A Plasma Membrane Intrinsic Protein Gene OfPIP2 Involved in Promoting Petal Expansion and Drought Resistance in Osmanthus fragrans

<i>Osmanthus fragrans</i>, a native to China, is renowned as a highly popular gardening plant. However, this plant faces significant challenges from drought stress, which can adversely affect its flowering. In this study, we found that the plasma membrane-localized gene <i>OfPIP2</i> exhibited a substantial upregulation during the flowering stages and in response to drought stress. GUS staining has illustrated that the <i>OfPIP2</i> promoter can drive GUS activity under drought conditions. The overexpression of <i>OfPIP2</i> was found to enhance petal size by modulating epidermal cell dimensions in <i>Petunia</i> and tobacco. Moreover, this overexpression also bolstered drought tolerance, as evidenced by a reduction in stomatal aperture in both species. Furthermore, yeast one-hybrid (Y1H) and dual-luciferase (Dual-LUC) assays have indicated that the transcription factor OfMYB28 directly binds to the <i>OfPIP2</i> promoter, thereby regulating its expression. Together, we speculated that a module of OfMYB28-<i>OfPIP2</i> was not only involved in the enhancement of petal size but also conferred the improvement of drought tolerance in <i>O. fragrans</i>. These results contribute valuable insights into the molecular function of the <i>OfPIP2</i> gene and lay a foundation for molecular breeding strategies in <i>O. fragrans</i>.