Development of an expressed sequence tag (EST) library for Medicago sativa

Expressed sequence tag (EST) libraries for alfalfa (Medicago sativa L.) wer e developed from two cDNA populations derived from full sibs from a cross b etween 'Riley' and the glandular-haired germplasm, KS224. Sibs where sorted into two populations based on the presence or lack of both long- and short -stalked glandular hairs. Glandular hairs have been associated with resista nce to pests in alfalfa. Each cDNA population was enriched using the second population as the driver in cDNA subtraction, The differential expression of the majority of the randomly selected cDNAs was verified via reverse Nor thern hybridization. However, not all sequenced cDNAs were detectable using reverse Northerns, possibly due to their low relative abundance. Fifty-fiv e percent of the ESTs sequenced from the eglandular-haired pool, versus 40% ,. for the glandular-haired cDNA pool, had homology to earlier identified p lant genes. When ESTs were compared with the EST database alone, 64% of the 210 glandular-hai red ESTs that had no sequence homology to the non-redund ant database, also were unique to all plant ESTs sequenced to date. This wa s twice the percentage for eglandular-haired ESTs. The systematic analysis of ESTs from this study serves as a tool to identify genes regulating devel opment of glandular trichomes and the resistance to insects associated with them. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.