CITRUS EST SEQUENCING AND PROSPECTS FOR A HIGH-DENSITY MICROARRAY

¹ Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA

To improve the publically available database of ESTs for citrus, we are sequencing clones from 12 new cDNA libraries. Most libraries have been prepared from tissue of Washington navel orange, but some were prepared from other sweet oranges or other varieties more appropriate for particular traits. Our overall objective is to develop EST collections that contain genes expressed in a range of organs and environmental conditions. Libraries sequenced include vegetative shoot tips (meristems), phloem tissue challenged by CTV, fruit rind after cold acclimation, rind and pulp after postharvest treatment and cold storage, rind of young fruit after thrip feeding, rind of Clementine at separation stage, roots exposed to citrus nematode, flowers, ovaries, developing seeds, and embryogenic callus. About 2000 clones from each library will be sequenced bidirectionally. Sequences are then trimmed, annotated, and assembled. A new microcomputer EST browser program, HarvEST:Citrus was developed to facilitate distribution and use of these and all other public citrus EST sequences. Analyses to be presented include the number of EST sequences and unigenes available for citrus, proportion of sequences expressed in various libraries, and the frequency of polymorphisms within these sequences. Plans for development of a high-density microarray containing multiple alleles of all available citrus sequences will be discussed. Strategies for use of this array in developing a high-density map of citrus will be outlined.