Generation and analysis of expressed sequence tags from almond ( Prunus dulcis Mill.) pistils

Abstract

Large-scale single-pass sequencing of expressed sequence tags (ESTs) can give a global picture of the genes involved in the development and function of organs and tissues. Almond (Prunus dulcis Mill. syn. Amygdalus communis L. var. dulcis) is a self-incompatible fruit tree of the family Rosaceae. As an attempt to examine the transcripts expressed during pistil development, we randomly selected and partially sequenced over 1,000 clones from a cDNA library of almond pistils. Analysis of the ESTs using the NCBI non-redundant protein database revealed that 456 (~45.4%) have significant similarity to protein coding sequences in the database. Among the 549 cDNAs with no similarity to known protein sequences, 56 clones have significant similarity to nucleotide sequences registered in the databases. Sequences were assembled using StackPACK and the estimated number of genes identified was 716: 121 contigs and 595 singletons. Only eight of the unique cDNA clones correspond to previously isolated gene sequences of P. dulcis. After functional classification of almond ESTs, "stress resistance and defense" and "protein synthesis and processing" ESTs were found to be the most numerous. Our EST analysis provides a first picture of the numerous almond genes potentially involved in pistil development. It also contributes to our knowledge about gene expression patterns in pistils while providing an extensive reservoir for gene cloning and genetic mapping in almond and other related fruit trees.