Drought Tolerance in Cotton Plants Expressing an Osmotin Gene from Tobacco

Osmotin, a PR5 family protein, is induced in plants in response to various types of biotic and abiotic challenges and is believed to provide protection to various stresses.  We investigated drought tolerance in cotton plants that were transformed with a construct containing a truncated form of osmotin gene from Nicotiana tabacum under the control of CaMV 35S promoter.  This protein, lacking the C-terminal vacuolar-sorting motif, was secreted apoplastically.  The transformants were better able to tolerate water stress induced by PEG and that as a result of dry soil conditions.  Under drought conditions, the leaves from transgenic plants exhibited higher relative water content and proline levels, while showing reduced H₂O₂ levels, lipid peroxidation and electrolyte leakage.  After experiencing a series of dry periods, the transgenic plants expressing the osmotin gene performed better in terms of most growth and developmental parameters tested.  Importantly, the fiber yield of the osmotin-transformants did not suffer as much as that of the non-transgenic plants following exposure to drought conditions.  Results from this investigation and their significance will be presented.