CITRUS EST COLLECTION AND FUNCTIONAL STUDIES USING A GENOME-WIDE CITRUS cDNA MICROARRAY

Spanish Citrus Genomics Project (http://citrusgenomics.iata-ibmcp-ivia.upv.es)

Instituto de Biologia Molecular y Celular de Plantas, Avda. de los naranjos s/n, Valencia, 46022, Spain

Instituto de Agroquimica y Tecnologia de Alimentos, Apdo. 73, Burjasot, Valencia, 46100, Spain

Instituto Valenciano de Investigaciones Agrarias, Carretera Moncada-Náquera Km 4.5, Moncada, Valencia, 46113, Spain

A Citrus functional genomics project (CFGP) focused in Clementine mandarine, the most important cultivar of the spanish industry, has been initiated in Spain with the objective to develop genomic tools for genetic improvement of Citrus cultivars. To achieve this objective, a collection of Citrus ESTs has been generated from cDNA libraries covering a wide range variety of biological and environmental conditions. Specific attention has been paid to different aspects involved in the production process and fruit quality such as: vegetative growth, flowering, fruit set and maturation, responses to biotic and abiotic stresses, and post-harvest processes. To gain insight into the expression patterns and potential role of all these genes, a first cDNA microarray with nearly 11.000 CFGP clones representing around 7000 UniGenes has been produced. The array contains probes from 14 different cDNA libraries of the CFGP EST collection, giving this new tool a genome-wide scope. This microarray is being used to characterize the Citrus transcriptome in different biological conditions of interest, thus allowing the identification of Citrus genes involved in the response to these conditions. A genomic library has also been generated that will contribute to characterize relevant genes (completion of sequences, intron distribution, identification of promoters). In this communication, a description of the EST collection and details of microarray design and quality control, as well as first experiments using this array for analysing different stress responses and developmental stages, are presented. This work has been carried out by several research groups from the Institutes listed above.