UC San Diego

FRUITFULL (FUL) is a member of the MADS box family of genes that is involved with promoting the growth of carpe valves after fertilization. In Arabidopsis thaliana, FUL plays a fundamental role in fruit development, as ful fruit fail to elongate and are indehiscent. FUL is typically expressed throughout the floral meristem and vasculature early on, with a notable "apical-basal expression gradient" that develops along valve tissue after fertilization. The particular distribution of FUL activity in valves is likely correlated to its function in valve development, with deviant expression patterns causing severe defects in fruit morphology. Though previous studies have identified a 3.9 kb promoter region capable of driving wild type-like FUL expression, little is known about individual regulatory motifs that are responsible for patterning this expression. A series of promoter-GUS fusions were generated that allows the comparison of FUL transcriptional activity when driven by different promoter elements. The SQUAMOSA promoter-Binding Protein (SBP) motif, located 2971 bp upstream the FUL start codon, was found to be crucial for FUL's valve- specific expression, though not sufficient in maintaining the WT-like bipolar expression gradient. Two perfect CArG- box motifs (located 2038 bp and 2512 bp upstream FUL ATG) redundantly regulate FUL expression, with the presence of at least one functional CArG-box necessary to initiate FUL transcription. Additionally, two auxin response elements (AuxREs) were identified at either end of the 3.9 kb promoter (641 bp and 3679 bp upstream FUL ATG) and function as negative regulators of FUL transcription