Molecular identification of proline-rich protein genes induced during root formation in grape (Vitis vinifera L.) stem cuttings

Vegetative reproduction relies on the initiation of new plant organs in response to environmental changes. The rapid formation of roots, and ultimately whole plants, from stem cuttings of grape (Vitis vinifera L.) provides a useful system to investigate the physiological and molecular basis of organ initiation during vegetative reproduction. In the present study the differential RNA display technique was employed to identify two genes, VvPRP1 and VvPRP2, that are induced in stem cuttings of grape during rooting. Each of these genes encodes a distinct type of proline-rich protein that is related to different groups of putative cell wall proteins, and their expression is rapidly induced in stem segments within 6 h after severing. Further, each gene's transcript becomes most concentrated in the basal portion of the stem segment in the region of new root formation. Induction of these genes is not significantly enhanced by indole-3-acetic acid (IAA) treatment, and the expression of the VvPRP1 gene, but not the VvPRP2 gene, is wound-inducible. These results suggest that these VvPRP genes play an important role in the initiation of new roots on grape stem cuttings, perhaps by altering the cell wall mechanical properties to enable root emergence.