Improvement of the Hydroponic Growth and Waterlogging Tolerance of Petunias by the Introduction of vhb Gene

The coding sequence of Vitreoscilla hemoglobin ( vhb ) was cloned with PCR technique from Vitreoscilla stercoraria Pringsheim. The plant expression vector with vhb gene under the control of CaMV 35S promoter was constructed and used in the transformation of Petunia hybrida Vilm by the Agrobacterium mediated procedure. The results of PCR amplification and Southern hybridization indicated that the vhb gene had been integrated into the petunia genome and the vhb gene expression had been detected by RT_PCR amplification. In hydroponic culture the transgenic petunias grew much better than non_transgenic controls. For further analysis of hypoxia tolerance of transgenic petunia, the petunia plants with vhb gene were submerged into liquid MS medium. The transgenic plants survived in hypoxic condition and grew out of the liquid surface in a few weeks, while non_transgenic plants were still submerged and suffocated in culture solution without ability to grow out of liquid medium in submersed culture for four to five weeks. The vhb gene transformed petunia plants had been planted and tested in a simulated flooding condition, and showed obvious tolerance to waterlogging. It seems that hemoglobin gene from Vitreoscilla might have the potential use in molecular breeding for the improvement of plant resistance to hypoxia and flooding.