CHARACTERIZATION OF CDNA CLONES FOR DIFFERENTIALLY EXPRESSED GENES INEMBRYOS OF DORMANT AND NONDORMANT AVENA-FATUA L CARYOPSES

The molecular regulation of seed dormancy was investigated using diffe rential display to visualize and isolate cDNAs representing differenti ally expressed genes during early imbibition of dormant and nondormant Avena fatua L. embryos. Of about 3000 cDNA bands examined, 5 cDNAs hy bridized with mRNAs exhibiting dormancy-associated expression patterns during the first 48 h of imbibition, while many more nondormancy-asso ciated cDNAs were observed. Dormancy-associated clone AFD1 hybridized with a 1.5 kb mRNA barely detectable in dry dormant and nondormant emb ryos that became more abundant in dormant embryos after 24 h of imbibi tion. Clone AFD2 hybridized with two mRNAs, a 1.3 kb message constitut ively expressed in dormant and nondormant embryos and a 0.9 kb message present at higher levels in dormant embryos after 3 h of imbibition. Nondormancy-associated clones AFN1, AFN2 and AFN3 hybridized with 1.5 kb, 1.7 kb and 1.1 kb mRNAs, respectively, that were more abundant in nondormant embryos during imbibition. Expression patterns of some mRNA s in dormant embryos induced to germinate by GA(3) treatment were diff erent than water controls, but were not identic al to those observed i n nondormant embryos. DNA sequence analysis revealed 76% sequence iden tity between clone AFN3 and a Citrus sinensis glutathione peroxidase-l ike cDNA, while significant sequence similarities with known genes wer e not found for other clones. Southern hybridization analyses showed t hat all clones represent low (1 to 4) copy number genes.