Expressed sequence tags (ESTs) and simple sequence repeat (SSR) markers from octoploid strawberry (Fragaria x ananassa)

Abstract

Background: Cultivated strawberry (Fragaria x ananassa) represents one of the most valued fruit crops in the United States. Despite its economic importance, the octoploid genome presents a formidable barrier to efficient study of genome structure and molecular mechanisms that underlie agriculturally-relevant traits. Many potentially fruitful research avenues, especially large-scale gene expression surveys and development of molecular genetic markers have been limited by a lack of sequence information in public databases. As a first step to remedy this discrepancy a cDNA library has been developed from salicylate-treated, whole-plant tissues and over 1800 expressed sequence tags (EST's) have been sequenced and analyzed.

Results: A putative unigene set of 1304 sequences--133 contigs and 1171 singlets--has been developed, and the transcripts have been functionally annotated. Homology searches indicate that 89.5% of sequences share significant similarity to known/putative proteins or Rosaceae ESTs. The ESTs have been functionally characterized and genes relevant to specific physiological processes of economic importance have been identified. A set of tools useful for SSR development and mapping is presented.

Conclusion: Sequences derived from this effort may be used to speed gene discovery efforts in Fragaria and the Rosaceae in general and also open avenues of comparative mapping. This report represents a first step in expanding molecular-genetic analyses in strawberry and demonstrates how computational tools can be used to optimally mine a large body of useful information from a relatively small data set.

Figure 1

Strawberry EST characterization as derived from GO analyses. ESTs were assigned to GO categories based onA) Functional GO matches B) Process GO matches C) Component GO matches.