GENE-EXPRESSION DURING COLD-ACCLIMATION IN STRAWBERRY

To elucidate the molecular basis of cold acclimation in strawberry (Fr agaria x anannassa), we have begun studies to identify genes associate d with low temperature (LT) acclimation. Differential screening of a c DNA library prepared from cold-acclimated strawberry plants allowed us to isolate several: cDNAs showing differential expression at LT. Nort hern analysis showed that the transcript level of Fcor1 (Fragaria cold -regulated) peaked after 2 days of LT exposure while that of Fcor2 pea ked after 2 weeks. On the other hand, the level of Fcor3 transcript de creased within 24 hours of LT exposure and remained low during the 8 w eeks acclimation period. Fcor1 and Fcor2 are expressed in all tissues while Fcor3 is specific to leaves. The Fcor1-encoded protein has a com positional bias for leucine, isoleucine, glycine, proline and serine. This protein shares homology with the proteins encoded by blt101, a LT -responsive gene from barley, and ESI3, a gene induced by salt stress in Lophopyrum. The FCOR2 protein is rich in lysine, leucine, valine, a lanine and arginine, and shows no homology with any known gene product s. The partial Fcor3 cDNA clone encodes a polypeptide that shows a ver y high identity with the spinach PSI subunit V and with the PSI PsaG p olypeptide from barley. The level of Fcor1 transcript accumulation is correlated with the freezing tolerance of the strawberry cultivars use d in our study. This suggests that Fcor1 may be useful as a molecular marker to select for this trait in related species of the Rosaceae fam ily.