CONSERVED RY-REPEATS MEDIATE TRANSACTIVATION OF SEED-SPECIFIC PROMOTERS BY THE DEVELOPMENTAL REGULATOR PVALF

Transcription of genes DLEC2 and PHS beta is specifically and coordina tely regulated during maturation of Phaseolus embryos. Over-expression of the seed-specific factor PvALF in cotyledon cells results in trans activation of either promoter. PvALF is related to the VP1 protein of maize, which transactivates gene expression via G-boxes, Sph elements and AT-rich sequences. We used deletions and base substitutions in the DLEC2 and PHS beta promoters to demonstrate that several conserved RY -repeats were necessary for PvALF induction of both genes. A comprehen sive mutational and transactivation analysis was used to define functi onally the sequence of the DLEC2 repeat RY3 as (G)/(C)CATGCXX(G)/(C). We also found that an interaction between RY3 and the 3'-flanking tetr anucleotide CCAC increased PvALF transactivation. A preferred spacing and phasing requirement for the RY3 and CCAC motifs suggested the poss ibility of interactions between cellular factors that recognize either element. The high conservation of Sph-RY motifs in seed-specific prom oters from monocots and dicots indicates that organ and temporal speci fication by factors similar to VP1 and PvALF is common among seed plan ts.