Characterization of FaSPT, a SPATULA gene encoding a bHLH transcriptional factor from the non-climacteric strawberry fruit.

The involvement of basic-helix-loop-helix (bHLH) transcription factors in essential physiological and developmental processes is well established. Although a lot of animal bHLH proteins were characterized functionally, much less bHLHs of plant origin have been studied so far. Using a cDNA-AFLP approach, a ripening-related SPATULA gene was identified from strawberry fruit (Fragaria × ananassa Duch.), which encodes a bHLH protein. It is an orthologue of an Arabidopsis SPATULA protein, which has an important role in carpel and fruit development. Our experiments revealed that FaSPT is repressed by auxin in green fruits, and shows different expression patterns in receptacles at various stages of fruit ripening by ethylene treatment. Moreover, we applied a reverse genetic tool to elucidate the in planta function of FaSPT in early fruit development. To our knowledge, this work is the first report for the characterization of a SPATULA gene from a non-climacteric fruit.