Improvement of Water Stress Tolerance of Tuberous Begonia (Begonia×tuberhybrida) by OsmiR393a Gene Transformation

The genus Begonia is greatly affected by abiotic stresses, which lead to losses in greenhouse production and flower longevity. Obtaining more-tolerant plants is a very important breeding goal in ornamentals. To achieve abiotic tolerant Begonia×tuberhybrida, OsmiR393a, a miRNA involved in the tolerance of plants to abiotic stresses, was introduced using Agrobacterium-mediated transformation. Explants were cultured on modified MS medium supplemented with 1.0 mg/L BA, 0.5 mg/L IAA, and 5 mg/L hygromycin for transgenic selection and regeneration. Stable integration of the transgene was verified in putatively transformed plants by PCR screening. When fresh flower longevity was evaluated by the period from bloom to wilting of 3 petals, flower longevity of transgenic line was 8 d longer than control. Furthermore, 15 days after stress treatment, petals of control plants wilted, whereas transgenic lines remained. This results shows that expressing OsmiR393a could extend only flower longevity without affecting flower type under water stress in Begonia×tuberhybrida. In addition, the transgenic plants displayed lower transpiration rate, higher proline content and chlorophyll content when subjected to water stress. These results suggest OsmiR393a may improve water stress tolerance of Begonia×tuberhybrida by regulating different pathways in response to the stress conditions and miR393a is conservatized between monocotyledon and dicotyledon.