FIL2, AN EXTRACELLULAR LEUCINE-RICH REPEAT PROTEIN, IS SPECIFICALLY EXPRESSED IN ANTIRRHINUM FLOWERS

The expression of the Antirrhinum gene FIL2 is affected in mutants of the homeotic transcription factor DEFICIENS. Northern and Western blot analyses showed that FIL2 in wild-type Antirrhinum flowers is express ed weakly in the petals and more abundantly in the reproductive organs ; the gene is active in the filaments and anthers of stamens, and in t he stigma and transmitting tissue of the carpels. The FIL2 protein is glycosylated with high mannose type glycan chains and is located in th e middle lamella of the extracellular matrix. The amino acid sequence contains 10 tandem repeats, the composition of which is similar to the Leucine-Rich Repeat (LRR) motif found in mammals, Drosophila and yeas t. The possibility that FIL2 might be a component of a cellular signal ling mechanism, involving LRR-mediated protein-protein interactions is discussed.