Enhanced Drought and Osmotic Stress Tolerance in Transgenic Potato Plants Expressing AtCDPK1, a Calcium-Dependent Protein Kinase

Growing evidence indicates that calcium-dependent protein kinases (CDPKs) are involved in many aspects of plant’s growth, development and responses to biotic and abiotic stresses. Previous researchers reported AtCDPK1 gene used as a positive regulator in salt and drought stress signaling. This study aimed to increase transgenic potatoes’ (Solanum tuberosum L. cv. Favorita) tolerance to the drought and osmotic stresses. Transgenic potato plants expressing AtCDPK1 gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter (referred to as T-plants) were successfully generated through Agrobacterium-mediated transformation. Two representative transgenic T6 and T25 lines were evaluated for enhanced tolerance to drought and osmotic stresses. The survival rates of transgenic lines T6 and T25 (67 and 54%, respectively) were higher than that of wild type (WT) plants (25%) after the drought stress. After 15 days of PEG stress, the survival rate of T6 was 45.68%, whereas that of the WT line was approximately 20%. The survival rate of transgenic lines was very higher than that of WT after 15 days of PEG stress. The content of proline and malondialdehyde (MDA) were clear difference between control and transgenic lines after the drought and osmotic stresses. After the 24 h osmotic treatment, content of proline in transgenic plants was very higher than that of the control, enhanced 26%, reached an extremely significant level (P < 0.05). MDA content in transgenic plants was lower than the control in the same period, while the biggest difference appeared at 24 h (P < 0.05), and MDA content of transgenic plants reduced 28% than the control. qRT-PCR proves that relative expressions of StP5CS and StProDH genes in the transgenic lines both increased in early period, and then decreased after PEG 6000 stress. These results suggested that enhanced AtCDPK1 expression affected the transcription of stress-associated genes and the content of proline and MDA in transgenic plants, which leads to improved tolerance ability in transgenic potatoes.