Grape expansins, VvEXPA14 and VvEXPA18 promote cell expansion in transgenic Arabidopsis plant

We herein report the molecular characterization of grape expansins, VvEXPA14 and VvEXPA18. VvEXPA14 and VvEXPA18 transcription was detected in grape berries at 2 weeks post flowering and their expression was upregulated during growth phase I, the period of rapid berry expansion. Experiments using VvEXPA14:GFP or VvEXPA18: GFP fusion proteins demonstrated that both expansins were localized at cell wall, suggesting that both expansins may function on cell wall. Transgenic tobacco cells overexpressing VvEXPA14 or VvEXPA18 exhibited cell expansion. In addition, VvEXPA14- or VvEXPA18-overexpressing Arabidopsis plants showed primary root elongation associated with cell expansion. VvEXPA14 overexpression enlarged rosette leaves in Arabidopsis transgenic plants, although the height of the plants remained unchanged. Since plant expansin play role in cell wall loosing and softening, these results underscore the possibility that VvEXPA14 and VvEXPA18 are involved in cell expansion and plant growth.