Cloning and characterization of differentially expressed genes in imbibed dormant and afterripened Avena fatua embryos.

To analyze the patterns of gene expression associated with seed dormancy in wild oat (Avena fatua), we have isolated cDNA clones corresponding to genes that are differentially expressed in dormant and afterripened line M73 embryos. Gene transcripts of these clones were maintained in embryos of imbibed dormant caryopses, but declined rapidly in afterripened embryos after imbibition. GA3 treatment of dormant caryopses, which breaks dormancy, could lower the transcript levels in dormant embryos. When the germination of afterripened caryopses was inhibited by high temperature (35 degrees C), the decline in abundance of the transcripts in afterripened embryos was arrested. These genes were expressed to various degrees in water-stressed, but not in unstressed, 7-day-old seedlings. The expression of the genes was also ABA-inducible in afterripened embryos. The expression patterns in non-dormant line SH430 wild oat were similar to those of afterripened M73. DNA sequence analyses indicated that some of the cDNA clones encode LEA (late embryogenesis-abundant) proteins and aldose reductase. The significance of the expression of these genes in maintaining seed dormancy or longevity is discussed.