and characterize the stress response mechanism involved. The genes with validated function for stress resistance in rice are then a source for comparative genetics studies in other crop plants.

Mots-clés : oryza sativa

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