GENOTYPE AND ENVIRONMENT INTERACT TO CENTRAL DORMANCY AND DIFFERENTIAL EXPRESSION OF THE VIVIPAROUS-1 HOMOLOG IN EMBRYOS OF AVENA-FATUA

Embryo dormancy is a reversible developmental state during which germi nation is repressed. In this study, inbred lines of Avena fatua were u sed to analyse the influence of genotype and environment on the dorman t phenotype, and on expression of the homologue of the maize transcrip tion factor VIVIPAROUS 1 (afVP 1). The cDNA for afVP 1 was cloned from mature embryos. Analysis of the predicted protein sequence revealed a high degree of similarity to other VP 1/ABI 3-related transcription f actors, in particular in four regions previously shown to be highly co nserved, including the BR2 region that has been shown to interact with several classes of sequence-specific DNA binding proteins. The potent ial of imbibed mature embryos for dormancy was analysed and shown to b e determined primarily by genotype and secondarily by previous environ mental experience of the mature seed acting on embryo genotype. Under all conditions studied, expression of afVP 1 and the A. fatua homologu e of Pm (shown in maize to be regulated by VP 1 during embryo maturati on) were positively correlated with the dormant phenotype, whereas exp ression of A. fatua AMY-related RNAs was negatively correlated with do rmancy (in barley AMY 6-4 has been shown to be repressed by VP 1). Exp ression of afVP 1 RNA was also shown in the dry seed to be positively correlated with the length of time required for seeds of the inbred li nes to after-ripen. These results suggest new functions for the VP 1 t ranscription factor family in the control of dormancy-related processe s in embryo cells of mature seeds, and the up-regulation of afVP 1 and afEm RNAs in the dormant state suggests that they are regulated by a switching mechanism in the mature seed that shows some aspects of reve rsibility.